AI Trajectory

null

{
  "EnableConfigs": [
    "BPF_SYSCALL"
  ],
  "FocusSymbols": [
    "scalar32_min_max_lsh",
    "scalar_min_max_lsh",
    "scalar32_min_max_rsh",
    "scalar_min_max_rsh",
    "scalar32_min_max_arsh",
    "scalar_min_max_arsh",
    "is_safe_to_compute_dst_reg_range"
  ],
  "Reasoning": "The patch modifies the BPF verifier to support tracking bounds for shift operations (LSH, RSH, ARSH) when the shift amount is not a constant, but a range. This is a functional change in the highly reachable and critical BPF verifier logic, which should be fuzzed to ensure it doesn't introduce any vulnerabilities or incorrect bounds tracking.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit c8b4daa0c29a2b6907e61451d27e07e8af115dc4\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Tue Jun 23 14:01:05 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c\nindex 2abc79dbf281c2..bf247c219cab58 100644\n--- a/kernel/bpf/verifier.c\n+++ b/kernel/bpf/verifier.c\n@@ -14277,7 +14277,8 @@ static void scalar32_min_max_lsh(struct bpf_reg_state *dst_reg,\n \tstruct tnum subreg = tnum_subreg(dst_reg-\u003evar_off);\n \n \t__scalar32_min_max_lsh(dst_reg, umin_val, umax_val);\n-\tdst_reg-\u003evar_off = tnum_subreg(tnum_lshift(subreg, umin_val));\n+\tdst_reg-\u003evar_off = (umin_val == umax_val) ?\n+\t\t\t   tnum_subreg(tnum_lshift(subreg, umin_val)) : tnum_unknown;\n \t/* Not required but being careful mark reg64 bounds as unknown so\n \t * that we are forced to pick them up from tnum and zext later and\n \t * if some path skips this step we are still safe.\n@@ -14322,7 +14323,8 @@ static void scalar_min_max_lsh(struct bpf_reg_state *dst_reg,\n \t__scalar64_min_max_lsh(dst_reg, umin_val, umax_val);\n \t__scalar32_min_max_lsh(dst_reg, umin_val, umax_val);\n \n-\tdst_reg-\u003evar_off = tnum_lshift(dst_reg-\u003evar_off, umin_val);\n+\tdst_reg-\u003evar_off = (umin_val == umax_val) ?\n+\t\t\t   tnum_lshift(dst_reg-\u003evar_off, umin_val) : tnum_unknown;\n \t/* We may learn something more from the var_off */\n \t__update_reg_bounds(dst_reg);\n }\n@@ -14349,7 +14351,8 @@ static void scalar32_min_max_rsh(struct bpf_reg_state *dst_reg,\n \t * var_off of the result.\n \t */\n \n-\tdst_reg-\u003evar_off = tnum_rshift(subreg, umin_val);\n+\tdst_reg-\u003evar_off = (umin_val == umax_val) ?\n+\t\t\t   tnum_rshift(subreg, umin_val) : tnum_unknown;\n \treg_set_urange32(dst_reg, reg_u32_min(dst_reg) \u003e\u003e umax_val,\n \t\t\t reg_u32_max(dst_reg) \u003e\u003e umin_val);\n \n@@ -14377,7 +14380,8 @@ static void scalar_min_max_rsh(struct bpf_reg_state *dst_reg,\n \t * and rely on inferring new ones from the unsigned bounds and\n \t * var_off of the result.\n \t */\n-\tdst_reg-\u003evar_off = tnum_rshift(dst_reg-\u003evar_off, umin_val);\n+\tdst_reg-\u003evar_off = (umin_val == umax_val) ?\n+\t\t\t   tnum_rshift(dst_reg-\u003evar_off, umin_val) : tnum_unknown;\n \treg_set_urange64(dst_reg, reg_umin(dst_reg) \u003e\u003e umax_val,\n \t\t\t reg_umax(dst_reg) \u003e\u003e umin_val);\n \n@@ -14392,18 +14396,41 @@ static void scalar_min_max_rsh(struct bpf_reg_state *dst_reg,\n static void scalar32_min_max_arsh(struct bpf_reg_state *dst_reg,\n \t\t\t\t  struct bpf_reg_state *src_reg)\n {\n-\tu64 umin_val = reg_u32_min(src_reg);\n+\tu32 umin_shift = reg_u32_min(src_reg);\n+\tu32 umax_shift = reg_u32_max(src_reg);\n+\ts32 smin = reg_s32_min(dst_reg);\n+\ts32 smax = reg_s32_max(dst_reg);\n \n-\t/* Upon reaching here, src_known is true and\n-\t * umax_val is equal to umin_val.\n-\t * Blow away the dst_reg umin_value/umax_value and rely on\n-\t * dst_reg var_off to refine the result.\n+\t/*\n+\t * BPF_ARSH on 32-bit subregister. ARSH is a signed divide by\n+\t * 2^k (rounding toward -inf for negatives). With a non-constant\n+\t * shift in [umin, umax], the result is bounded by dividing the\n+\t * extremes of [smin, smax] by the extremes of the divisor:\n+\t *\n+\t *   smin \u003e= 0:  [smin / 2^umax, smax / 2^umin]\n+\t *   smax \u003c  0:  [smin / 2^umin, smax / 2^umax]\n+\t *   mixed:      [smin / 2^umin, smax / 2^umin]\n+\t *\n+\t * var_off is tnum_unknown since a non-constant shift prevents\n+\t * precise bit tracking.\n \t */\n-\treg_set_srange32(dst_reg,\n-\t\t\t (u32)(((s32)reg_s32_min(dst_reg)) \u003e\u003e umin_val),\n-\t\t\t (u32)(((s32)reg_s32_max(dst_reg)) \u003e\u003e umin_val));\n-\n-\tdst_reg-\u003evar_off = tnum_arshift(tnum_subreg(dst_reg-\u003evar_off), umin_val, 32);\n+\tif (umin_shift == umax_shift) {\n+\t\treg_set_srange32(dst_reg, (u32)(smin \u003e\u003e umin_shift),\n+\t\t\t\t (u32)(smax \u003e\u003e umin_shift));\n+\t\tdst_reg-\u003evar_off = tnum_arshift(tnum_subreg(dst_reg-\u003evar_off),\n+\t\t\t\t\t\tumin_shift, 32);\n+\t} else {\n+\t\tif (smin \u003e= 0)\n+\t\t\treg_set_srange32(dst_reg, (u32)(smin \u003e\u003e umax_shift),\n+\t\t\t\t\t (u32)(smax \u003e\u003e umin_shift));\n+\t\telse if (smax \u003c 0)\n+\t\t\treg_set_srange32(dst_reg, (u32)(smin \u003e\u003e umin_shift),\n+\t\t\t\t\t (u32)(smax \u003e\u003e umax_shift));\n+\t\telse\n+\t\t\treg_set_srange32(dst_reg, (u32)(smin \u003e\u003e umin_shift),\n+\t\t\t\t\t (u32)(smax \u003e\u003e umin_shift));\n+\t\tdst_reg-\u003evar_off = tnum_unknown;\n+\t}\n \n \t__mark_reg64_unbounded(dst_reg);\n \t__update_reg32_bounds(dst_reg);\n@@ -14412,15 +14439,37 @@ static void scalar32_min_max_arsh(struct bpf_reg_state *dst_reg,\n static void scalar_min_max_arsh(struct bpf_reg_state *dst_reg,\n \t\t\t\tstruct bpf_reg_state *src_reg)\n {\n-\tu64 umin_val = reg_umin(src_reg);\n+\tu64 umin_shift = reg_umin(src_reg);\n+\tu64 umax_shift = reg_umax(src_reg);\n+\ts64 smin = reg_smin(dst_reg);\n+\ts64 smax = reg_smax(dst_reg);\n \n-\t/* Upon reaching here, src_known is true and umax_val is equal\n-\t * to umin_val.\n+\t/*\n+\t * BPF_ARSH (arithmetic right shift) on 64-bit register. Signed\n+\t * divide by 2^k, rounding toward -inf for negatives. With a\n+\t * non-constant shift in [umin, umax], the result is bounded\n+\t * by dividing the extremes of [smin, smax] by the extremes\n+\t * of the divisor:\n+\t *\n+\t *   smin \u003e= 0:  [smin / 2^umax, smax / 2^umin]\n+\t *   smax \u003c  0:  [smin / 2^umin, smax / 2^umax]\n+\t *   mixed:      [smin / 2^umin, smax / 2^umin]\n+\t *\n+\t * var_off is tnum_unknown since a non-constant shift prevents\n+\t * precise bit tracking.\n \t */\n-\treg_set_srange64(dst_reg, reg_smin(dst_reg) \u003e\u003e umin_val,\n-\t\t\t reg_smax(dst_reg) \u003e\u003e umin_val);\n-\n-\tdst_reg-\u003evar_off = tnum_arshift(dst_reg-\u003evar_off, umin_val, 64);\n+\tif (umin_shift == umax_shift) {\n+\t\treg_set_srange64(dst_reg, smin \u003e\u003e umin_shift, smax \u003e\u003e umin_shift);\n+\t\tdst_reg-\u003evar_off = tnum_arshift(dst_reg-\u003evar_off, umin_shift, 64);\n+\t} else {\n+\t\tif (smin \u003e= 0)\n+\t\t\treg_set_srange64(dst_reg, smin \u003e\u003e umax_shift, smax \u003e\u003e umin_shift);\n+\t\telse if (smax \u003c 0)\n+\t\t\treg_set_srange64(dst_reg, smin \u003e\u003e umin_shift, smax \u003e\u003e umax_shift);\n+\t\telse\n+\t\t\treg_set_srange64(dst_reg, smin \u003e\u003e umin_shift, smax \u003e\u003e umin_shift);\n+\t\tdst_reg-\u003evar_off = tnum_unknown;\n+\t}\n \n \t/* Its not easy to operate on alu32 bounds here because it depends\n \t * on bits being shifted in from upper 32-bits. Take easy way out\n@@ -14516,14 +14565,14 @@ static bool is_safe_to_compute_dst_reg_range(struct bpf_insn *insn,\n \tcase BPF_MOD:\n \t\treturn src_is_const;\n \n-\t/* Shift operators range is only computable if shift dimension operand\n-\t * is a constant. Shifts greater than 31 or 63 are undefined. This\n-\t * includes shifts by a negative number.\n+\t/*\n+\t * Shifts greater than 31 or 63 are implementation-defined behaviour.\n+\t * This includes shifts by a negative number.\n \t */\n \tcase BPF_LSH:\n \tcase BPF_RSH:\n \tcase BPF_ARSH:\n-\t\treturn (src_is_const \u0026\u0026 reg_umax(src_reg) \u003c insn_bitness);\n+\t\treturn reg_umax(src_reg) \u003c insn_bitness;\n \tdefault:\n \t\treturn false;\n \t}\ndiff --git a/tools/testing/selftests/bpf/progs/verifier_bounds.c b/tools/testing/selftests/bpf/progs/verifier_bounds.c\nindex bc038ac2df98e2..52ae3dc593600f 100644\n--- a/tools/testing/selftests/bpf/progs/verifier_bounds.c\n+++ b/tools/testing/selftests/bpf/progs/verifier_bounds.c\n@@ -482,6 +482,173 @@ l0_%=:\t/* exit */\t\t\t\t\t\\\n \t: __clobber_all);\n }\n \n+#define SHIFT_NON_CONST_SRC_TEST(name, desc, rand, dst, src, op, src_add, dst_init, msg) \\\n+\tSEC(\"socket\")\t\t\t\t\t\\\n+\t__description(desc)\t\t\t\t\\\n+\t__success __log_level(2)\t\t\t\\\n+\t__msg(#dst \" \" op \" \" #src \" {{.*}}; \" msg)\t\\\n+\t__naked void name(void)\t\t\t\t\\\n+\t{\t\t\t\t\t\t\\\n+\t\tasm volatile (\"\t\t\t\t\\\n+\t\tcall %[bpf_get_prandom_u32];\t\t\\\n+\t\t\" #src \" = \" #rand \";\t\t\t\\\n+\t\t\" #src \" \u0026= 3;\t\t\t\t\\\n+\t\t\" #src \" += \" #src_add \";\t\t\\\n+\t\t\" #dst \" = \" #dst_init \";\t\t\\\n+\t\t\" #dst \" \" op \" \" #src \";\t\t\\\n+\t\texit;\t\t\t\t\t\\\n+\"\t\t:: __imm(bpf_get_prandom_u32)\t\t\\\n+\t\t: __clobber_all);\t\t\t\\\n+\t}\n+\n+SHIFT_NON_CONST_SRC_TEST(\n+\tshift_with_non_const_src_lsh_32,\n+\t\"bounds check after non-const 32-bit left shift\",\n+\tw0, w1, w2, \"\u003c\u003c=\", 1, 1,\n+\t\"R1=scalar(smin=umin=smin32=umin32=2,smax=umax=smax32=umax32=16,var_off=(0x0; 0x1f))\"\n+)\n+\n+SHIFT_NON_CONST_SRC_TEST(\n+\tshift_with_non_const_src_lsh_32_overflow,\n+\t\"bounds check after non-const 32-bit lsh with overflow src\",\n+\tw0, w1, w2, \"\u003c\u003c=\", 32, 1,\n+\t\"R1=scalar() R2=scalar(smin=umin=smin32=umin32=32,smax=umax=smax32=umax32=35,var_off=(0x20; 0x3))\"\n+)\n+\n+SHIFT_NON_CONST_SRC_TEST(\n+\tshift_with_non_const_src_rsh_32,\n+\t\"bounds check after non-const 32-bit right shift\",\n+\tw0, w1, w2, \"\u003e\u003e=\", 1, 0xff,\n+\t\"R1=scalar(smin=umin=smin32=umin32=15,smax=umax=smax32=umax32=127,var_off=(0x0; 0x7f))\"\n+)\n+\n+SHIFT_NON_CONST_SRC_TEST(\n+\tshift_with_non_const_src_rsh_32_overflow,\n+\t\"bounds check after non-const 32-bit rsh with overflow src\",\n+\tw0, w1, w2, \"\u003e\u003e=\", 32, 1,\n+\t\"R1=scalar() R2=scalar(smin=umin=smin32=umin32=32,smax=umax=smax32=umax32=35,var_off=(0x20; 0x3))\"\n+)\n+\n+SHIFT_NON_CONST_SRC_TEST(\n+\tshift_with_non_const_src_arsh_32,\n+\t\"bounds check after non-const 32-bit arithmetic shift\",\n+\tw0, w1, w2, \"s\u003e\u003e=\", 1, -8,\n+\t\"R1=scalar(smin=umin=umin32=0xfffffffc,smax=umax=0xffffffff,smin32=-4,smax32=-1,var_off=(0xfffffffc; 0x3)) R2=scalar(smin=umin=smin32=umin32=1,smax=umax=smax32=umax32=4,var_off=(0x0; 0x7))\"\n+)\n+\n+SHIFT_NON_CONST_SRC_TEST(\n+\tshift_with_non_const_src_arsh_32_overflow,\n+\t\"bounds check after non-const 32-bit arsh with overflow src\",\n+\tw0, w1, w2, \"s\u003e\u003e=\", 32, 1,\n+\t\"R1=scalar() R2=scalar(smin=umin=smin32=umin32=32,smax=umax=smax32=umax32=35,var_off=(0x20; 0x3))\"\n+)\n+\n+SHIFT_NON_CONST_SRC_TEST(\n+\tshift_with_non_const_src_lsh_64,\n+\t\"bounds check after non-const 64-bit left shift\",\n+\tr0, r1, r2, \"\u003c\u003c=\", 1, 1,\n+\t\"R1=scalar(smin=umin=smin32=umin32=2,smax=umax=smax32=umax32=16,var_off=(0x0; 0x1f))\"\n+)\n+\n+SHIFT_NON_CONST_SRC_TEST(\n+\tshift_with_non_const_src_lsh_64_overflow,\n+\t\"bounds check after non-const 64-bit lsh with overflow src\",\n+\tr0, r1, r2, \"\u003c\u003c=\", 64, 1,\n+\t\"R1=scalar() R2=scalar(smin=umin=smin32=umin32=64,smax=umax=smax32=umax32=67,var_off=(0x40; 0x3))\"\n+)\n+\n+SHIFT_NON_CONST_SRC_TEST(\n+\tshift_with_non_const_src_rsh_64,\n+\t\"bounds check after non-const 64-bit right shift\",\n+\tr0, r1, r2, \"\u003e\u003e=\", 1, 0xff,\n+\t\"R1=scalar(smin=umin=smin32=umin32=15,smax=umax=smax32=umax32=127,var_off=(0x0; 0x7f))\"\n+)\n+\n+SHIFT_NON_CONST_SRC_TEST(\n+\tshift_with_non_const_src_rsh_64_overflow,\n+\t\"bounds check after non-const 64-bit rsh with overflow src\",\n+\tr0, r1, r2, \"\u003e\u003e=\", 64, 1,\n+\t\"R1=scalar() R2=scalar(smin=umin=smin32=umin32=64,smax=umax=smax32=umax32=67,var_off=(0x40; 0x3))\"\n+)\n+\n+SHIFT_NON_CONST_SRC_TEST(\n+\tshift_with_non_const_src_arsh_64,\n+\t\"bounds check after non-const 64-bit arithmetic shift\",\n+\tr0, r1, r2, \"s\u003e\u003e=\", 1, -8,\n+\t\"R1=scalar(smin=smin32=-4,smax=smax32=-1,umin=0xfffffffffffffffc,umin32=0xfffffffc,var_off=(0xfffffffffffffffc; 0x3)) R2=scalar(smin=umin=smin32=umin32=1,smax=umax=smax32=umax32=4,var_off=(0x0; 0x7))\"\n+)\n+\n+SHIFT_NON_CONST_SRC_TEST(\n+\tshift_with_non_const_src_arsh_64_overflow,\n+\t\"bounds check after non-const 64-bit arsh with overflow src\",\n+\tr0, r1, r2, \"s\u003e\u003e=\", 64, 1,\n+\t\"R1=scalar() R2=scalar(smin=umin=smin32=umin32=64,smax=umax=smax32=umax32=67,var_off=(0x40; 0x3))\"\n+)\n+\n+#define SHIFT_ARSH_DST_RANGE_TEST(name, desc, rand, dst, src, dst_mask, dst_delta, msg) \\\n+\tSEC(\"socket\")\t\t\t\t\t\\\n+\t__description(desc)\t\t\t\t\\\n+\t__success __log_level(2)\t\t\t\\\n+\t__msg(#dst \" s\u003e\u003e= \" #src \" {{.*}}; {{.*}} \" msg)\\\n+\t__naked void name(void)\t\t\t\t\\\n+\t{\t\t\t\t\t\t\\\n+\t\tasm volatile (\"\t\t\t\t\\\n+\t\tcall %[bpf_get_prandom_u32];\t\t\\\n+\t\t\" #dst \" = \" #rand \";\t\t\t\\\n+\t\t\" #dst \" \u0026= \" #dst_mask \";\t\t\\\n+\t\t\" #dst \" += \" #dst_delta \";\t\t\\\n+\t\tcall %[bpf_get_prandom_u32];\t\t\\\n+\t\t\" #src \" = \" #rand \";\t\t\t\\\n+\t\t\" #src \" \u0026= 1;\t\t\t\t\\\n+\t\t\" #src \" += 1;\t\t\t\t\\\n+\t\t\" #dst \" s\u003e\u003e= \" #src \";\t\t\t\\\n+\t\texit;\t\t\t\t\t\\\n+\"\t\t:: __imm(bpf_get_prandom_u32)\t\t\\\n+\t\t: __clobber_all);\t\t\t\\\n+\t}\n+\n+SHIFT_ARSH_DST_RANGE_TEST(\n+\tshift_with_non_const_src_arsh_32_pos,\n+\t\"bounds check after non-const 32-bit arsh with positive dst\",\n+\tw0, w6, w2, 7, 1,\n+\t\"R6=scalar(smin=smin32=0,smax=umax=smax32=umax32=4,var_off=(0x0; 0x7))\"\n+)\n+\n+SHIFT_ARSH_DST_RANGE_TEST(\n+\tshift_with_non_const_src_arsh_32_mixed,\n+\t\"bounds check after non-const 32-bit arsh with mixed-sign dst\",\n+\tw0, w6, w2, 15, -8,\n+\t\"R6=scalar(smin=0,smax=umax=0xffffffff,smin32=-4,smax32=3,var_off=(0x0; 0xffffffff))\"\n+)\n+\n+SHIFT_ARSH_DST_RANGE_TEST(\n+\tshift_with_non_const_src_arsh_32_neg,\n+\t\"bounds check after non-const 32-bit arsh with negative dst\",\n+\tw0, w6, w2, 8, -16,\n+\t\"R6=scalar(smin=umin=umin32=0xfffffff8,smax=umax=umax32=0xfffffffe,smin32=-8,smax32=-2,var_off=(0xfffffff8; 0x7))\"\n+)\n+\n+SHIFT_ARSH_DST_RANGE_TEST(\n+\tshift_with_non_const_src_arsh_64_pos,\n+\t\"bounds check after non-const 64-bit arsh with positive dst\",\n+\tr0, r6, r2, 7, 1,\n+\t\"R6=scalar(smin=smin32=0,smax=umax=smax32=umax32=4,var_off=(0x0; 0x7))\"\n+)\n+\n+SHIFT_ARSH_DST_RANGE_TEST(\n+\tshift_with_non_const_src_arsh_64_mixed,\n+\t\"bounds check after non-const 64-bit arsh with mixed-sign dst\",\n+\tr0, r6, r2, 15, -8,\n+\t\"R6=scalar(smin=smin32=-4,smax=smax32=3)\"\n+)\n+\n+SHIFT_ARSH_DST_RANGE_TEST(\n+\tshift_with_non_const_src_arsh_64_neg,\n+\t\"bounds check after non-const 64-bit arsh with negative dst\",\n+\tr0, r6, r2, 8, -16,\n+\t\"R6=scalar(smin=smin32=-8,smax=smax32=-2,umin=0xfffffffffffffff8,umax=0xfffffffffffffffe,umin32=0xfffffff8,umax32=0xfffffffe,var_off=(0xfffffffffffffff8; 0x7))\"\n+)\n+\n SEC(\"socket\")\n __description(\"bounds check after 32-bit right shift with 64-bit input\")\n __failure __msg(\"math between map_value pointer and 4294967294 is not allowed\")\n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "BPF_SYSCALL"
  ],
  "FocusSymbols": [
    "scalar32_min_max_lsh",
    "scalar_min_max_lsh",
    "scalar32_min_max_rsh",
    "scalar_min_max_rsh",
    "scalar32_min_max_arsh",
    "scalar_min_max_arsh",
    "is_safe_to_compute_dst_reg_range"
  ],
  "Reasoning": "The patch modifies the BPF verifier to support tracking bounds for shift operations (LSH, RSH, ARSH) when the shift amount is not a constant, but a range. This is a functional change in the highly reachable and critical BPF verifier logic, which should be fuzzed to ensure it doesn't introduce any vulnerabilities or incorrect bounds tracking.",
  "WorthFuzzing": true
}

You are an expert Linux kernel maintainer.
Your job is to review a provided patch series and determine
if it makes functional changes to the kernel that should be fuzzed.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively
use your code access tools to examine the actual source code and confirm any assumptions.

Return WorthFuzzing=false if the patch only contains:
- Modifications to Documentation/, Kconfig files, or code comments.
- Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints.
- Changes to numeric constants or macros that do not functionally alter execution flow.
- Code paths that are impossible to reach in virtualized environments like GCE or QEMU,
even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim).

If it modifies reachable core kernel logic, drivers, or architectures, use your code search
tools to verify the code can be executed, then return WorthFuzzing=true.

When returning WorthFuzzing=true, you MUST ALSO:
1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols.
   Avoid listing generic hot-path functions to prevent skewed test distributions.
2. Identify any specific CONFIG_ options required to properly test this new/modified feature.
   Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions.
   Do not list too generic configs (we already have them enabled). Only list those that
   specifically cover the modified code. List them in the EnableConfigs output array,
   and DO NOT add a 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4").
Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

For your convenience, here is the diff of the changes:
commit c8b4daa0c29a2b6907e61451d27e07e8af115dc4
Author: syz-cluster <triage@syzkaller.com>
Date:   Tue Jun 23 14:01:05 2026 +0000

    syz-cluster: applied patch under review

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 2abc79dbf281c2..bf247c219cab58 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -14277,7 +14277,8 @@ static void scalar32_min_max_lsh(struct bpf_reg_state *dst_reg,
 	struct tnum subreg = tnum_subreg(dst_reg->var_off);
 
 	__scalar32_min_max_lsh(dst_reg, umin_val, umax_val);
-	dst_reg->var_off = tnum_subreg(tnum_lshift(subreg, umin_val));
+	dst_reg->var_off = (umin_val == umax_val) ?
+			   tnum_subreg(tnum_lshift(subreg, umin_val)) : tnum_unknown;
 	/* Not required but being careful mark reg64 bounds as unknown so
 	 * that we are forced to pick them up from tnum and zext later and
 	 * if some path skips this step we are still safe.
@@ -14322,7 +14323,8 @@ static void scalar_min_max_lsh(struct bpf_reg_state *dst_reg,
 	__scalar64_min_max_lsh(dst_reg, umin_val, umax_val);
 	__scalar32_min_max_lsh(dst_reg, umin_val, umax_val);
 
-	dst_reg->var_off = tnum_lshift(dst_reg->var_off, umin_val);
+	dst_reg->var_off = (umin_val == umax_val) ?
+			   tnum_lshift(dst_reg->var_off, umin_val) : tnum_unknown;
 	/* We may learn something more from the var_off */
 	__update_reg_bounds(dst_reg);
 }
@@ -14349,7 +14351,8 @@ static void scalar32_min_max_rsh(struct bpf_reg_state *dst_reg,
 	 * var_off of the result.
 	 */
 
-	dst_reg->var_off = tnum_rshift(subreg, umin_val);
+	dst_reg->var_off = (umin_val == umax_val) ?
+			   tnum_rshift(subreg, umin_val) : tnum_unknown;
 	reg_set_urange32(dst_reg, reg_u32_min(dst_reg) >> umax_val,
 			 reg_u32_max(dst_reg) >> umin_val);
 
@@ -14377,7 +14380,8 @@ static void scalar_min_max_rsh(struct bpf_reg_state *dst_reg,
 	 * and rely on inferring new ones from the unsigned bounds and
 	 * var_off of the result.
 	 */
-	dst_reg->var_off = tnum_rshift(dst_reg->var_off, umin_val);
+	dst_reg->var_off = (umin_val == umax_val) ?
+			   tnum_rshift(dst_reg->var_off, umin_val) : tnum_unknown;
 	reg_set_urange64(dst_reg, reg_umin(dst_reg) >> umax_val,
 			 reg_umax(dst_reg) >> umin_val);
 
@@ -14392,18 +14396,41 @@ static void scalar_min_max_rsh(struct bpf_reg_state *dst_reg,
 static void scalar32_min_max_arsh(struct bpf_reg_state *dst_reg,
 				  struct bpf_reg_state *src_reg)
 {
-	u64 umin_val = reg_u32_min(src_reg);
+	u32 umin_shift = reg_u32_min(src_reg);
+	u32 umax_shift = reg_u32_max(src_reg);
+	s32 smin = reg_s32_min(dst_reg);
+	s32 smax = reg_s32_max(dst_reg);
 
-	/* Upon reaching here, src_known is true and
-	 * umax_val is equal to umin_val.
-	 * Blow away the dst_reg umin_value/umax_value and rely on
-	 * dst_reg var_off to refine the result.
+	/*
+	 * BPF_ARSH on 32-bit subregister. ARSH is a signed divide by
+	 * 2^k (rounding toward -inf for negatives). With a non-constant
+	 * shift in [umin, umax], the result is bounded by dividing the
+	 * extremes of [smin, smax] by the extremes of the divisor:
+	 *
+	 *   smin >= 0:  [smin / 2^umax, smax / 2^umin]
+	 *   smax <  0:  [smin / 2^umin, smax / 2^umax]
+	 *   mixed:      [smin / 2^umin, smax / 2^umin]
+	 *
+	 * var_off is tnum_unknown since a non-constant shift prevents
+	 * precise bit tracking.
 	 */
-	reg_set_srange32(dst_reg,
-			 (u32)(((s32)reg_s32_min(dst_reg)) >> umin_val),
-			 (u32)(((s32)reg_s32_max(dst_reg)) >> umin_val));
-
-	dst_reg->var_off = tnum_arshift(tnum_subreg(dst_reg->var_off), umin_val, 32);
+	if (umin_shift == umax_shift) {
+		reg_set_srange32(dst_reg, (u32)(smin >> umin_shift),
+				 (u32)(smax >> umin_shift));
+		dst_reg->var_off = tnum_arshift(tnum_subreg(dst_reg->var_off),
+						umin_shift, 32);
+	} else {
+		if (smin >= 0)
+			reg_set_srange32(dst_reg, (u32)(smin >> umax_shift),
+					 (u32)(smax >> umin_shift));
+		else if (smax < 0)
+			reg_set_srange32(dst_reg, (u32)(smin >> umin_shift),
+					 (u32)(smax >> umax_shift));
+		else
+			reg_set_srange32(dst_reg, (u32)(smin >> umin_shift),
+					 (u32)(smax >> umin_shift));
+		dst_reg->var_off = tnum_unknown;
+	}
 
 	__mark_reg64_unbounded(dst_reg);
 	__update_reg32_bounds(dst_reg);
@@ -14412,15 +14439,37 @@ static void scalar32_min_max_arsh(struct bpf_reg_state *dst_reg,
 static void scalar_min_max_arsh(struct bpf_reg_state *dst_reg,
 				struct bpf_reg_state *src_reg)
 {
-	u64 umin_val = reg_umin(src_reg);
+	u64 umin_shift = reg_umin(src_reg);
+	u64 umax_shift = reg_umax(src_reg);
+	s64 smin = reg_smin(dst_reg);
+	s64 smax = reg_smax(dst_reg);
 
-	/* Upon reaching here, src_known is true and umax_val is equal
-	 * to umin_val.
+	/*
+	 * BPF_ARSH (arithmetic right shift) on 64-bit register. Signed
+	 * divide by 2^k, rounding toward -inf for negatives. With a
+	 * non-constant shift in [umin, umax], the result is bounded
+	 * by dividing the extremes of [smin, smax] by the extremes
+	 * of the divisor:
+	 *
+	 *   smin >= 0:  [smin / 2^umax, smax / 2^umin]
+	 *   smax <  0:  [smin / 2^umin, smax / 2^umax]
+	 *   mixed:      [smin / 2^umin, smax / 2^umin]
+	 *
+	 * var_off is tnum_unknown since a non-constant shift prevents
+	 * precise bit tracking.
 	 */
-	reg_set_srange64(dst_reg, reg_smin(dst_reg) >> umin_val,
-			 reg_smax(dst_reg) >> umin_val);
-
-	dst_reg->var_off = tnum_arshift(dst_reg->var_off, umin_val, 64);
+	if (umin_shift == umax_shift) {
+		reg_set_srange64(dst_reg, smin >> umin_shift, smax >> umin_shift);
+		dst_reg->var_off = tnum_arshift(dst_reg->var_off, umin_shift, 64);
+	} else {
+		if (smin >= 0)
+			reg_set_srange64(dst_reg, smin >> umax_shift, smax >> umin_shift);
+		else if (smax < 0)
+			reg_set_srange64(dst_reg, smin >> umin_shift, smax >> umax_shift);
+		else
+			reg_set_srange64(dst_reg, smin >> umin_shift, smax >> umin_shift);
+		dst_reg->var_off = tnum_unknown;
+	}
 
 	/* Its not easy to operate on alu32 bounds here because it depends
 	 * on bits being shifted in from upper 32-bits. Take easy way out
@@ -14516,14 +14565,14 @@ static bool is_safe_to_compute_dst_reg_range(struct bpf_insn *insn,
 	case BPF_MOD:
 		return src_is_const;
 
-	/* Shift operators range is only computable if shift dimension operand
-	 * is a constant. Shifts greater than 31 or 63 are undefined. This
-	 * includes shifts by a negative number.
+	/*
+	 * Shifts greater than 31 or 63 are implementation-defined behaviour.
+	 * This includes shifts by a negative number.
 	 */
 	case BPF_LSH:
 	case BPF_RSH:
 	case BPF_ARSH:
-		return (src_is_const && reg_umax(src_reg) < insn_bitness);
+		return reg_umax(src_reg) < insn_bitness;
 	default:
 		return false;
 	}
diff --git a/tools/testing/selftests/bpf/progs/verifier_bounds.c b/tools/testing/selftests/bpf/progs/verifier_bounds.c
index bc038ac2df98e2..52ae3dc593600f 100644
--- a/tools/testing/selftests/bpf/progs/verifier_bounds.c
+++ b/tools/testing/selftests/bpf/progs/verifier_bounds.c
@@ -482,6 +482,173 @@ l0_%=:	/* exit */					\
 	: __clobber_all);
 }
 
+#define SHIFT_NON_CONST_SRC_TEST(name, desc, rand, dst, src, op, src_add, dst_init, msg) \
+	SEC("socket")					\
+	__description(desc)				\
+	__success __log_level(2)			\
+	__msg(#dst " " op " " #src " {{.*}}; " msg)	\
+	__naked void name(void)				\
+	{						\
+		asm volatile ("				\
+		call %[bpf_get_prandom_u32];		\
+		" #src " = " #rand ";			\
+		" #src " &= 3;				\
+		" #src " += " #src_add ";		\
+		" #dst " = " #dst_init ";		\
+		" #dst " " op " " #src ";		\
+		exit;					\
+"		:: __imm(bpf_get_prandom_u32)		\
+		: __clobber_all);			\
+	}
+
+SHIFT_NON_CONST_SRC_TEST(
+	shift_with_non_const_src_lsh_32,
+	"bounds check after non-const 32-bit left shift",
+	w0, w1, w2, "<<=", 1, 1,
+	"R1=scalar(smin=umin=smin32=umin32=2,smax=umax=smax32=umax32=16,var_off=(0x0; 0x1f))"
+)
+
+SHIFT_NON_CONST_SRC_TEST(
+	shift_with_non_const_src_lsh_32_overflow,
+	"bounds check after non-const 32-bit lsh with overflow src",
+	w0, w1, w2, "<<=", 32, 1,
+	"R1=scalar() R2=scalar(smin=umin=smin32=umin32=32,smax=umax=smax32=umax32=35,var_off=(0x20; 0x3))"
+)
+
+SHIFT_NON_CONST_SRC_TEST(
+	shift_with_non_const_src_rsh_32,
+	"bounds check after non-const 32-bit right shift",
+	w0, w1, w2, ">>=", 1, 0xff,
+	"R1=scalar(smin=umin=smin32=umin32=15,smax=umax=smax32=umax32=127,var_off=(0x0; 0x7f))"
+)
+
+SHIFT_NON_CONST_SRC_TEST(
+	shift_with_non_const_src_rsh_32_overflow,
+	"bounds check after non-const 32-bit rsh with overflow src",
+	w0, w1, w2, ">>=", 32, 1,
+	"R1=scalar() R2=scalar(smin=umin=smin32=umin32=32,smax=umax=smax32=umax32=35,var_off=(0x20; 0x3))"
+)
+
+SHIFT_NON_CONST_SRC_TEST(
+	shift_with_non_const_src_arsh_32,
+	"bounds check after non-const 32-bit arithmetic shift",
+	w0, w1, w2, "s>>=", 1, -8,
+	"R1=scalar(smin=umin=umin32=0xfffffffc,smax=umax=0xffffffff,smin32=-4,smax32=-1,var_off=(0xfffffffc; 0x3)) R2=scalar(smin=umin=smin32=umin32=1,smax=umax=smax32=umax32=4,var_off=(0x0; 0x7))"
+)
+
+SHIFT_NON_CONST_SRC_TEST(
+	shift_with_non_const_src_arsh_32_overflow,
+	"bounds check after non-const 32-bit arsh with overflow src",
+	w0, w1, w2, "s>>=", 32, 1,
+	"R1=scalar() R2=scalar(smin=umin=smin32=umin32=32,smax=umax=smax32=umax32=35,var_off=(0x20; 0x3))"
+)
+
+SHIFT_NON_CONST_SRC_TEST(
+	shift_with_non_const_src_lsh_64,
+	"bounds check after non-const 64-bit left shift",
+	r0, r1, r2, "<<=", 1, 1,
+	"R1=scalar(smin=umin=smin32=umin32=2,smax=umax=smax32=umax32=16,var_off=(0x0; 0x1f))"
+)
+
+SHIFT_NON_CONST_SRC_TEST(
+	shift_with_non_const_src_lsh_64_overflow,
+	"bounds check after non-const 64-bit lsh with overflow src",
+	r0, r1, r2, "<<=", 64, 1,
+	"R1=scalar() R2=scalar(smin=umin=smin32=umin32=64,smax=umax=smax32=umax32=67,var_off=(0x40; 0x3))"
+)
+
+SHIFT_NON_CONST_SRC_TEST(
+	shift_with_non_const_src_rsh_64,
+	"bounds check after non-const 64-bit right shift",
+	r0, r1, r2, ">>=", 1, 0xff,
+	"R1=scalar(smin=umin=smin32=umin32=15,smax=umax=smax32=umax32=127,var_off=(0x0; 0x7f))"
+)
+
+SHIFT_NON_CONST_SRC_TEST(
+	shift_with_non_const_src_rsh_64_overflow,
+	"bounds check after non-const 64-bit rsh with overflow src",
+	r0, r1, r2, ">>=", 64, 1,
+	"R1=scalar() R2=scalar(smin=umin=smin32=umin32=64,smax=umax=smax32=umax32=67,var_off=(0x40; 0x3))"
+)
+
+SHIFT_NON_CONST_SRC_TEST(
+	shift_with_non_const_src_arsh_64,
+	"bounds check after non-const 64-bit arithmetic shift",
+	r0, r1, r2, "s>>=", 1, -8,
+	"R1=scalar(smin=smin32=-4,smax=smax32=-1,umin=0xfffffffffffffffc,umin32=0xfffffffc,var_off=(0xfffffffffffffffc; 0x3)) R2=scalar(smin=umin=smin32=umin32=1,smax=umax=smax32=umax32=4,var_off=(0x0; 0x7))"
+)
+
+SHIFT_NON_CONST_SRC_TEST(
+	shift_with_non_const_src_arsh_64_overflow,
+	"bounds check after non-const 64-bit arsh with overflow src",
+	r0, r1, r2, "s>>=", 64, 1,
+	"R1=scalar() R2=scalar(smin=umin=smin32=umin32=64,smax=umax=smax32=umax32=67,var_off=(0x40; 0x3))"
+)
+
+#define SHIFT_ARSH_DST_RANGE_TEST(name, desc, rand, dst, src, dst_mask, dst_delta, msg) \
+	SEC("socket")					\
+	__description(desc)				\
+	__success __log_level(2)			\
+	__msg(#dst " s>>= " #src " {{.*}}; {{.*}} " msg)\
+	__naked void name(void)				\
+	{						\
+		asm volatile ("				\
+		call %[bpf_get_prandom_u32];		\
+		" #dst " = " #rand ";			\
+		" #dst " &= " #dst_mask ";		\
+		" #dst " += " #dst_delta ";		\
+		call %[bpf_get_prandom_u32];		\
+		" #src " = " #rand ";			\
+		" #src " &= 1;				\
+		" #src " += 1;				\
+		" #dst " s>>= " #src ";			\
+		exit;					\
+"		:: __imm(bpf_get_prandom_u32)		\
+		: __clobber_all);			\
+	}
+
+SHIFT_ARSH_DST_RANGE_TEST(
+	shift_with_non_const_src_arsh_32_pos,
+	"bounds check after non-const 32-bit arsh with positive dst",
+	w0, w6, w2, 7, 1,
+	"R6=scalar(smin=smin32=0,smax=umax=smax32=umax32=4,var_off=(0x0; 0x7))"
+)
+
+SHIFT_ARSH_DST_RANGE_TEST(
+	shift_with_non_const_src_arsh_32_mixed,
+	"bounds check after non-const 32-bit arsh with mixed-sign dst",
+	w0, w6, w2, 15, -8,
+	"R6=scalar(smin=0,smax=umax=0xffffffff,smin32=-4,smax32=3,var_off=(0x0; 0xffffffff))"
+)
+
+SHIFT_ARSH_DST_RANGE_TEST(
+	shift_with_non_const_src_arsh_32_neg,
+	"bounds check after non-const 32-bit arsh with negative dst",
+	w0, w6, w2, 8, -16,
+	"R6=scalar(smin=umin=umin32=0xfffffff8,smax=umax=umax32=0xfffffffe,smin32=-8,smax32=-2,var_off=(0xfffffff8; 0x7))"
+)
+
+SHIFT_ARSH_DST_RANGE_TEST(
+	shift_with_non_const_src_arsh_64_pos,
+	"bounds check after non-const 64-bit arsh with positive dst",
+	r0, r6, r2, 7, 1,
+	"R6=scalar(smin=smin32=0,smax=umax=smax32=umax32=4,var_off=(0x0; 0x7))"
+)
+
+SHIFT_ARSH_DST_RANGE_TEST(
+	shift_with_non_const_src_arsh_64_mixed,
+	"bounds check after non-const 64-bit arsh with mixed-sign dst",
+	r0, r6, r2, 15, -8,
+	"R6=scalar(smin=smin32=-4,smax=smax32=3)"
+)
+
+SHIFT_ARSH_DST_RANGE_TEST(
+	shift_with_non_const_src_arsh_64_neg,
+	"bounds check after non-const 64-bit arsh with negative dst",
+	r0, r6, r2, 8, -16,
+	"R6=scalar(smin=smin32=-8,smax=smax32=-2,umin=0xfffffffffffffff8,umax=0xfffffffffffffffe,umin32=0xfffffff8,umax32=0xfffffffe,var_off=(0xfffffffffffffff8; 0x7))"
+)
+
 SEC("socket")
 __description("bounds check after 32-bit right shift with 64-bit input")
 __failure __msg("math between map_value pointer and 4294967294 is not allowed")

gemini-3.1-pro-preview

null

null

							input: 7883
							output: 29
							thoughts: 355
						

**My Assessment of the BPF Verifier Patch**

Okay, so this patch is digging into `kernel/bpf/verifier.c`.  Specifically, it's about how the BPF verifier handles bounds tracking for shift operations – left shift (LSH), right shift (RSH), and arithmetic right shift (ARSH) – when the shift *amount* isn't a fixed constant, but a range.  Previously, I recall the verifier needed a constant shift amount to accurately determine the range of the destination register.  This change seems to relax that requirement, allowing for a shift amount range (where `umin_val != umax_val`) and adjusting the bounds calculation accordingly.

The key is that the `is_safe_to_compute_dst_reg_range` function is also being updated to now return true for non-constant shifts, as long as the maximum shift amount is less than the bit width, either 32 or 64. That's a clever optimization, I can see how it helps to compute these bounds correctly.

This is a fundamental functional change within the BPF verifier. The verifier is an incredibly critical and frequently-accessed component of the kernel, so this definitely warrants serious fuzzing. We have to be meticulous here.

Now, let's nail down the exact functions that are getting modified. Looks like it's impacting these: `scalar32_min_max_lsh`, `scalar_min_max_lsh`, `scalar32_min_max_rsh`, `scalar_min_max_rsh`, `scalar32_min_max_arsh`, `scalar_min_max_arsh`, and also `is_safe_to_compute_dst_reg_range`. Got it.

For configuration, `BPF_SYSCALL` seems to be the obvious one. We need to be absolutely sure this is the only one required for the relevant code to be compiled. I will confirm that `kernel/bpf/verifier.c` is compiled when `CONFIG_BPF_SYSCALL` is enabled. Better safe than sorry.

{
  "Expression": "verifier.o",
  "PathPrefix": "kernel/bpf/Makefile"
}

{
  "Output": "kernel/bpf/Makefile=7=CFLAGS_core.o += -Wno-override-init $(cflags-nogcse-yy)\nkernel/bpf/Makefile-8-\nkernel/bpf/Makefile:9:obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o cnum.o log.o token.o liveness.o const_fold.o\nkernel/bpf/Makefile-10-obj-$(CONFIG_BPF_SYSCALL) += bpf_iter.o map_iter.o task_iter.o prog_iter.o link_iter.o\n"
}

gemini-3.1-pro-preview

null

null

							input: 8883
							output: 38
							thoughts: 35
						

**Confirming the BPF Syscall Configuration**

Alright, yes, based on what I know, `CONFIG_BPF_SYSCALL` is definitely the key configuration option we're looking for. That seems right. Now, let's dive in and confirm this. I need to take a look at the functions that have been modified within `kernel/bpf/verifier.c`. This will give me a better understanding of how the code is structured and how this particular configuration impacts the BPF verifier, specifically. I want to see exactly how things have been updated and where.

{
  "Expression": "scalar32_min_max_lsh",
  "PathPrefix": "kernel/bpf/verifier.c"
}

{
  "Output": "kernel/bpf/verifier.c=14239=static void scalar_min_max_xor(struct bpf_reg_state *dst_reg,\n--\nkernel/bpf/verifier.c-14256-\nkernel/bpf/verifier.c:14257:static void __scalar32_min_max_lsh(struct bpf_reg_state *dst_reg,\nkernel/bpf/verifier.c-14258-\t\t\t\t   u64 umin_val, u64 umax_val)\n--\nkernel/bpf/verifier.c-14270-\nkernel/bpf/verifier.c:14271:static void scalar32_min_max_lsh(struct bpf_reg_state *dst_reg,\nkernel/bpf/verifier.c-14272-\t\t\t\t struct bpf_reg_state *src_reg)\n--\nkernel/bpf/verifier.c-14278-\nkernel/bpf/verifier.c:14279:\t__scalar32_min_max_lsh(dst_reg, umin_val, umax_val);\nkernel/bpf/verifier.c-14280-\tdst_reg-\u003evar_off = (umin_val == umax_val) ?\n--\nkernel/bpf/verifier.c=14316=static void scalar_min_max_lsh(struct bpf_reg_state *dst_reg,\n--\nkernel/bpf/verifier.c-14323-\t__scalar64_min_max_lsh(dst_reg, umin_val, umax_val);\nkernel/bpf/verifier.c:14324:\t__scalar32_min_max_lsh(dst_reg, umin_val, umax_val);\nkernel/bpf/verifier.c-14325-\n--\nkernel/bpf/verifier.c=14614=static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,\n--\nkernel/bpf/verifier.c-14730-\t\tif (alu32)\nkernel/bpf/verifier.c:14731:\t\t\tscalar32_min_max_lsh(dst_reg, \u0026src_reg);\nkernel/bpf/verifier.c-14732-\t\telse\n"
}

gemini-3.1-pro-preview

null

null

							input: 9673
							output: 41
							thoughts: 124
						

**Analyzing Potential FocusSymbols**

Okay, let's see. My initial assessment is that those functions: `scalar32_min_max_lsh`, `scalar_min_max_lsh`, `scalar32_min_max_rsh`, `scalar_min_max_rsh`, `scalar32_min_max_arsh`, `scalar_min_max_arsh`, are all strong contenders for inclusion in `FocusSymbols`. They seem like prime candidates. But, I should probably double check `is_safe_to_compute_dst_reg_range` before I go further. I want to be certain about this.

{
  "Expression": "is_safe_to_compute_dst_reg_range",
  "PathPrefix": "kernel/bpf/verifier.c"
}

{
  "Output": "kernel/bpf/verifier.c=14482=static void scalar_byte_swap(struct bpf_reg_state *dst_reg, struct bpf_insn *insn)\n--\nkernel/bpf/verifier.c-14530-\nkernel/bpf/verifier.c:14531:static bool is_safe_to_compute_dst_reg_range(struct bpf_insn *insn,\nkernel/bpf/verifier.c-14532-\t\t\t\t\t     const struct bpf_reg_state *src_reg)\n--\nkernel/bpf/verifier.c=14614=static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,\n--\nkernel/bpf/verifier.c-14623-\nkernel/bpf/verifier.c:14624:\tif (!is_safe_to_compute_dst_reg_range(insn, \u0026src_reg)) {\nkernel/bpf/verifier.c-14625-\t\t__mark_reg_unknown(env, dst_reg);\n"
}

gemini-3.1-pro-preview

null

null

							input: 10258
							output: 201
							thoughts: 376
						

**My Assessment of the Patch's Verifiability**

Okay, so `is_safe_to_compute_dst_reg_range` seems like another key function to consider, but let's first ensure we haven't missed any other config dependencies. Looking at the patch, the changes are centered in `kernel/bpf/verifier.c` and the associated selftests. The selftests are just validation checks, so they don't necessitate fuzzing. The heart of the matter lies squarely within `kernel/bpf/verifier.c`. Based on my understanding, `CONFIG_BPF_SYSCALL` is the only relevant configuration setting here.

Now, let's articulate the core reasoning for the fuzzing requirement. This patch fundamentally alters the BPF verifier to handle bounds tracking for shift operations (LSH, RSH, ARSH) where the shift *amount* isn't a constant, but a range. This introduces a significant functional change within a critical and frequently accessed part of the BPF verifier logic. Consequently, fuzzing is essential to detect potential vulnerabilities and ensure the accuracy of the new bounds tracking mechanism.

We need to focus on these symbols: `scalar32_min_max_lsh`, `scalar_min_max_lsh`, `scalar32_min_max_rsh`, `scalar_min_max_rsh`, `scalar32_min_max_arsh`, `scalar_min_max_arsh` and `is_safe_to_compute_dst_reg_range`.

Let's quickly check. Okay, `scalar32_min_max_lsh` is a static function. Now, are there any other functions impacted? Hmm, it looks like `__scalar32_min_max_lsh` wasn't modified, but `scalar32_min_max_lsh` was.

Alright, time to log the results.

{
  "EnableConfigs": [
    "BPF_SYSCALL"
  ],
  "FocusSymbols": [
    "scalar32_min_max_lsh",
    "scalar_min_max_lsh",
    "scalar32_min_max_rsh",
    "scalar_min_max_rsh",
    "scalar32_min_max_arsh",
    "scalar_min_max_arsh",
    "is_safe_to_compute_dst_reg_range"
  ],
  "Reasoning": "The patch modifies the BPF verifier to support tracking bounds for shift operations (LSH, RSH, ARSH) when the shift amount is not a constant, but a range. This is a functional change in the highly reachable and critical BPF verifier logic, which should be fuzzed to ensure it doesn't introduce any vulnerabilities or incorrect bounds tracking.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "BPF_SYSCALL"
  ],
  "FocusSymbols": [
    "scalar32_min_max_lsh",
    "scalar_min_max_lsh",
    "scalar32_min_max_rsh",
    "scalar_min_max_rsh",
    "scalar32_min_max_arsh",
    "scalar_min_max_arsh",
    "is_safe_to_compute_dst_reg_range"
  ],
  "Reasoning": "The patch modifies the BPF verifier to support tracking bounds for shift operations (LSH, RSH, ARSH) when the shift amount is not a constant, but a range. This is a functional change in the highly reachable and critical BPF verifier logic, which should be fuzzed to ensure it doesn't introduce any vulnerabilities or incorrect bounds tracking.",
  "WorthFuzzing": true
}