In check_alu_op(), the verifier currently calls check_reg_arg() and adjust_scalar_min_max_vals() unconditionally for BPF_NEG operations. However, if the destination register holds a pointer, these scalar adjustments are unnecessary and potentially incorrect. This patch adds a check to skip the adjustment logic when the destination register contains a pointer. Reported-by: syzbot+d36d5ae81e1b0a53ef58@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=d36d5ae81e1b0a53ef58 Fixes: aced132599b3 ("bpf: Add range tracking for BPF_NEG") Suggested-by: KaFai Wan Suggested-by: Eduard Zingerman Signed-off-by: Brahmajit Das --- Changes v4: Cleaning up, instead of using __is_pointer_value it's further simplified by checking if regs[insn->dst_reg].type of SCALAR_VALUE Link: Changes in v3: using __is_pointer_value to check if register if of pointer type Link: https://lore.kernel.org/all/20251001095613.267475-1-listout@listout.xyz/ Changes in v2: Checking if reg->map_ptr is NULL in bpf/log.c but with cleaner approach (wrong approach) Link: https://lore.kernel.org/all/20250923174738.1713751-1-listout@listout.xyz/ Changes in v1: Checking if reg->map_ptr is NULL in bpf/log.c (wrong approach) Link: https://lore.kernel.org/all/20250923164144.1573636-1-listout@listout.xyz/ --- kernel/bpf/verifier.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index e892df386eed..f3d8ba142faa 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -15645,7 +15645,8 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn) } /* check dest operand */ - if (opcode == BPF_NEG) { + if (opcode == BPF_NEG && + regs[insn->dst_reg].type == SCALAR_VALUE) { err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK); err = err ?: adjust_scalar_min_max_vals(env, insn, ®s[insn->dst_reg], -- 2.51.0