Augment selected Resource Lifetime Safety failures with structured diagnostics while preserving the existing verifier messages. Report unreleased references from check_reference_leak() using reference-scoped diagnostic history, and add state reports for dynptr, iterator, lock, and IRQ-flag lifetime misuse. IRQ restore mismatch and out-of-order diagnostics use IRQ context-scoped history when an IRQ-disabled region is active, so retained save/restore context is still visible after per-state history removal. Signed-off-by: Kumar Kartikeya Dwivedi --- kernel/bpf/diagnostics.c | 91 ++++++++++++++++++++++++++++++++++ kernel/bpf/diagnostics.h | 9 ++++ kernel/bpf/verifier.c | 103 ++++++++++++++++++++++++++++++++++++--- 3 files changed, 195 insertions(+), 8 deletions(-) diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c index 058574a1411e..5d20ea9e470e 100644 --- a/kernel/bpf/diagnostics.c +++ b/kernel/bpf/diagnostics.c @@ -18,6 +18,7 @@ #define REGISTER_TYPE_SAFETY "Register Type Safety" #define MEMORY_SAFETY "Memory Safety" +#define RESOURCE_LIFETIME_SAFETY "Resource Lifetime Safety" #define BPF_DIAG_TEXT_WIDTH 100 #define BPF_DIAG_TEXT_INDENT " " @@ -1735,6 +1736,96 @@ void bpf_diag_mem_bounds(struct bpf_verifier_env *env, u32 insn_idx, int regno, env, "Add or adjust a bounds check that proves offset + access_size stays within the object."); } +static const char *diag_lock_name(const struct bpf_reference_state *lock) +{ + switch (lock->type) { + case REF_TYPE_LOCK: + return "bpf_spin_lock"; + case REF_TYPE_RES_LOCK: + return "resource spin lock"; + case REF_TYPE_RES_LOCK_IRQ: + return "IRQ-saving resource spin lock"; + default: + return "lock"; + } +} + +static void diag_res_report(struct bpf_verifier_env *env, u32 insn_idx, const char *problem, + const char *reason) +{ + bpf_diag_header(env, RESOURCE_LIFETIME_SAFETY, problem); + diag_reason(env, "%s", reason); + + diag_section(env, "At"); + bpf_diag_source(env, insn_idx, "error", "%s", problem); +} + +void bpf_diag_res(struct bpf_verifier_env *env, u32 insn_idx, const char *problem, + const char *reason, const char *suggestion) +{ + diag_res_report(env, insn_idx, problem, reason); + diag_suggestion(env, "%s", suggestion); +} + +void bpf_diag_lock(struct bpf_verifier_env *env, u32 insn_idx, const char *problem, + const char *reason, const char *suggestion, + const struct bpf_reference_state *active_lock) +{ + diag_res_report(env, insn_idx, problem, reason); + + if (active_lock) { + diag_section(env, "Active lock"); + bpf_diag_source(env, active_lock->insn_idx, "acquired", + "active %s has verifier identity %d", + diag_lock_name(active_lock), active_lock->id); + } + + diag_suggestion(env, "%s", suggestion); +} + +void bpf_diag_irq(struct bpf_verifier_env *env, u32 insn_idx, const char *problem, + const char *reason, const char *suggestion, u32 depth) +{ + struct bpf_diag_history_opts opts = { + .scope = BPF_DIAG_HISTORY_SCOPE_CONTEXT, + .ctx_kind = BPF_DIAG_CONTEXT_IRQ, + .ctx_depth = depth, + }; + + bpf_diag_header(env, RESOURCE_LIFETIME_SAFETY, problem); + diag_reason(env, "%s", reason); + + diag_section(env, "At"); + bpf_diag_source(env, insn_idx, "error", "%s", problem); + + if (depth) + diag_print_history(env, &opts); + + diag_suggestion(env, "%s", suggestion); +} + +void bpf_diag_leak(struct bpf_verifier_env *env, u32 ref_id, u32 alloc_insn, u32 fail_insn) +{ + struct bpf_diag_history_opts opts = { + .scope = BPF_DIAG_HISTORY_SCOPE_REF, + .ref_id = ref_id, + }; + + bpf_diag_header(env, RESOURCE_LIFETIME_SAFETY, "unreleased resource"); + diag_reason( + env, "Owned resource (id=%u) was acquired at instruction %u and still needs to be released before this exit path.", + ref_id, alloc_insn); + + diag_section(env, "At"); + bpf_diag_source(env, fail_insn, "error", + "owned resource (id=%u) still needs release", ref_id); + + diag_print_history(env, &opts); + + diag_suggestion( + env, "Release or transfer ownership of the acquired resource on every path before the program exits."); +} + static const char *diag_var_offset(struct bpf_verifier_env *env, const struct bpf_diag_reg_snapshot *snapshot) { diff --git a/kernel/bpf/diagnostics.h b/kernel/bpf/diagnostics.h index b5feda71de3e..66dd2bb655b7 100644 --- a/kernel/bpf/diagnostics.h +++ b/kernel/bpf/diagnostics.h @@ -9,6 +9,7 @@ #include #include +struct bpf_reference_state; struct bpf_func_state; struct bpf_reg_state; struct bpf_verifier_env; @@ -68,6 +69,14 @@ void bpf_diag_memory(struct bpf_verifier_env *env, u32 insn_idx, const char *pro void bpf_diag_mem_bounds(struct bpf_verifier_env *env, u32 insn_idx, int regno, const char *reg_name, const char *type_name, const char *proof, int off, int size, u32 mem_size, const struct bpf_reg_state *reg); +void bpf_diag_res(struct bpf_verifier_env *env, u32 insn_idx, const char *problem, + const char *reason, const char *suggestion); +void bpf_diag_lock(struct bpf_verifier_env *env, u32 insn_idx, const char *problem, + const char *reason, const char *suggestion, + const struct bpf_reference_state *active_lock); +void bpf_diag_irq(struct bpf_verifier_env *env, u32 insn_idx, const char *problem, + const char *reason, const char *suggestion, u32 depth); +void bpf_diag_leak(struct bpf_verifier_env *env, u32 ref_id, u32 alloc_insn, u32 fail_insn); void bpf_diag_record_branch(struct bpf_verifier_env *env, u32 insn_idx, bool cond_true); void bpf_diag_mod_begin(struct bpf_verifier_env *env, const struct bpf_reg_state *reg, const struct bpf_reg_state *origin, enum bpf_diag_mod_reason reason); diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index cfc14167cad1..f5bf8cf644b8 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -816,6 +816,10 @@ static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env *env, if (dynptr_type_referenced(state->stack[spi].spilled_ptr.dynptr.type) && dynptr_ref_cnt(env, state->stack[spi].spilled_ptr.parent_id) <= 1) { verbose(env, "cannot overwrite referenced dynptr\n"); + bpf_diag_res( + env, env->insn_idx, "referenced dynptr overwrite", + "This stack slot contains a dynptr that owns or protects a referenced resource. Overwriting the last dynptr for that resource would lose the verifier-tracked release path.", + "Release or clone the dynptr so another live dynptr still tracks the referenced resource before overwriting this stack slot."); return -EINVAL; } @@ -1098,9 +1102,19 @@ static int unmark_stack_slot_irq_flag(struct bpf_verifier_env *env, struct bpf_r if (st->irq.kfunc_class != kfunc_class) { const char *flag_kfunc = st->irq.kfunc_class == IRQ_NATIVE_KFUNC ? "native" : "lock"; const char *used_kfunc = kfunc_class == IRQ_NATIVE_KFUNC ? "native" : "lock"; + const char *reason; verbose(env, "irq flag acquired by %s kfuncs cannot be restored with %s kfuncs\n", flag_kfunc, used_kfunc); + reason = bpf_diag_fmt(env, + "This IRQ flag was saved by %s IRQ kfuncs, but the restore call " + "belongs to the %s IRQ kfunc family. Save and restore operations " + "must use the same family.", + flag_kfunc, used_kfunc); + bpf_diag_irq(env, env->insn_idx, "IRQ flag restore mismatch", reason, + "Restore the flag with the matching IRQ restore kfunc for the save " + "operation that created it.", + bpf_diag_irq_depth(env->cur_state)); return -EINVAL; } @@ -1118,6 +1132,11 @@ static int unmark_stack_slot_irq_flag(struct bpf_verifier_env *env, struct bpf_r verbose(env, "cannot restore irq state out of order, expected id=%d acquired at insn_idx=%d\n", env->cur_state->active_irq_id, insn_idx); + bpf_diag_irq(env, env->insn_idx, "IRQ flag restore out of order", + "IRQ-disabled regions must be restored in last-in, first-out order, " + "but this restore does not match the currently active IRQ flag.", + "Restore nested IRQ flags in the reverse order they were saved.", + bpf_diag_irq_depth(env->cur_state)); return err; } @@ -7184,6 +7203,7 @@ static int process_spin_lock(struct bpf_verifier_env *env, struct bpf_reg_state bool is_lock = flags & PROCESS_SPIN_LOCK, is_res_lock = flags & PROCESS_RES_LOCK; const char *lock_str = is_res_lock ? "bpf_res_spin" : "bpf_spin"; struct bpf_verifier_state *cur = env->cur_state; + struct bpf_reference_state *lock; bool is_const = tnum_is_const(reg->var_off); bool is_irq = flags & PROCESS_LOCK_IRQ; u64 val = reg->var_off.value; @@ -7233,14 +7253,25 @@ static int process_spin_lock(struct bpf_verifier_env *env, struct bpf_reg_state ptr = btf; if (!is_res_lock && cur->active_locks) { - if (find_lock_state(env->cur_state, REF_TYPE_LOCK, 0, NULL)) { + lock = find_lock_state(cur, REF_TYPE_LOCK, 0, NULL); + if (lock) { verbose(env, "Locking two bpf_spin_locks are not allowed\n"); + bpf_diag_lock( + env, env->insn_idx, "nested spin lock", + "This path already holds a bpf_spin_lock. The verifier allows only one regular BPF spin lock at a time.", + "Unlock the current bpf_spin_lock before taking another one.", lock); return -EINVAL; } } else if (is_res_lock && cur->active_locks) { - if (find_lock_state(env->cur_state, REF_TYPE_RES_LOCK | REF_TYPE_RES_LOCK_IRQ, reg->id, ptr)) { + lock = find_lock_state(cur, REF_TYPE_RES_LOCK | REF_TYPE_RES_LOCK_IRQ, + reg->id, ptr); + if (lock) { verbose(env, "Acquiring the same lock again, AA deadlock detected\n"); + bpf_diag_lock( + env, env->insn_idx, "recursive resource spin lock", + "This path already holds the same resource spin lock. Taking it again would deadlock.", + "Avoid reacquiring the same resource spin lock before it is unlocked.", lock); return -EINVAL; } } @@ -7267,6 +7298,10 @@ static int process_spin_lock(struct bpf_verifier_env *env, struct bpf_reg_state if (!cur->active_locks) { verbose(env, "%s_unlock without taking a lock\n", lock_str); + bpf_diag_res( + env, env->insn_idx, "unlock without lock", + "This unlock operation has no matching active lock on the current path.", + "Take the matching lock before this unlock, or remove the unmatched unlock path."); return -EINVAL; } @@ -7276,16 +7311,35 @@ static int process_spin_lock(struct bpf_verifier_env *env, struct bpf_reg_state type = REF_TYPE_RES_LOCK; else type = REF_TYPE_LOCK; - if (!find_lock_state(cur, type, reg->id, ptr)) { + + lock = find_lock_state(cur, type, reg->id, ptr); + if (!lock) { verbose(env, "%s_unlock of different lock\n", lock_str); + lock = find_lock_state(cur, REF_TYPE_LOCK_MASK, cur->active_lock_id, + cur->active_lock_ptr); + bpf_diag_lock( + env, env->insn_idx, "unlock of a different lock", + "This unlock does not match any active lock with the same tracked identity on the current path.", + "Unlock the same lock object that was most recently acquired.", lock); return -EINVAL; } if (reg->id != cur->active_lock_id || ptr != cur->active_lock_ptr) { verbose(env, "%s_unlock cannot be out of order\n", lock_str); + lock = find_lock_state(cur, REF_TYPE_LOCK_MASK, cur->active_lock_id, + cur->active_lock_ptr); + bpf_diag_lock( + env, env->insn_idx, "unlock out of order", + "Locks must be released in last-in, first-out order, but this unlock does not match the currently active lock.", + "Release nested locks in the reverse order they were acquired.", lock); return -EINVAL; } if (release_lock_state(env, type, reg->id, ptr)) { verbose(env, "%s_unlock of different lock\n", lock_str); + bpf_diag_lock( + env, env->insn_idx, "unlock of a different lock", + "The verifier could not release a lock state matching this unlock operation.", + "Pass the same lock object and lock kind that were used for the matching lock operation.", + lock); return -EINVAL; } if (!in_rcu_cs(env)) @@ -7463,6 +7517,10 @@ static int process_dynptr_func(struct bpf_verifier_env *env, struct bpf_reg_stat if (!is_dynptr_reg_valid_uninit(env, reg)) { verbose(env, "Dynptr has to be an uninitialized dynptr\n"); + bpf_diag_res( + env, insn_idx, "dynptr is already initialized", + "This kfunc constructs a dynptr and requires an uninitialized dynptr stack slot, but the selected slot already holds dynptr state.", + "Use a fresh stack dynptr slot, or release/destroy the existing dynptr before reusing the slot."); return -EINVAL; } @@ -7479,21 +7537,29 @@ static int process_dynptr_func(struct bpf_verifier_env *env, struct bpf_reg_stat /* For the reg->type == PTR_TO_STACK case, bpf_dynptr is never const */ if (reg->type == CONST_PTR_TO_DYNPTR && (arg_type & OBJ_RELEASE)) { verbose(env, "CONST_PTR_TO_DYNPTR cannot be released\n"); + bpf_diag_res( + env, insn_idx, "const dynptr release", + "This release operation was given a const dynptr. Const dynptr values are verifier-provided views and cannot be released by the program.", + "Release only mutable dynptrs that the program initialized or reserved."); return -EINVAL; } if (!is_dynptr_reg_valid_init(env, reg)) { verbose(env, "Expected an initialized dynptr as %s\n", reg_arg_name(env, argno)); + bpf_diag_res( + env, insn_idx, "uninitialized dynptr use", + "This operation requires an initialized dynptr, but the stack slot does not currently hold a valid dynptr on this path.", + "Initialize the dynptr on every path before this call, and avoid overwriting or releasing it before this use."); return -EINVAL; } /* Fold modifiers (in this case, OBJ_RELEASE) when checking expected type */ if (!is_dynptr_type_expected(env, reg, arg_type & ~OBJ_RELEASE)) { - verbose(env, - "Expected a dynptr of type %s as %s\n", - dynptr_type_str(arg_to_dynptr_type(arg_type)), - reg_arg_name(env, argno)); + enum bpf_dynptr_type expected_type = arg_to_dynptr_type(arg_type); + + verbose(env, "Expected a dynptr of type %s as %s\n", + dynptr_type_str(expected_type), reg_arg_name(env, argno)); return -EINVAL; } @@ -7580,6 +7646,10 @@ static int process_iter_arg(struct bpf_verifier_env *env, struct bpf_reg_state * if (!is_iter_reg_valid_uninit(env, reg, nr_slots)) { verbose(env, "expected uninitialized iter_%s as %s\n", iter_type_str(meta->btf, btf_id), reg_arg_name(env, argno)); + bpf_diag_res( + env, insn_idx, "iterator is already initialized", + "Iterator creation requires an uninitialized iterator stack object, but this stack range already contains iterator state.", + "Use a fresh iterator stack slot, or destroy the existing iterator before reusing the slot."); return -EINVAL; } @@ -7604,6 +7674,10 @@ static int process_iter_arg(struct bpf_verifier_env *env, struct bpf_reg_state * case -EINVAL: verbose(env, "expected an initialized iter_%s as %s\n", iter_type_str(meta->btf, btf_id), reg_arg_name(env, argno)); + bpf_diag_res( + env, insn_idx, "uninitialized iterator use", + "This iterator operation requires an initialized iterator state object, but the stack range does not contain a live iterator on this path.", + "Call the matching iterator new kfunc on every path before calling next or destroy, and do not destroy the iterator before this use."); return err; case -EPROTO: verbose(env, "expected an RCU CS when using %s\n", meta->func_name); @@ -9476,7 +9550,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog, if (ret) return ret; - ret = process_dynptr_func(env, reg, argno, -1, arg->arg_type, &ref_obj, NULL); + ret = process_dynptr_func(env, reg, argno, env->insn_idx, arg->arg_type, + &ref_obj, NULL); if (ret) return ret; } else if (base_type(arg->arg_type) == ARG_PTR_TO_BTF_ID) { @@ -10274,6 +10349,7 @@ static int check_reference_leak(struct bpf_verifier_env *env, bool exception_exi continue; verbose(env, "Unreleased reference id=%d alloc_insn=%d\n", state->refs[i].id, state->refs[i].insn_idx); + bpf_diag_leak(env, state->refs[i].id, state->refs[i].insn_idx, env->insn_idx); refs_lingering = true; } return refs_lingering ? -EINVAL : 0; @@ -11824,6 +11900,12 @@ static int process_irq_flag(struct bpf_verifier_env *env, struct bpf_reg_state * if (!is_irq_flag_reg_valid_uninit(env, reg)) { verbose(env, "expected uninitialized irq flag as %s\n", reg_arg_name(env, argno)); + bpf_diag_res(env, env->insn_idx, "IRQ flag is already initialized", + "Saving IRQ state requires an uninitialized stack slot for " + "the IRQ flag, but this slot already contains tracked IRQ " + "flag state.", + "Use a fresh stack slot for this save operation, or restore " + "the existing IRQ flag before reusing the slot."); return -EINVAL; } @@ -11840,6 +11922,11 @@ static int process_irq_flag(struct bpf_verifier_env *env, struct bpf_reg_state * if (err) { verbose(env, "expected an initialized irq flag as %s\n", reg_arg_name(env, argno)); + bpf_diag_res(env, env->insn_idx, "uninitialized IRQ flag restore", + "Restoring IRQ state requires a stack slot that was " + "initialized by a matching IRQ save operation on this path.", + "Pass the same stack slot that was previously initialized by " + "the matching IRQ save kfunc."); return err; } -- 2.53.0