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| author | Kumar Kartikeya Dwivedi <memxor@gmail.com> | 2022-11-03 22:09:53 +0300 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2022-11-04 05:31:18 +0300 |
| commit | f5e477a861e4a20d8a1c5f7a245f3a3c3c376b03 (patch) | |
| tree | 8f00e791553646a25e3e744566593ce18896d70c /kernel | |
| parent | 261f4664caffdeb9dff4e83ee3c0334b1c3a552f (diff) | |
| download | linux-f5e477a861e4a20d8a1c5f7a245f3a3c3c376b03.tar.xz | |
bpf: Fix slot type check in check_stack_write_var_off
For the case where allow_ptr_leaks is false, code is checking whether
slot type is STACK_INVALID and STACK_SPILL and rejecting other cases.
This is a consequence of incorrectly checking for register type instead
of the slot type (NOT_INIT and SCALAR_VALUE respectively). Fix the
check.
Fixes: 01f810ace9ed ("bpf: Allow variable-offset stack access")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221103191013.1236066-5-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/verifier.c | 19 |
1 files changed, 11 insertions, 8 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 7bf12c492201..eb111a8034e7 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3181,14 +3181,17 @@ static int check_stack_write_var_off(struct bpf_verifier_env *env, stype = &state->stack[spi].slot_type[slot % BPF_REG_SIZE]; mark_stack_slot_scratched(env, spi); - if (!env->allow_ptr_leaks - && *stype != NOT_INIT - && *stype != SCALAR_VALUE) { - /* Reject the write if there's are spilled pointers in - * range. If we didn't reject here, the ptr status - * would be erased below (even though not all slots are - * actually overwritten), possibly opening the door to - * leaks. + if (!env->allow_ptr_leaks && *stype != STACK_MISC && *stype != STACK_ZERO) { + /* Reject the write if range we may write to has not + * been initialized beforehand. If we didn't reject + * here, the ptr status would be erased below (even + * though not all slots are actually overwritten), + * possibly opening the door to leaks. + * + * We do however catch STACK_INVALID case below, and + * only allow reading possibly uninitialized memory + * later for CAP_PERFMON, as the write may not happen to + * that slot. */ verbose(env, "spilled ptr in range of var-offset stack write; insn %d, ptr off: %d", insn_idx, i); |