diff options
| author | Kumar Kartikeya Dwivedi <memxor@gmail.com> | 2024-12-03 20:47:53 -0800 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2024-12-04 09:19:50 -0800 |
| commit | 69772f509e084ec6bca12dbcdeeeff41b0103774 (patch) | |
| tree | fb7e9f2a3a07c229721e49998ede2df525468b06 /kernel | |
| parent | 5a6ea7022ff4d2a65ae328619c586d6a8909b48b (diff) | |
bpf: Don't mark STACK_INVALID as STACK_MISC in mark_stack_slot_misc
Inside mark_stack_slot_misc, we should not upgrade STACK_INVALID to
STACK_MISC when allow_ptr_leaks is false, since invalid contents
shouldn't be read unless the program has the relevant capabilities.
The relaxation only makes sense when env->allow_ptr_leaks is true.
However, such conversion in privileged mode becomes unnecessary, as
invalid slots can be read without being upgraded to STACK_MISC.
Currently, the condition is inverted (i.e. checking for true instead of
false), simply remove it to restore correct behavior.
Fixes: eaf18febd6eb ("bpf: preserve STACK_ZERO slots on partial reg spills")
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Reported-by: Tao Lyu <tao.lyu@epfl.ch>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20241204044757.1483141-2-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/verifier.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 2fd35465d650..f18aad339de8 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1202,14 +1202,17 @@ static bool is_spilled_scalar_reg64(const struct bpf_stack_state *stack) /* Mark stack slot as STACK_MISC, unless it is already STACK_INVALID, in which * case they are equivalent, or it's STACK_ZERO, in which case we preserve * more precise STACK_ZERO. - * Note, in uprivileged mode leaving STACK_INVALID is wrong, so we take - * env->allow_ptr_leaks into account and force STACK_MISC, if necessary. + * Regardless of allow_ptr_leaks setting (i.e., privileged or unprivileged + * mode), we won't promote STACK_INVALID to STACK_MISC. In privileged case it is + * unnecessary as both are considered equivalent when loading data and pruning, + * in case of unprivileged mode it will be incorrect to allow reads of invalid + * slots. */ static void mark_stack_slot_misc(struct bpf_verifier_env *env, u8 *stype) { if (*stype == STACK_ZERO) return; - if (env->allow_ptr_leaks && *stype == STACK_INVALID) + if (*stype == STACK_INVALID) return; *stype = STACK_MISC; } |