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bpf: verifier: Accept dynptr mem as mem in helpers

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This allows using memory retrieved from dynptrs with helper functions
that accept ARG_PTR_TO_MEM. For instance, results from bpf_dynptr_data
can be passed along to bpf_strncmp.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
Link: https://lore.kernel.org/r/20230506013134.2492210-5-drosen@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Daniel Rosenberg 2023-05-05 18:31:33 -07:00 committed by Alexei Starovoitov
parent 3881fdfed2
commit 2012c867c8
1 changed files with 4 additions and 0 deletions
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4
kernel/bpf/verifier.c
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@ -7495,12 +7495,16 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
* ARG_PTR_TO_MEM + MAYBE_NULL is compatible with PTR_TO_MEM and PTR_TO_MEM + MAYBE_NULL, * ARG_PTR_TO_MEM + MAYBE_NULL is compatible with PTR_TO_MEM and PTR_TO_MEM + MAYBE_NULL,
* but ARG_PTR_TO_MEM is compatible only with PTR_TO_MEM but NOT with PTR_TO_MEM + MAYBE_NULL * but ARG_PTR_TO_MEM is compatible only with PTR_TO_MEM but NOT with PTR_TO_MEM + MAYBE_NULL
* *
* ARG_PTR_TO_MEM is compatible with PTR_TO_MEM that is tagged with a dynptr type.
*
* Therefore we fold these flags depending on the arg_type before comparison. * Therefore we fold these flags depending on the arg_type before comparison.
*/ */
if (arg_type & MEM_RDONLY) if (arg_type & MEM_RDONLY)
type &= ~MEM_RDONLY; type &= ~MEM_RDONLY;
if (arg_type & PTR_MAYBE_NULL) if (arg_type & PTR_MAYBE_NULL)
type &= ~PTR_MAYBE_NULL; type &= ~PTR_MAYBE_NULL;
if (base_type(arg_type) == ARG_PTR_TO_MEM)
type &= ~DYNPTR_TYPE_FLAG_MASK;
if (meta->func_id == BPF_FUNC_kptr_xchg && type & MEM_ALLOC) if (meta->func_id == BPF_FUNC_kptr_xchg && type & MEM_ALLOC)
type &= ~MEM_ALLOC; type &= ~MEM_ALLOC;