Commit 2012c867 authored by Daniel Rosenberg's avatar Daniel Rosenberg Committed by Alexei Starovoitov
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bpf: verifier: Accept dynptr mem as mem in helpers 



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: default avatarDaniel Rosenberg <drosen@google.com>
Link: https://lore.kernel.org/r/20230506013134.2492210-5-drosen@google.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 3881fdfe

kernel/bpf/verifier.c

+4 −0
Original line number Diff line number Diff line
@@ -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,

	 * 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.

	 */

	if (arg_type & MEM_RDONLY)

		type &= ~MEM_RDONLY;

	if (arg_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)









		type &= ~MEM_ALLOC;