On Tue, 2026-01-20 at 16:28 +0800, Zesen Liu wrote:
> After commit 37cce22dbd51 ("bpf: verifier: Refactor helper access type
> tracking"),
> the verifier started relying on the access type flags in helper
> function prototypes to perform memory access optimizations.
>
> Currently, several helper functions utilizing ARG_PTR_TO_MEM lack the
> corresponding MEM_RDONLY or MEM_WRITE flags. This omission causes the
> verifier to incorrectly assume that the buffer contents are unchanged
> across the helper call. Consequently, the verifier may optimize away
> subsequent reads based on this wrong assumption, leading to correctness
> issues.
>
> For bpf_get_stack_proto_raw_tp, the original MEM_RDONLY was incorrect
> since the helper writes to the buffer. Change it to ARG_PTR_TO_UNINIT_MEM
> which correctly indicates write access to potentially uninitialized memory.
>
> Similar issues were recently addressed for specific helpers in commit
> ac44dcc788b9 ("bpf: Fix verifier assumptions of bpf_d_path's output buffer")
> and commit 2eb7648558a7 ("bpf: Specify access type of bpf_sysctl_get_name
> args").
>
> Fix these prototypes by adding the correct memory access flags.
>
> Fixes: 37cce22dbd51 ("bpf: verifier: Refactor helper access type tracking")
> Co-developed-by: Shuran Liu <[email protected]>
> Signed-off-by: Shuran Liu <[email protected]>
> Co-developed-by: Peili Gao <[email protected]>
> Signed-off-by: Peili Gao <[email protected]>
> Co-developed-by: Haoran Ni <[email protected]>
> Signed-off-by: Haoran Ni <[email protected]>
> Signed-off-by: Zesen Liu <[email protected]>
> ---
Acked-by: Eduard Zingerman <[email protected]>
