From a069190b590e108223cd841a1c2d0bfb92230ecc Mon Sep 17 00:00:00 2001 From: Puranjay Mohan Date: Fri, 2 Jan 2026 14:15:12 -0800 Subject: bpf: Replace __opt annotation with __nullable for kfuncs The __opt annotation was originally introduced specifically for buffer/size argument pairs in bpf_dynptr_slice() and bpf_dynptr_slice_rdwr(), allowing the buffer pointer to be NULL while still validating the size as a constant. The __nullable annotation serves the same purpose but is more general and is already used throughout the BPF subsystem for raw tracepoints, struct_ops, and other kfuncs. This patch unifies the two annotations by replacing __opt with __nullable. The key change is in the verifier's get_kfunc_ptr_arg_type() function, where mem/size pair detection is now performed before the nullable check. This ensures that buffer/size pairs are correctly classified as KF_ARG_PTR_TO_MEM_SIZE even when the buffer is nullable, while adding an !arg_mem_size condition to the nullable check prevents interference with mem/size pair handling. When processing KF_ARG_PTR_TO_MEM_SIZE arguments, the verifier now uses is_kfunc_arg_nullable() instead of the removed is_kfunc_arg_optional() to determine whether to skip size validation for NULL buffers. This is the first documentation added for the __nullable annotation, which has been in use since it was introduced but was previously undocumented. No functional changes to verifier behavior - nullable buffer/size pairs continue to work exactly as before. Acked-by: Eduard Zingerman Signed-off-by: Puranjay Mohan Link: https://lore.kernel.org/r/20260102221513.1961781-1-puranjay@kernel.org Signed-off-by: Alexei Starovoitov --- include/linux/bpf.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 4e9667ed6630..a63e47d2109c 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1434,7 +1434,7 @@ bool __bpf_dynptr_is_rdonly(const struct bpf_dynptr_kern *ptr); int __bpf_dynptr_write(const struct bpf_dynptr_kern *dst, u64 offset, void *src, u64 len, u64 flags); void *bpf_dynptr_slice_rdwr(const struct bpf_dynptr *p, u64 offset, - void *buffer__opt, u64 buffer__szk); + void *buffer__nullable, u64 buffer__szk); static inline int bpf_dynptr_check_off_len(const struct bpf_dynptr_kern *ptr, u64 offset, u64 len) { -- cgit v1.2.3