Commit 4d920ed6 authored by Eric Biggers's avatar Eric Biggers Committed by Andrii Nakryiko
Browse files

libbpf: Fix undefined behavior in {get,put}_unaligned_be32() 



These violate aliasing rules and may be miscompiled unless
-fno-strict-aliasing is used.  Replace them with the standard memcpy()
solution.  Note that compilers know how to optimize this properly.

Fixes: 4a1c9e54 ("libbpf: remove linux/unaligned.h dependency for libbpf_sha256()")
Signed-off-by: default avatarEric Biggers <ebiggers@kernel.org>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarYonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/bpf/20251006012037.159295-1-ebiggers@kernel.org
parent de734222

tools/lib/bpf/libbpf_utils.c

+14 −10
Original line number Diff line number Diff line
@@ -148,16 +148,20 @@ const char *libbpf_errstr(int err) 
	}

}



#pragma GCC diagnostic push

#pragma GCC diagnostic ignored "-Wpacked"

#pragma GCC diagnostic ignored "-Wattributes"

struct __packed_u32 { __u32 __val; } __attribute__((packed));

#pragma GCC diagnostic pop



#define get_unaligned_be32(p) be32_to_cpu((((struct __packed_u32 *)(p))->__val))

#define put_unaligned_be32(v, p) do {							\

	((struct __packed_u32 *)(p))->__val = cpu_to_be32(v);				\

} while (0)

static inline __u32 get_unaligned_be32(const void *p)

{

	__be32 val;



	memcpy(&val, p, sizeof(val));

	return be32_to_cpu(val);

}



static inline void put_unaligned_be32(__u32 val, void *p)

{

	__be32 be_val = cpu_to_be32(val);



	memcpy(p, &be_val, sizeof(be_val));

}



#define SHA256_BLOCK_LENGTH 64

#define Ch(x, y, z) (((x) & (y)) ^ (~(x) & (z)))