From 2b940bcde10c460c4e09570a31143f88c80c8c20 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Sun, 5 Oct 2025 18:20:37 -0700 Subject: [PATCH] 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: 4a1c9e544b8d ("libbpf: remove linux/unaligned.h dependency for libbpf_sha256()") Signed-off-by: Eric Biggers Signed-off-by: Andrii Nakryiko Acked-by: Yonghong Song Link: https://lore.kernel.org/bpf/20251006012037.159295-1-ebiggers@kernel.org --- src/libbpf_utils.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/src/libbpf_utils.c b/src/libbpf_utils.c index 5d66bc6..ac3beae 100644 --- a/src/libbpf_utils.c +++ b/src/libbpf_utils.c @@ -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 +static inline __u32 get_unaligned_be32(const void *p) +{ + __be32 val; -#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) + 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)))