Commit 088f35ab authored by Ankit Khushwaha's avatar Ankit Khushwaha Committed by Jakub Kicinski
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selftests/net/ipsec: Fix variable size type not at the end of struct 



The "struct alg" object contains a union of 3 xfrm structures:

	union {
		struct xfrm_algo;
		struct xfrm_algo_aead;
		struct xfrm_algo_auth;
	}

All of them end with a flexible array member used to store key material,
but the flexible array appears at *different offsets* in each struct.
bcz of this, union itself is of variable-sized & Placing it above
char buf[...] triggers:

ipsec.c:835:5: warning: field 'u' with variable sized type 'union
(unnamed union at ipsec.c:831:3)' not at the end of a struct or class
is a GNU extension [-Wgnu-variable-sized-type-not-at-end]
  835 |                 } u;
      |                   ^

one fix is to use "TRAILING_OVERLAP()" which works with one flexible
array member only.

But In "struct alg" flexible array member exists in all union members,
but not at the same offset, so TRAILING_OVERLAP cannot be applied.

so the fix is to explicitly overlay the key buffer at the correct offset
for the largest union member (xfrm_algo_auth). This ensures that the
flexible-array region and the fixed buffer line up.

No functional change.

Reviewed-by: default avatarSimon Horman <horms@kernel.org>
Signed-off-by: default avatarAnkit Khushwaha <ankitkhushwaha.linux@gmail.com>
Link: https://patch.msgid.link/20260109152201.15668-1-ankitkhushwaha.linux@gmail.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent e405b3c9

tools/testing/selftests/net/ipsec.c

+9 −2
Original line number Diff line number Diff line
@@ -43,6 +43,10 @@ 


#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))



#ifndef offsetof

#define offsetof(TYPE, MEMBER)	__builtin_offsetof(TYPE, MEMBER)

#endif



#define IPV4_STR_SZ	16	/* xxx.xxx.xxx.xxx is longest + \0 */

#define MAX_PAYLOAD	2048

#define XFRM_ALGO_KEY_BUF_SIZE	512
@@ -827,13 +831,16 @@ static int xfrm_fill_key(char *name, char *buf, 
static int xfrm_state_pack_algo(struct nlmsghdr *nh, size_t req_sz,

		struct xfrm_desc *desc)

{

	struct {

	union {

		union {

			struct xfrm_algo	alg;

			struct xfrm_algo_aead	aead;

			struct xfrm_algo_auth	auth;

		} u;

		struct {

			unsigned char __offset_to_FAM[offsetof(struct xfrm_algo_auth, alg_key)];

			char buf[XFRM_ALGO_KEY_BUF_SIZE];

		};

	} alg = {};

	size_t alen, elen, clen, aelen;

	unsigned short type;