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authorQian Cai <cai@lca.pw>2019-07-30 11:30:33 -0400
committerDavid S. Miller <davem@davemloft.net>2019-08-03 11:02:46 -0700
commit5e5412c365a32e452daa762eac36121cb8a370bb (patch)
tree855156e17fbe0b130f12916195d0e266d1eb4f3f
parent59c0b47a1e11b5e81ab1dfd13579c9fbdb02f0b4 (diff)
net/socket: fix GCC8+ Wpacked-not-aligned warnings
There are a lot of those warnings with GCC8+ 64-bit, In file included from ./include/linux/sctp.h:42, from net/core/skbuff.c:47: ./include/uapi/linux/sctp.h:395:1: warning: alignment 4 of 'struct sctp_paddr_change' is less than 8 [-Wpacked-not-aligned] } __attribute__((packed, aligned(4))); ^ ./include/uapi/linux/sctp.h:728:1: warning: alignment 4 of 'struct sctp_setpeerprim' is less than 8 [-Wpacked-not-aligned] } __attribute__((packed, aligned(4))); ^ ./include/uapi/linux/sctp.h:727:26: warning: 'sspp_addr' offset 4 in 'struct sctp_setpeerprim' isn't aligned to 8 [-Wpacked-not-aligned] struct sockaddr_storage sspp_addr; ^~~~~~~~~ ./include/uapi/linux/sctp.h:741:1: warning: alignment 4 of 'struct sctp_prim' is less than 8 [-Wpacked-not-aligned] } __attribute__((packed, aligned(4))); ^ ./include/uapi/linux/sctp.h:740:26: warning: 'ssp_addr' offset 4 in 'struct sctp_prim' isn't aligned to 8 [-Wpacked-not-aligned] struct sockaddr_storage ssp_addr; ^~~~~~~~ ./include/uapi/linux/sctp.h:792:1: warning: alignment 4 of 'struct sctp_paddrparams' is less than 8 [-Wpacked-not-aligned] } __attribute__((packed, aligned(4))); ^ ./include/uapi/linux/sctp.h:784:26: warning: 'spp_address' offset 4 in 'struct sctp_paddrparams' isn't aligned to 8 [-Wpacked-not-aligned] struct sockaddr_storage spp_address; ^~~~~~~~~~~ ./include/uapi/linux/sctp.h:905:1: warning: alignment 4 of 'struct sctp_paddrinfo' is less than 8 [-Wpacked-not-aligned] } __attribute__((packed, aligned(4))); ^ ./include/uapi/linux/sctp.h:899:26: warning: 'spinfo_address' offset 4 in 'struct sctp_paddrinfo' isn't aligned to 8 [-Wpacked-not-aligned] struct sockaddr_storage spinfo_address; ^~~~~~~~~~~~~~ This is because the commit 20c9c825b12f ("[SCTP] Fix SCTP socket options to work with 32-bit apps on 64-bit kernels.") added "packed, aligned(4)" GCC attributes to some structures but one of the members, i.e, "struct sockaddr_storage" in those structures has the attribute, "aligned(__alignof__ (struct sockaddr *)" which is 8-byte on 64-bit systems, so the commit overwrites the designed alignments for "sockaddr_storage". To fix this, "struct sockaddr_storage" needs to be aligned to 4-byte as it is only used in those packed sctp structure which is part of UAPI, and "struct __kernel_sockaddr_storage" is used in some other places of UAPI that need not to change alignments in order to not breaking userspace. Use an implicit alignment for "struct __kernel_sockaddr_storage" so it can keep the same alignments as a member in both packed and un-packed structures without breaking UAPI. Suggested-by: David Laight <David.Laight@ACULAB.COM> Signed-off-by: Qian Cai <cai@lca.pw> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--include/uapi/linux/socket.h19
1 files changed, 13 insertions, 6 deletions
diff --git a/include/uapi/linux/socket.h b/include/uapi/linux/socket.h
index 8eb96021709c..c3409c8ec0dd 100644
--- a/include/uapi/linux/socket.h
+++ b/include/uapi/linux/socket.h
@@ -6,17 +6,24 @@
* Desired design of maximum size and alignment (see RFC2553)
*/
#define _K_SS_MAXSIZE 128 /* Implementation specific max size */
-#define _K_SS_ALIGNSIZE (__alignof__ (struct sockaddr *))
- /* Implementation specific desired alignment */
typedef unsigned short __kernel_sa_family_t;
+/*
+ * The definition uses anonymous union and struct in order to control the
+ * default alignment.
+ */
struct __kernel_sockaddr_storage {
- __kernel_sa_family_t ss_family; /* address family */
- /* Following field(s) are implementation specific */
- char __data[_K_SS_MAXSIZE - sizeof(unsigned short)];
+ union {
+ struct {
+ __kernel_sa_family_t ss_family; /* address family */
+ /* Following field(s) are implementation specific */
+ char __data[_K_SS_MAXSIZE - sizeof(unsigned short)];
/* space to achieve desired size, */
/* _SS_MAXSIZE value minus size of ss_family */
-} __attribute__ ((aligned(_K_SS_ALIGNSIZE))); /* force desired alignment */
+ };
+ void *__align; /* implementation specific desired alignment */
+ };
+};
#endif /* _UAPI_LINUX_SOCKET_H */