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authorGustavo A. R. Silva <gustavoars@kernel.org>2021-08-04 23:45:36 +0300
committerDavid S. Miller <davem@davemloft.net>2021-08-05 13:46:42 +0300
commitdb243b796439c0caba47865564d8acd18a301d18 (patch)
tree4d9286e7e1146337ff111a5cf0b2552dc9cc5195 /include/net/compat.h
parentd15040a33883c3ab2ee2ea17e6427ce24e9f3ac0 (diff)
downloadlinux-db243b796439c0caba47865564d8acd18a301d18.tar.xz
net/ipv4/ipv6: Replace one-element arraya with flexible-array members
There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2]. Use an anonymous union with a couple of anonymous structs in order to keep userspace unchanged and refactor the related code accordingly: $ pahole -C group_filter net/ipv4/ip_sockglue.o struct group_filter { union { struct { __u32 gf_interface_aux; /* 0 4 */ /* XXX 4 bytes hole, try to pack */ struct __kernel_sockaddr_storage gf_group_aux; /* 8 128 */ /* --- cacheline 2 boundary (128 bytes) was 8 bytes ago --- */ __u32 gf_fmode_aux; /* 136 4 */ __u32 gf_numsrc_aux; /* 140 4 */ struct __kernel_sockaddr_storage gf_slist[1]; /* 144 128 */ }; /* 0 272 */ struct { __u32 gf_interface; /* 0 4 */ /* XXX 4 bytes hole, try to pack */ struct __kernel_sockaddr_storage gf_group; /* 8 128 */ /* --- cacheline 2 boundary (128 bytes) was 8 bytes ago --- */ __u32 gf_fmode; /* 136 4 */ __u32 gf_numsrc; /* 140 4 */ struct __kernel_sockaddr_storage gf_slist_flex[0]; /* 144 0 */ }; /* 0 144 */ }; /* 0 272 */ /* size: 272, cachelines: 5, members: 1 */ /* last cacheline: 16 bytes */ }; $ pahole -C compat_group_filter net/ipv4/ip_sockglue.o struct compat_group_filter { union { struct { __u32 gf_interface_aux; /* 0 4 */ struct __kernel_sockaddr_storage gf_group_aux __attribute__((__aligned__(4))); /* 4 128 */ /* --- cacheline 2 boundary (128 bytes) was 4 bytes ago --- */ __u32 gf_fmode_aux; /* 132 4 */ __u32 gf_numsrc_aux; /* 136 4 */ struct __kernel_sockaddr_storage gf_slist[1] __attribute__((__aligned__(4))); /* 140 128 */ } __attribute__((__packed__)) __attribute__((__aligned__(4))); /* 0 268 */ struct { __u32 gf_interface; /* 0 4 */ struct __kernel_sockaddr_storage gf_group __attribute__((__aligned__(4))); /* 4 128 */ /* --- cacheline 2 boundary (128 bytes) was 4 bytes ago --- */ __u32 gf_fmode; /* 132 4 */ __u32 gf_numsrc; /* 136 4 */ struct __kernel_sockaddr_storage gf_slist_flex[0] __attribute__((__aligned__(4))); /* 140 0 */ } __attribute__((__packed__)) __attribute__((__aligned__(4))); /* 0 140 */ } __attribute__((__aligned__(1))); /* 0 268 */ /* size: 268, cachelines: 5, members: 1 */ /* forced alignments: 1 */ /* last cacheline: 12 bytes */ } __attribute__((__packed__)); This helps with the ongoing efforts to globally enable -Warray-bounds and get us closer to being able to tighten the FORTIFY_SOURCE routines on memcpy(). [1] https://en.wikipedia.org/wiki/Flexible_array_member [2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays Link: https://github.com/KSPP/linux/issues/79 Link: https://github.com/KSPP/linux/issues/109 Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/compat.h')
-rw-r--r--include/net/compat.h27
1 files changed, 20 insertions, 7 deletions
diff --git a/include/net/compat.h b/include/net/compat.h
index 84805bdc4435..595fee069b82 100644
--- a/include/net/compat.h
+++ b/include/net/compat.h
@@ -71,13 +71,26 @@ struct compat_group_source_req {
} __packed;
struct compat_group_filter {
- __u32 gf_interface;
- struct __kernel_sockaddr_storage gf_group
- __aligned(4);
- __u32 gf_fmode;
- __u32 gf_numsrc;
- struct __kernel_sockaddr_storage gf_slist[1]
- __aligned(4);
+ union {
+ struct {
+ __u32 gf_interface_aux;
+ struct __kernel_sockaddr_storage gf_group_aux
+ __aligned(4);
+ __u32 gf_fmode_aux;
+ __u32 gf_numsrc_aux;
+ struct __kernel_sockaddr_storage gf_slist[1]
+ __aligned(4);
+ } __packed;
+ struct {
+ __u32 gf_interface;
+ struct __kernel_sockaddr_storage gf_group
+ __aligned(4);
+ __u32 gf_fmode;
+ __u32 gf_numsrc;
+ struct __kernel_sockaddr_storage gf_slist_flex[]
+ __aligned(4);
+ } __packed;
+ };
} __packed;
#endif /* NET_COMPAT_H */