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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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db243b7964
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>
96 lines
2.5 KiB
C
96 lines
2.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef NET_COMPAT_H
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#define NET_COMPAT_H
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struct sock;
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#include <linux/compat.h>
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struct compat_msghdr {
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compat_uptr_t msg_name; /* void * */
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compat_int_t msg_namelen;
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compat_uptr_t msg_iov; /* struct compat_iovec * */
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compat_size_t msg_iovlen;
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compat_uptr_t msg_control; /* void * */
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compat_size_t msg_controllen;
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compat_uint_t msg_flags;
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};
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struct compat_mmsghdr {
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struct compat_msghdr msg_hdr;
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compat_uint_t msg_len;
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};
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struct compat_cmsghdr {
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compat_size_t cmsg_len;
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compat_int_t cmsg_level;
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compat_int_t cmsg_type;
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};
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struct compat_rtentry {
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u32 rt_pad1;
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struct sockaddr rt_dst; /* target address */
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struct sockaddr rt_gateway; /* gateway addr (RTF_GATEWAY) */
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struct sockaddr rt_genmask; /* target network mask (IP) */
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unsigned short rt_flags;
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short rt_pad2;
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u32 rt_pad3;
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unsigned char rt_tos;
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unsigned char rt_class;
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short rt_pad4;
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short rt_metric; /* +1 for binary compatibility! */
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compat_uptr_t rt_dev; /* forcing the device at add */
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u32 rt_mtu; /* per route MTU/Window */
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u32 rt_window; /* Window clamping */
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unsigned short rt_irtt; /* Initial RTT */
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};
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int __get_compat_msghdr(struct msghdr *kmsg, struct compat_msghdr __user *umsg,
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struct sockaddr __user **save_addr, compat_uptr_t *ptr,
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compat_size_t *len);
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int get_compat_msghdr(struct msghdr *, struct compat_msghdr __user *,
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struct sockaddr __user **, struct iovec **);
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int put_cmsg_compat(struct msghdr*, int, int, int, void *);
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int cmsghdr_from_user_compat_to_kern(struct msghdr *, struct sock *,
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unsigned char *, int);
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struct compat_group_req {
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__u32 gr_interface;
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struct __kernel_sockaddr_storage gr_group
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__aligned(4);
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} __packed;
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struct compat_group_source_req {
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__u32 gsr_interface;
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struct __kernel_sockaddr_storage gsr_group
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__aligned(4);
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struct __kernel_sockaddr_storage gsr_source
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__aligned(4);
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} __packed;
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struct compat_group_filter {
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union {
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struct {
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__u32 gf_interface_aux;
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struct __kernel_sockaddr_storage gf_group_aux
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__aligned(4);
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__u32 gf_fmode_aux;
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__u32 gf_numsrc_aux;
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struct __kernel_sockaddr_storage gf_slist[1]
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__aligned(4);
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} __packed;
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struct {
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__u32 gf_interface;
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struct __kernel_sockaddr_storage gf_group
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__aligned(4);
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__u32 gf_fmode;
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__u32 gf_numsrc;
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struct __kernel_sockaddr_storage gf_slist_flex[]
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__aligned(4);
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} __packed;
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};
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} __packed;
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#endif /* NET_COMPAT_H */
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