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>
This commit is contained in:
Gustavo A. R. Silva
David S. Miller
parent
d15040a338
commit
db243b7964
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@ -71,13 +71,26 @@ struct compat_group_source_req {
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} __packed;
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struct compat_group_filter {
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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[1]
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__aligned(4);
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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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@ -222,11 +222,22 @@ struct group_source_req {
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};
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struct group_filter {
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__u32 gf_interface; /* interface index */
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struct __kernel_sockaddr_storage gf_group; /* multicast address */
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__u32 gf_fmode; /* filter mode */
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__u32 gf_numsrc; /* number of sources */
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struct __kernel_sockaddr_storage gf_slist[1]; /* interface index */
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union {
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struct {
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__u32 gf_interface_aux; /* interface index */
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struct __kernel_sockaddr_storage gf_group_aux; /* multicast address */
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__u32 gf_fmode_aux; /* filter mode */
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__u32 gf_numsrc_aux; /* number of sources */
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struct __kernel_sockaddr_storage gf_slist[1]; /* interface index */
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};
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struct {
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__u32 gf_interface; /* interface index */
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struct __kernel_sockaddr_storage gf_group; /* multicast address */
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__u32 gf_fmode; /* filter mode */
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__u32 gf_numsrc; /* number of sources */
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struct __kernel_sockaddr_storage gf_slist_flex[]; /* interface index */
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};
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};
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};
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#define GROUP_FILTER_SIZE(numsrc) \
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@ -790,7 +790,8 @@ static int ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval, int optlen)
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goto out_free_gsf;
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err = set_mcast_msfilter(sk, gsf->gf_interface, gsf->gf_numsrc,
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gsf->gf_fmode, &gsf->gf_group, gsf->gf_slist);
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gsf->gf_fmode, &gsf->gf_group,
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gsf->gf_slist_flex);
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out_free_gsf:
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kfree(gsf);
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return err;
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@ -799,7 +800,7 @@ out_free_gsf:
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static int compat_ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
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int optlen)
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{
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const int size0 = offsetof(struct compat_group_filter, gf_slist);
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const int size0 = offsetof(struct compat_group_filter, gf_slist_flex);
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struct compat_group_filter *gf32;
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unsigned int n;
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void *p;
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@ -813,7 +814,7 @@ static int compat_ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
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p = kmalloc(optlen + 4, GFP_KERNEL);
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if (!p)
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return -ENOMEM;
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gf32 = p + 4; /* we want ->gf_group and ->gf_slist aligned */
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gf32 = p + 4; /* we want ->gf_group and ->gf_slist_flex aligned */
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err = -EFAULT;
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if (copy_from_sockptr(gf32, optval, optlen))
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@ -826,7 +827,7 @@ static int compat_ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
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goto out_free_gsf;
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err = -EINVAL;
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if (offsetof(struct compat_group_filter, gf_slist[n]) > optlen)
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if (offsetof(struct compat_group_filter, gf_slist_flex[n]) > optlen)
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goto out_free_gsf;
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/* numsrc >= (4G-140)/128 overflow in 32 bits */
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@ -834,7 +835,7 @@ static int compat_ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
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if (n > sock_net(sk)->ipv4.sysctl_igmp_max_msf)
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goto out_free_gsf;
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err = set_mcast_msfilter(sk, gf32->gf_interface, n, gf32->gf_fmode,
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&gf32->gf_group, gf32->gf_slist);
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&gf32->gf_group, gf32->gf_slist_flex);
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out_free_gsf:
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kfree(p);
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return err;
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@ -1455,7 +1456,7 @@ static bool getsockopt_needs_rtnl(int optname)
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static int ip_get_mcast_msfilter(struct sock *sk, void __user *optval,
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int __user *optlen, int len)
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{
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const int size0 = offsetof(struct group_filter, gf_slist);
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const int size0 = offsetof(struct group_filter, gf_slist_flex);
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struct group_filter __user *p = optval;
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struct group_filter gsf;
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int num;
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@ -1467,7 +1468,7 @@ static int ip_get_mcast_msfilter(struct sock *sk, void __user *optval,
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return -EFAULT;
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num = gsf.gf_numsrc;
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err = ip_mc_gsfget(sk, &gsf, p->gf_slist);
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err = ip_mc_gsfget(sk, &gsf, p->gf_slist_flex);
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if (err)
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return err;
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if (gsf.gf_numsrc < num)
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@ -1481,7 +1482,7 @@ static int ip_get_mcast_msfilter(struct sock *sk, void __user *optval,
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static int compat_ip_get_mcast_msfilter(struct sock *sk, void __user *optval,
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int __user *optlen, int len)
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{
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const int size0 = offsetof(struct compat_group_filter, gf_slist);
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const int size0 = offsetof(struct compat_group_filter, gf_slist_flex);
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struct compat_group_filter __user *p = optval;
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struct compat_group_filter gf32;
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struct group_filter gf;
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@ -1498,7 +1499,7 @@ static int compat_ip_get_mcast_msfilter(struct sock *sk, void __user *optval,
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num = gf.gf_numsrc = gf32.gf_numsrc;
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gf.gf_group = gf32.gf_group;
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err = ip_mc_gsfget(sk, &gf, p->gf_slist);
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err = ip_mc_gsfget(sk, &gf, p->gf_slist_flex);
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if (err)
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return err;
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if (gf.gf_numsrc < num)
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@ -225,7 +225,7 @@ static int ipv6_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
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if (GROUP_FILTER_SIZE(gsf->gf_numsrc) > optlen)
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goto out_free_gsf;
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ret = ip6_mc_msfilter(sk, gsf, gsf->gf_slist);
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ret = ip6_mc_msfilter(sk, gsf, gsf->gf_slist_flex);
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out_free_gsf:
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kfree(gsf);
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return ret;
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@ -234,7 +234,7 @@ out_free_gsf:
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static int compat_ipv6_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
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int optlen)
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{
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const int size0 = offsetof(struct compat_group_filter, gf_slist);
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const int size0 = offsetof(struct compat_group_filter, gf_slist_flex);
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struct compat_group_filter *gf32;
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void *p;
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int ret;
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@ -249,7 +249,7 @@ static int compat_ipv6_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
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if (!p)
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return -ENOMEM;
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gf32 = p + 4; /* we want ->gf_group and ->gf_slist aligned */
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gf32 = p + 4; /* we want ->gf_group and ->gf_slist_flex aligned */
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ret = -EFAULT;
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if (copy_from_sockptr(gf32, optval, optlen))
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goto out_free_p;
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@ -261,14 +261,14 @@ static int compat_ipv6_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
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goto out_free_p;
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ret = -EINVAL;
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if (offsetof(struct compat_group_filter, gf_slist[n]) > optlen)
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if (offsetof(struct compat_group_filter, gf_slist_flex[n]) > optlen)
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goto out_free_p;
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ret = ip6_mc_msfilter(sk, &(struct group_filter){
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.gf_interface = gf32->gf_interface,
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.gf_group = gf32->gf_group,
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.gf_fmode = gf32->gf_fmode,
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.gf_numsrc = gf32->gf_numsrc}, gf32->gf_slist);
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.gf_numsrc = gf32->gf_numsrc}, gf32->gf_slist_flex);
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out_free_p:
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kfree(p);
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@ -1048,7 +1048,7 @@ static int ipv6_getsockopt_sticky(struct sock *sk, struct ipv6_txoptions *opt,
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static int ipv6_get_msfilter(struct sock *sk, void __user *optval,
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int __user *optlen, int len)
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{
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const int size0 = offsetof(struct group_filter, gf_slist);
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const int size0 = offsetof(struct group_filter, gf_slist_flex);
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struct group_filter __user *p = optval;
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struct group_filter gsf;
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int num;
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@ -1062,7 +1062,7 @@ static int ipv6_get_msfilter(struct sock *sk, void __user *optval,
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return -EADDRNOTAVAIL;
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num = gsf.gf_numsrc;
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lock_sock(sk);
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err = ip6_mc_msfget(sk, &gsf, p->gf_slist);
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err = ip6_mc_msfget(sk, &gsf, p->gf_slist_flex);
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if (!err) {
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if (num > gsf.gf_numsrc)
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num = gsf.gf_numsrc;
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@ -1077,7 +1077,7 @@ static int ipv6_get_msfilter(struct sock *sk, void __user *optval,
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static int compat_ipv6_get_msfilter(struct sock *sk, void __user *optval,
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int __user *optlen)
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{
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const int size0 = offsetof(struct compat_group_filter, gf_slist);
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const int size0 = offsetof(struct compat_group_filter, gf_slist_flex);
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struct compat_group_filter __user *p = optval;
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struct compat_group_filter gf32;
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struct group_filter gf;
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@ -1100,7 +1100,7 @@ static int compat_ipv6_get_msfilter(struct sock *sk, void __user *optval,
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return -EADDRNOTAVAIL;
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lock_sock(sk);
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err = ip6_mc_msfget(sk, &gf, p->gf_slist);
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err = ip6_mc_msfget(sk, &gf, p->gf_slist_flex);
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release_sock(sk);
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if (err)
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return err;
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