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net/ipv4/ipv6: Replace one-element arraya with flexible-array members

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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 2021-08-04 15:45:36 -05:00 committed by David S. Miller
parent d15040a338
commit db243b7964
4 changed files with 55 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
include/net/compat.h
View File

@ -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 */

21
include/uapi/linux/in.h
View File

@ -222,11 +222,22 @@ struct group_source_req {
};
struct group_filter {
__u32 gf_interface; /* interface index */
struct __kernel_sockaddr_storage gf_group; /* multicast address */
__u32 gf_fmode; /* filter mode */
__u32 gf_numsrc; /* number of sources */
struct __kernel_sockaddr_storage gf_slist[1]; /* interface index */
union {
struct {
__u32 gf_interface_aux; /* interface index */
struct __kernel_sockaddr_storage gf_group_aux; /* multicast address */
__u32 gf_fmode_aux; /* filter mode */
__u32 gf_numsrc_aux; /* number of sources */
struct __kernel_sockaddr_storage gf_slist[1]; /* interface index */
};
struct {
__u32 gf_interface; /* interface index */
struct __kernel_sockaddr_storage gf_group; /* multicast address */
__u32 gf_fmode; /* filter mode */
__u32 gf_numsrc; /* number of sources */
struct __kernel_sockaddr_storage gf_slist_flex[]; /* interface index */
};
};
};
#define GROUP_FILTER_SIZE(numsrc) \

19
net/ipv4/ip_sockglue.c
View File

@ -790,7 +790,8 @@ static int ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval, int optlen)
goto out_free_gsf;
err = set_mcast_msfilter(sk, gsf->gf_interface, gsf->gf_numsrc,
gsf->gf_fmode, &gsf->gf_group, gsf->gf_slist);
gsf->gf_fmode, &gsf->gf_group,
gsf->gf_slist_flex);
out_free_gsf:
kfree(gsf);
return err;
@ -799,7 +800,7 @@ out_free_gsf:
static int compat_ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
int optlen)
{
const int size0 = offsetof(struct compat_group_filter, gf_slist);
const int size0 = offsetof(struct compat_group_filter, gf_slist_flex);
struct compat_group_filter *gf32;
unsigned int n;
void *p;
@ -813,7 +814,7 @@ static int compat_ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
p = kmalloc(optlen + 4, GFP_KERNEL);
if (!p)
return -ENOMEM;
gf32 = p + 4; /* we want ->gf_group and ->gf_slist aligned */
gf32 = p + 4; /* we want ->gf_group and ->gf_slist_flex aligned */
err = -EFAULT;
if (copy_from_sockptr(gf32, optval, optlen))
@ -826,7 +827,7 @@ static int compat_ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
goto out_free_gsf;
err = -EINVAL;
if (offsetof(struct compat_group_filter, gf_slist[n]) > optlen)
if (offsetof(struct compat_group_filter, gf_slist_flex[n]) > optlen)
goto out_free_gsf;
/* numsrc >= (4G-140)/128 overflow in 32 bits */
@ -834,7 +835,7 @@ static int compat_ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
if (n > sock_net(sk)->ipv4.sysctl_igmp_max_msf)
goto out_free_gsf;
err = set_mcast_msfilter(sk, gf32->gf_interface, n, gf32->gf_fmode,
&gf32->gf_group, gf32->gf_slist);
&gf32->gf_group, gf32->gf_slist_flex);
out_free_gsf:
kfree(p);
return err;
@ -1455,7 +1456,7 @@ static bool getsockopt_needs_rtnl(int optname)
static int ip_get_mcast_msfilter(struct sock *sk, void __user *optval,
int __user *optlen, int len)
{
const int size0 = offsetof(struct group_filter, gf_slist);
const int size0 = offsetof(struct group_filter, gf_slist_flex);
struct group_filter __user *p = optval;
struct group_filter gsf;
int num;
@ -1467,7 +1468,7 @@ static int ip_get_mcast_msfilter(struct sock *sk, void __user *optval,
return -EFAULT;
num = gsf.gf_numsrc;
err = ip_mc_gsfget(sk, &gsf, p->gf_slist);
err = ip_mc_gsfget(sk, &gsf, p->gf_slist_flex);
if (err)
return err;
if (gsf.gf_numsrc < num)
@ -1481,7 +1482,7 @@ static int ip_get_mcast_msfilter(struct sock *sk, void __user *optval,
static int compat_ip_get_mcast_msfilter(struct sock *sk, void __user *optval,
int __user *optlen, int len)
{
const int size0 = offsetof(struct compat_group_filter, gf_slist);
const int size0 = offsetof(struct compat_group_filter, gf_slist_flex);
struct compat_group_filter __user *p = optval;
struct compat_group_filter gf32;
struct group_filter gf;
@ -1498,7 +1499,7 @@ static int compat_ip_get_mcast_msfilter(struct sock *sk, void __user *optval,
num = gf.gf_numsrc = gf32.gf_numsrc;
gf.gf_group = gf32.gf_group;
err = ip_mc_gsfget(sk, &gf, p->gf_slist);
err = ip_mc_gsfget(sk, &gf, p->gf_slist_flex);
if (err)
return err;
if (gf.gf_numsrc < num)

18
net/ipv6/ipv6_sockglue.c
View File

@ -225,7 +225,7 @@ static int ipv6_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
if (GROUP_FILTER_SIZE(gsf->gf_numsrc) > optlen)
goto out_free_gsf;
ret = ip6_mc_msfilter(sk, gsf, gsf->gf_slist);
ret = ip6_mc_msfilter(sk, gsf, gsf->gf_slist_flex);
out_free_gsf:
kfree(gsf);
return ret;
@ -234,7 +234,7 @@ out_free_gsf:
static int compat_ipv6_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
int optlen)
{
const int size0 = offsetof(struct compat_group_filter, gf_slist);
const int size0 = offsetof(struct compat_group_filter, gf_slist_flex);
struct compat_group_filter *gf32;
void *p;
int ret;
@ -249,7 +249,7 @@ static int compat_ipv6_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
if (!p)
return -ENOMEM;
gf32 = p + 4; /* we want ->gf_group and ->gf_slist aligned */
gf32 = p + 4; /* we want ->gf_group and ->gf_slist_flex aligned */
ret = -EFAULT;
if (copy_from_sockptr(gf32, optval, optlen))
goto out_free_p;
@ -261,14 +261,14 @@ static int compat_ipv6_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
goto out_free_p;
ret = -EINVAL;
if (offsetof(struct compat_group_filter, gf_slist[n]) > optlen)
if (offsetof(struct compat_group_filter, gf_slist_flex[n]) > optlen)
goto out_free_p;
ret = ip6_mc_msfilter(sk, &(struct group_filter){
.gf_interface = gf32->gf_interface,
.gf_group = gf32->gf_group,
.gf_fmode = gf32->gf_fmode,
.gf_numsrc = gf32->gf_numsrc}, gf32->gf_slist);
.gf_numsrc = gf32->gf_numsrc}, gf32->gf_slist_flex);
out_free_p:
kfree(p);
@ -1048,7 +1048,7 @@ static int ipv6_getsockopt_sticky(struct sock *sk, struct ipv6_txoptions *opt,
static int ipv6_get_msfilter(struct sock *sk, void __user *optval,
int __user *optlen, int len)
{
const int size0 = offsetof(struct group_filter, gf_slist);
const int size0 = offsetof(struct group_filter, gf_slist_flex);
struct group_filter __user *p = optval;
struct group_filter gsf;
int num;
@ -1062,7 +1062,7 @@ static int ipv6_get_msfilter(struct sock *sk, void __user *optval,
return -EADDRNOTAVAIL;
num = gsf.gf_numsrc;
lock_sock(sk);
err = ip6_mc_msfget(sk, &gsf, p->gf_slist);
err = ip6_mc_msfget(sk, &gsf, p->gf_slist_flex);
if (!err) {
if (num > gsf.gf_numsrc)
num = gsf.gf_numsrc;
@ -1077,7 +1077,7 @@ static int ipv6_get_msfilter(struct sock *sk, void __user *optval,
static int compat_ipv6_get_msfilter(struct sock *sk, void __user *optval,
int __user *optlen)
{
const int size0 = offsetof(struct compat_group_filter, gf_slist);
const int size0 = offsetof(struct compat_group_filter, gf_slist_flex);
struct compat_group_filter __user *p = optval;
struct compat_group_filter gf32;
struct group_filter gf;
@ -1100,7 +1100,7 @@ static int compat_ipv6_get_msfilter(struct sock *sk, void __user *optval,
return -EADDRNOTAVAIL;
lock_sock(sk);
err = ip6_mc_msfget(sk, &gf, p->gf_slist);
err = ip6_mc_msfget(sk, &gf, p->gf_slist_flex);
release_sock(sk);
if (err)
return err;