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[PATCH] Fix 32bit sendmsg() flaw

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When we copy 32bit ->msg_control contents to kernel, we walk the same
userland data twice without sanity checks on the second pass.

Second version of this patch: the original broke with 64-bit arches
running 32-bit-compat-mode executables doing sendmsg() syscalls with
unaligned CMSG data areas

Another thing is that we use kmalloc() to allocate and sock_kfree_s()
to free afterwards; less serious, but also needs fixing.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Chris Wright <chrisw@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Al Viro 2005-09-07 18:28:51 -07:00 committed by Linus Torvalds
parent 5aa3b610a7
commit 8920e8f94c
3 changed files with 29 additions and 20 deletions
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2
include/net/compat.h
View file

@ -33,7 +33,7 @@ extern asmlinkage long compat_sys_sendmsg(int,struct compat_msghdr __user *,unsi
extern asmlinkage long compat_sys_recvmsg(int,struct compat_msghdr __user *,unsigned);
extern asmlinkage long compat_sys_getsockopt(int, int, int, char __user *, int __user *);
extern int put_cmsg_compat(struct msghdr*, int, int, int, void *);
extern int cmsghdr_from_user_compat_to_kern(struct msghdr *, unsigned char *,
extern int cmsghdr_from_user_compat_to_kern(struct msghdr *, struct sock *, unsigned char *,
int);
#endif /* NET_COMPAT_H */

44
net/compat.c
View file

@ -135,13 +135,14 @@ static inline struct compat_cmsghdr __user *cmsg_compat_nxthdr(struct msghdr *ms
* thus placement) of cmsg headers and length are different for
* 32-bit apps. -DaveM
*/
int cmsghdr_from_user_compat_to_kern(struct msghdr *kmsg,
int cmsghdr_from_user_compat_to_kern(struct msghdr *kmsg, struct sock *sk,
unsigned char *stackbuf, int stackbuf_size)
{
struct compat_cmsghdr __user *ucmsg;
struct cmsghdr *kcmsg, *kcmsg_base;
compat_size_t ucmlen;
__kernel_size_t kcmlen, tmp;
int err = -EFAULT;
kcmlen = 0;
kcmsg_base = kcmsg = (struct cmsghdr *)stackbuf;
@ -156,6 +157,7 @@ int cmsghdr_from_user_compat_to_kern(struct msghdr *kmsg,
tmp = ((ucmlen - CMSG_COMPAT_ALIGN(sizeof(*ucmsg))) +
CMSG_ALIGN(sizeof(struct cmsghdr)));
tmp = CMSG_ALIGN(tmp);
kcmlen += tmp;
ucmsg = cmsg_compat_nxthdr(kmsg, ucmsg, ucmlen);
}
@ -167,30 +169,34 @@ int cmsghdr_from_user_compat_to_kern(struct msghdr *kmsg,
* until we have successfully copied over all of the data
* from the user.
*/
if(kcmlen > stackbuf_size)
kcmsg_base = kcmsg = kmalloc(kcmlen, GFP_KERNEL);
if(kcmsg == NULL)
if (kcmlen > stackbuf_size)
kcmsg_base = kcmsg = sock_kmalloc(sk, kcmlen, GFP_KERNEL);
if (kcmsg == NULL)
return -ENOBUFS;
/* Now copy them over neatly. */
memset(kcmsg, 0, kcmlen);
ucmsg = CMSG_COMPAT_FIRSTHDR(kmsg);
while(ucmsg != NULL) {
__get_user(ucmlen, &ucmsg->cmsg_len);
if (__get_user(ucmlen, &ucmsg->cmsg_len))
goto Efault;
if (!CMSG_COMPAT_OK(ucmlen, ucmsg, kmsg))
goto Einval;
tmp = ((ucmlen - CMSG_COMPAT_ALIGN(sizeof(*ucmsg))) +
CMSG_ALIGN(sizeof(struct cmsghdr)));
if ((char *)kcmsg_base + kcmlen - (char *)kcmsg < CMSG_ALIGN(tmp))
goto Einval;
kcmsg->cmsg_len = tmp;
__get_user(kcmsg->cmsg_level, &ucmsg->cmsg_level);
__get_user(kcmsg->cmsg_type, &ucmsg->cmsg_type);
/* Copy over the data. */
if(copy_from_user(CMSG_DATA(kcmsg),
CMSG_COMPAT_DATA(ucmsg),
(ucmlen - CMSG_COMPAT_ALIGN(sizeof(*ucmsg)))))
goto out_free_efault;
tmp = CMSG_ALIGN(tmp);
if (__get_user(kcmsg->cmsg_level, &ucmsg->cmsg_level) ||
__get_user(kcmsg->cmsg_type, &ucmsg->cmsg_type) ||
copy_from_user(CMSG_DATA(kcmsg),
CMSG_COMPAT_DATA(ucmsg),
(ucmlen - CMSG_COMPAT_ALIGN(sizeof(*ucmsg)))))
goto Efault;
/* Advance. */
kcmsg = (struct cmsghdr *)((char *)kcmsg + CMSG_ALIGN(tmp));
kcmsg = (struct cmsghdr *)((char *)kcmsg + tmp);
ucmsg = cmsg_compat_nxthdr(kmsg, ucmsg, ucmlen);
}
@ -199,10 +205,12 @@ int cmsghdr_from_user_compat_to_kern(struct msghdr *kmsg,
kmsg->msg_controllen = kcmlen;
return 0;
out_free_efault:
if(kcmsg_base != (struct cmsghdr *)stackbuf)
kfree(kcmsg_base);
return -EFAULT;
Einval:
err = -EINVAL;
Efault:
if (kcmsg_base != (struct cmsghdr *)stackbuf)
sock_kfree_s(sk, kcmsg_base, kcmlen);
return err;
}
int put_cmsg_compat(struct msghdr *kmsg, int level, int type, int len, void *data)

3
net/socket.c
View file

@ -1745,10 +1745,11 @@ asmlinkage long sys_sendmsg(int fd, struct msghdr __user *msg, unsigned flags)
goto out_freeiov;
ctl_len = msg_sys.msg_controllen;
if ((MSG_CMSG_COMPAT & flags) && ctl_len) {
err = cmsghdr_from_user_compat_to_kern(&msg_sys, ctl, sizeof(ctl));
err = cmsghdr_from_user_compat_to_kern(&msg_sys, sock->sk, ctl, sizeof(ctl));
if (err)
goto out_freeiov;
ctl_buf = msg_sys.msg_control;
ctl_len = msg_sys.msg_controllen;
} else if (ctl_len) {
if (ctl_len > sizeof(ctl))
{