[PATCH] Fix 32bit sendmsg() flaw
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>
diff --git a/net/compat.c b/net/compat.c
index d99ab96..e593dac 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -135,13 +135,14 @@
* 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 @@
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 @@
* 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 @@
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)