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authorJeff Layton <jlayton@redhat.com>2014-02-14 12:20:35 (GMT)
committerJiri Slaby <jslaby@suse.cz>2014-03-05 16:13:41 (GMT)
commit90d369693d48ec7ffa4ca039e6fd14e861486251 (patch)
tree5ea3253e491387aa3a9f7b0aefbbc1d4f2470c1c /Documentation/filesystems/caching
parent92ffeda00eeff3b33f9a41011d9ac5779d2eb131 (diff)
downloadlinux-fsl-qoriq-90d369693d48ec7ffa4ca039e6fd14e861486251.tar.xz
cifs: ensure that uncached writes handle unmapped areas correctly
commit 5d81de8e8667da7135d3a32a964087c0faf5483f upstream. It's possible for userland to pass down an iovec via writev() that has a bogus user pointer in it. If that happens and we're doing an uncached write, then we can end up getting less bytes than we expect from the call to iov_iter_copy_from_user. This is CVE-2014-0069 cifs_iovec_write isn't set up to handle that situation however. It'll blindly keep chugging through the page array and not filling those pages with anything useful. Worse yet, we'll later end up with a negative number in wdata->tailsz, which will confuse the sending routines and cause an oops at the very least. Fix this by having the copy phase of cifs_iovec_write stop copying data in this situation and send the last write as a short one. At the same time, we want to avoid sending a zero-length write to the server, so break out of the loop and set rc to -EFAULT if that happens. This also allows us to handle the case where no address in the iovec is valid. [Note: Marking this for stable on v3.4+ kernels, but kernels as old as v2.6.38 may have a similar problem and may need similar fix] Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru> Reported-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Steve French <smfrench@gmail.com> Signed-off-by: Jiri Slaby <jslaby@suse.cz>
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