tree 33dbcccb975a1943c7f015e54f0ce148f2bbc3d5
parent 8f7e885a4cc167f8b1931800fa1319772ae4b11d
author Al Viro <viro@zeniv.linux.org.uk> 1426982898 -0400
committer Al Viro <viro@zeniv.linux.org.uk> 1428805633 -0400

sg_start_req(): make sure that there's not too many elements in iovec

unfortunately, allowing an arbitrary 16bit value means a possibility of
overflow in the calculation of total number of pages in bio_map_user_iov() -
we rely on there being no more than PAGE_SIZE members of sum in the
first loop there.  If that sum wraps around, we end up allocating
too small array of pointers to pages and it's easy to overflow it in
the second loop.

X-Coverup: TINC (and there's no lumber cartel either)
Cc: stable@vger.kernel.org # way, way back
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>