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authorIlya Dryomov <idryomov@gmail.com>2018-11-08 15:55:37 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-11-27 16:10:51 +0100
commit3c7f1671af5f1bef6fac4e9ad7416e7a5a4ed295 (patch)
tree20bb0336e3a0d1b9975e9eaf5185778925cff84e
parent540f89376ba2949f53ed6f057fea321be848cd43 (diff)
libceph: fall back to sendmsg for slab pages
commit 7e241f647dc7087a0401418a187f3f5b527cc690 upstream. skb_can_coalesce() allows coalescing neighboring slab objects into a single frag: return page == skb_frag_page(frag) && off == frag->page_offset + skb_frag_size(frag); ceph_tcp_sendpage() can be handed slab pages. One example of this is XFS: it passes down sector sized slab objects for its metadata I/O. If the kernel client is co-located on the OSD node, the skb may go through loopback and pop on the receive side with the exact same set of frags. When tcp_recvmsg() attempts to copy out such a frag, hardened usercopy complains because the size exceeds the object's allocated size: usercopy: kernel memory exposure attempt detected from ffff9ba917f20a00 (kmalloc-512) (1024 bytes) Although skb_can_coalesce() could be taught to return false if the resulting frag would cross a slab object boundary, we already have a fallback for non-refcounted pages. Utilize it for slab pages too. Cc: stable@vger.kernel.org # 4.8+ Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--net/ceph/messenger.c12
1 files changed, 9 insertions, 3 deletions
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 5c4e85296cf6..5281da82371a 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -594,9 +594,15 @@ static int ceph_tcp_sendpage(struct socket *sock, struct page *page,
struct bio_vec bvec;
int ret;
- /* sendpage cannot properly handle pages with page_count == 0,
- * we need to fallback to sendmsg if that's the case */
- if (page_count(page) >= 1)
+ /*
+ * sendpage cannot properly handle pages with page_count == 0,
+ * we need to fall back to sendmsg if that's the case.
+ *
+ * Same goes for slab pages: skb_can_coalesce() allows
+ * coalescing neighboring slab objects into a single frag which
+ * triggers one of hardened usercopy checks.
+ */
+ if (page_count(page) >= 1 && !PageSlab(page))
return __ceph_tcp_sendpage(sock, page, offset, size, more);
bvec.bv_page = page;