diff options
authorWillem de Bruijn <willemb@google.com>2018-08-06 10:38:34 -0400
committerDavid S. Miller <davem@davemloft.net>2018-08-06 13:48:33 -0700
commit4576cd469d980317c4edd9173f8b694aa71ea3a3 (patch)
parent82a40777de12728dedf4075453b694f0d1baee80 (diff)
packet: refine ring v3 block size test to hold one frame
TPACKET_V3 stores variable length frames in fixed length blocks. Blocks must be able to store a block header, optional private space and at least one minimum sized frame. Frames, even for a zero snaplen packet, store metadata headers and optional reserved space. In the block size bounds check, ensure that the frame of the chosen configuration fits. This includes sockaddr_ll and optional tp_reserve. Syzbot was able to construct a ring with insuffient room for the sockaddr_ll in the header of a zero-length frame, triggering an out-of-bounds write in dev_parse_header. Convert the comparison to less than, as zero is a valid snap len. This matches the test for minimum tp_frame_size immediately below. Fixes: f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation.") Fixes: eb73190f4fbe ("net/packet: refine check for priv area size") Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Willem de Bruijn <willemb@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
1 files changed, 6 insertions, 4 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 9b27d0cd766d..e6445d8f3f57 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -4226,6 +4226,8 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
if (req->tp_block_nr) {
+ unsigned int min_frame_size;
/* Sanity tests and some calculations */
err = -EBUSY;
if (unlikely(rb->pg_vec))
@@ -4248,12 +4250,12 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
goto out;
if (unlikely(!PAGE_ALIGNED(req->tp_block_size)))
goto out;
+ min_frame_size = po->tp_hdrlen + po->tp_reserve;
if (po->tp_version >= TPACKET_V3 &&
- req->tp_block_size <=
- BLK_PLUS_PRIV((u64)req_u->req3.tp_sizeof_priv) + sizeof(struct tpacket3_hdr))
+ req->tp_block_size <
+ BLK_PLUS_PRIV((u64)req_u->req3.tp_sizeof_priv) + min_frame_size)
goto out;
- if (unlikely(req->tp_frame_size < po->tp_hdrlen +
- po->tp_reserve))
+ if (unlikely(req->tp_frame_size < min_frame_size))
goto out;
if (unlikely(req->tp_frame_size & (TPACKET_ALIGNMENT - 1)))
goto out;