diff options
| author | Willem de Bruijn <willemb@google.com> | 2018-08-06 10:38:34 -0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-08-06 13:48:33 -0700 |
| commit | 4576cd469d980317c4edd9173f8b694aa71ea3a3 (patch) | |
| tree | a5d25cfbaa8b5ca12b8a1c3c6094326c220a786a /net | |
| parent | 82a40777de12728dedf4075453b694f0d1baee80 (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>
Diffstat (limited to 'net')
| -rw-r--r-- | net/packet/af_packet.c | 10 |
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; |