4.17-stable review patch. If anyone has any objections, please let me know.
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From: Willem de Bruijn willemb@google.com
commit 4576cd469d980317c4edd9173f8b694aa71ea3a3 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/packet/af_packet.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
--- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -4258,6 +4258,8 @@ static int packet_set_ring(struct sock * }
if (req->tp_block_nr) { + unsigned int min_frame_size; + /* Sanity tests and some calculations */ err = -EBUSY; if (unlikely(rb->pg_vec)) @@ -4280,12 +4282,12 @@ static int packet_set_ring(struct sock * 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;