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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)
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parent82a40777de12728dedf4075453b694f0d1baee80 (diff)
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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>
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