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    SubjectRe: [PATCH 4.19 06/48] ALSA: seq: oss: Serialize ioctls
    Hi!

    > commit 80982c7e834e5d4e325b6ce33757012ecafdf0bb upstream.
    >
    > Some ioctls via OSS sequencer API may race and lead to UAF when the
    > port create and delete are performed concurrently, as spotted by a
    > couple of syzkaller cases. This patch is an attempt to address it by
    > serializing the ioctls with the existing register_mutex.
    >
    > Basically OSS sequencer API is an obsoleted interface and was designed
    > without much consideration of the concurrency. There are very few
    > applications with it, and the concurrent performance isn't asked,
    > hence this "big hammer" approach should be good enough.

    That really is a "big hammer". And I believe it is too big.

    In particular, do we need to drop the lock while sleeping in
    SNDCTL_SEQ_SYNC: => snd_seq_oss_writeq_sync ?

    Best regards,
    Pavel
    --
    DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
    HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
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