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Subject: [PATCH 0/2] pipe: Fixes [ver #2]
From:   David Howells <dhowells@redhat.com>
To:     torvalds@linux-foundation.org, ebiggers@kernel.org
Cc:     dhowells@redhat.com, viro@zeniv.linux.org.uk,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Thu, 05 Dec 2019 22:30:22 +0000
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Hi Linus, Eric,

Here are a couple of patches to fix bugs syzbot found in the pipe changes:

 (1) An assertion check will sometimes trip when polling a pipe because the
     ring size and indices used are approximate and may be being changed
     simultaneously.

     An equivalent approximate calculation was done previously, but without
     the assertion check, so I've just dropped the check.  To make it
     accurate, the pipe mutex would need to be taken or the spin lock could
     be used - but usage of the spinlock would need to be rolled out into
     splice, iov_iter and other places for that.

 (2) The index mask and the max_usage values cannot be cached across
     pipe_wait() as F_SETPIPE_SZ could have been called during the wait.
     This can cause pipe_write() to break.

David
---
David Howells (2):
      pipe: Remove assertion from pipe_poll()
      pipe: Fix missing mask update after pipe_wait()


 fs/pipe.c |   21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)