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    Subject[PATCH 3.18 43/56] fuse: Dont access pipe->buffers without pipe_lock()
    Date
    3.18-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Andrey Ryabinin <aryabinin@virtuozzo.com>

    commit a2477b0e67c52f4364a47c3ad70902bc2a61bd4c upstream.

    fuse_dev_splice_write() reads pipe->buffers to determine the size of
    'bufs' array before taking the pipe_lock(). This is not safe as
    another thread might change the 'pipe->buffers' between the allocation
    and taking the pipe_lock(). So we end up with too small 'bufs' array.

    Move the bufs allocations inside pipe_lock()/pipe_unlock() to fix this.

    Fixes: dd3bb14f44a6 ("fuse: support splice() writing to fuse device")
    Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
    Cc: <stable@vger.kernel.org> # v2.6.35
    Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/fuse/dev.c | 7 +++++--
    1 file changed, 5 insertions(+), 2 deletions(-)

    --- a/fs/fuse/dev.c
    +++ b/fs/fuse/dev.c
    @@ -1913,11 +1913,14 @@ static ssize_t fuse_dev_splice_write(str
    if (!fc)
    return -EPERM;

    + pipe_lock(pipe);
    +
    bufs = kmalloc(pipe->buffers * sizeof(struct pipe_buffer), GFP_KERNEL);
    - if (!bufs)
    + if (!bufs) {
    + pipe_unlock(pipe);
    return -ENOMEM;
    + }

    - pipe_lock(pipe);
    nbuf = 0;
    rem = 0;
    for (idx = 0; idx < pipe->nrbufs && rem < len; idx++)

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