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SubjectRe: [PATCH v2 1/3] fs/fuse, splice_write: Don't access pipe->buffers without pipe_lock()
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On 7/17/18 6:00 PM, Andrey Ryabinin wrote:
> 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>

BTW, why don't we need to do the same in fuse_dev_splice_read()?

Thanks,
Vlastimil

> ---
> fs/fuse/dev.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index c6b88fa85e2e..702592cce546 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -1944,12 +1944,15 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
> if (!fud)
> return -EPERM;
>
> + pipe_lock(pipe);
> +
> bufs = kmalloc_array(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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