From: Pavel Begunkov asml.silence@gmail.com

[ Upstream commit 0f1d344feb534555a0dcd0beafb7211a37c5355e ]

iter_file_splice_write() may spawn bvec segments with zero-length. In preparation for prohibiting them, filter out by hand at splice level.

Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: Pavel Begunkov asml.silence@gmail.com Reviewed-by: Ming Lei ming.lei@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Thadeu Lima de Souza Cascardo cascardo@igalia.com --- fs/splice.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/splice.c b/fs/splice.c index 866d5c2367b2..474fb8b5562a 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -662,12 +662,14 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,

/* build the vector */ left = sd.total_len; - for (n = 0; !pipe_empty(head, tail) && left && n < nbufs; tail++, n++) { + for (n = 0; !pipe_empty(head, tail) && left && n < nbufs; tail++) { struct pipe_buffer *buf = &pipe->bufs[tail & mask]; size_t this_len = buf->len;

- if (this_len > left) - this_len = left; + /* zero-length bvecs are not supported, skip them */ + if (!this_len) + continue; + this_len = min(this_len, left);

ret = pipe_buf_confirm(pipe, buf); if (unlikely(ret)) { @@ -680,6 +682,7 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out, array[n].bv_len = this_len; array[n].bv_offset = buf->offset; left -= this_len; + n++; }

iov_iter_bvec(&from, WRITE, array, n, sd.total_len - left);