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splice: don't generate zero-len segement bvecs

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commit 0f1d344feb534555a0dcd0beafb7211a37c5355e upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Pavel Begunkov 2021-01-09 16:02:57 +00:00 committed by Greg Kroah-Hartman
parent bf0b0c6d15
commit 982a2757e7
1 changed files with 6 additions and 3 deletions
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9
fs/splice.c
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@ -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);