path: root/fs/splice.c
diff options
authorDarrick J. Wong <darrick.wong@oracle.com>2018-11-30 10:37:49 -0800
committerDarrick J. Wong <darrick.wong@oracle.com>2018-12-04 08:50:49 -0800
commit17614445576b6af24e9cf36607c6448164719c96 (patch)
treeb05471db334d90a6c2ba14693a6831d3544bce16 /fs/splice.c
parentvfs: allow some remap flags to be passed to vfs_clone_file_range (diff)
splice: don't read more than available pipe space
In commit 4721a601099, we tried to fix a problem wherein directio reads into a splice pipe will bounce EFAULT/EAGAIN all the way out to userspace by simulating a zero-byte short read. This happens because some directio read implementations (xfs) will call bio_iov_iter_get_pages to grab pipe buffer pages and issue asynchronous reads, but as soon as we run out of pipe buffers that _get_pages call returns EFAULT, which the splice code translates to EAGAIN and bounces out to userspace. In that commit, the iomap code catches the EFAULT and simulates a zero-byte read, but that causes assertion errors on regular splice reads because xfs doesn't allow short directio reads. The brokenness is compounded by splice_direct_to_actor immediately bailing on do_splice_to returning <= 0 without ever calling ->actor (which empties out the pipe), so if userspace calls back we'll EFAULT again on the full pipe, and nothing ever gets copied. Therefore, teach splice_direct_to_actor to clamp its requests to the amount of free space in the pipe and remove the simulated short read from the iomap directio code. Fixes: 4721a601099 ("iomap: dio data corruption and spurious errors when pipes fill") Reported-by: Murphy Zhou <jencce.kernel@gmail.com> Ranted-by: Amir Goldstein <amir73il@gmail.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Diffstat (limited to 'fs/splice.c')
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/splice.c b/fs/splice.c
index 3553f1956508..de2ede048473 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -945,11 +945,16 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
sd->flags &= ~SPLICE_F_NONBLOCK;
more = sd->flags & SPLICE_F_MORE;
+ WARN_ON_ONCE(pipe->nrbufs != 0);
while (len) {
size_t read_len;
loff_t pos = sd->pos, prev_pos = pos;
- ret = do_splice_to(in, &pos, pipe, len, flags);
+ /* Don't try to read more the pipe has space for. */
+ read_len = min_t(size_t, len,
+ (pipe->buffers - pipe->nrbufs) << PAGE_SHIFT);
+ ret = do_splice_to(in, &pos, pipe, read_len, flags);
if (unlikely(ret <= 0))
goto out_release;