splice: only read in as much information as there is pipe buffer space
Andreas Grünbacher reports that on the two filesystems that support
iomap directio, it's possible for splice() to return -EAGAIN (instead of
a short splice) if the pipe being written to has less space available in
its pipe buffers than the length supplied by the calling process.
Months ago we fixed splice_direct_to_actor to clamp the length of the
read request to the size of the splice pipe. Do the same to do_splice.
Fixes: 17614445576b6 ("splice: don't read more than available pipe space")
Reported-by: syzbot+3c01db6025f26530cf8d@syzkaller.appspotmail.com
Reported-by: Andreas Grünbacher <andreas.gruenbacher@gmail.com>
Reviewed-by: Andreas Grünbacher <andreas.gruenbacher@gmail.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff --git a/fs/splice.c b/fs/splice.c
index 9841272..e509239 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -945,12 +945,13 @@
WARN_ON_ONCE(pipe->nrbufs != 0);
while (len) {
+ unsigned int pipe_pages;
size_t read_len;
loff_t pos = sd->pos, prev_pos = pos;
/* Don't try to read more the pipe has space for. */
- read_len = min_t(size_t, len,
- (pipe->buffers - pipe->nrbufs) << PAGE_SHIFT);
+ pipe_pages = pipe->buffers - pipe->nrbufs;
+ read_len = min(len, (size_t)pipe_pages << PAGE_SHIFT);
ret = do_splice_to(in, &pos, pipe, read_len, flags);
if (unlikely(ret <= 0))
goto out_release;
@@ -1180,8 +1181,15 @@
pipe_lock(opipe);
ret = wait_for_space(opipe, flags);
- if (!ret)
+ if (!ret) {
+ unsigned int pipe_pages;
+
+ /* Don't try to read more the pipe has space for. */
+ pipe_pages = opipe->buffers - opipe->nrbufs;
+ len = min(len, (size_t)pipe_pages << PAGE_SHIFT);
+
ret = do_splice_to(in, &offset, opipe, len, flags);
+ }
pipe_unlock(opipe);
if (ret > 0)
wakeup_pipe_readers(opipe);
