From: Darrick J. Wong darrick.wong@oracle.com
commit 3253d9d093376d62b4a56e609f15d2ec5085ac73 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/splice.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
--- a/fs/splice.c +++ b/fs/splice.c @@ -949,12 +949,13 @@ ssize_t splice_direct_to_actor(struct fi 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; @@ -1175,8 +1176,15 @@ static long do_splice(struct file *in, l
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);