From 3253d9d093376d62b4a56e609f15d2ec5085ac73 Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Tue, 15 Oct 2019 08:44:32 -0700 Subject: [PATCH] splice: only read in as much information as there is pipe buffer space MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Andreas Grünbacher Signed-off-by: Darrick J. Wong --- fs/splice.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/fs/splice.c b/fs/splice.c index 98412721f056..e509239d7e06 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -945,12 +945,13 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd, 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 @@ static long do_splice(struct file *in, loff_t __user *off_in, 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);