From: Darrick J. Wong Date: Tue, 15 Oct 2019 15:44:32 +0000 (-0700) Subject: splice: only read in as much information as there is pipe buffer space X-Git-Tag: v5.3.17~11 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=acdd98046288d9113aad152dc8d1341dd602afc7;p=thirdparty%2Fkernel%2Fstable.git splice: only read in as much information as there is pipe buffer space 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 Reviewed-by: Andreas Grünbacher Signed-off-by: Darrick J. Wong Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/splice.c b/fs/splice.c index 98412721f0562..e509239d7e06a 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);