[PATCH] fix: general protection fault in iter_file_splice_write

[Daniel Yang <danielyangkang@gmail.com>]

The function iter_file_splice_write() calls pipe_buf_release() which has
a nullptr dereference in ops->release. Add check for buf->ops not null
before calling pipe_buf_release().

Signed-off-by: Daniel Yang <danielyangkang@gmail.com>
Reported-by: syzbot+d2125fcb6aa8c4276fd2@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d2125fcb6aa8c4276fd2
Fixes: 2df86547b23d ("netfs: Cut over to using new writeback code")
---
 fs/splice.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/splice.c b/fs/splice.c
index 06232d7e5..b8c503e47 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -756,7 +756,8 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 			if (ret >= buf->len) {
 				ret -= buf->len;
 				buf->len = 0;
-				pipe_buf_release(pipe, buf);
+				if (buf->ops)
+					pipe_buf_release(pipe, buf);
 				tail++;
 				pipe->tail = tail;
 				if (pipe->files)
-- 
2.39.2