sendfile(): check f_op.splice_write() rather than f_op.sendpage()

sendfile(2) was reworked with the splice infrastructure, but it still
checks f_op.sendpage() instead of f_op.splice_write() wrongly.  Although
if f_op.sendpage() exists, f_op.splice_write() always exists at the same
time currently, the assumption will be broken in future silently.  This
patch also brings a side effect: sendfile(2) can work with any output
file.  Some security checks related to f_op are added too.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 0 insertions, 2 deletions

diff --git a/fs/read_write.c b/fs/read_write.c
index 3ac28987f22a..b7f4a1f94d48 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -826,8 +826,6 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
         if (!(out_file->f_mode & FMODE_WRITE))
                 goto fput_out;
         retval = -EINVAL;
-        if (!out_file->f_op || !out_file->f_op->sendpage)
-                goto fput_out;
         in_inode = in_file->f_path.dentry->d_inode;
         out_inode = out_file->f_path.dentry->d_inode;
         retval = rw_verify_area(WRITE, out_file, &out_file->f_pos, count);