[PATCH 02/15] splice: remove permission hook from do_splice_direct()

Amir Goldstein
2023-11-14T15:33:07Z

All callers of do_splice_direct() have a call to rw_verify_area() for
the entire range that is being copied, e.g. by vfs_copy_file_range() or
do_sendfile() before calling do_splice_direct().

The rw_verify_area() check inside do_splice_direct() is redundant and
is called after sb_start_write(), so it is not "start-write-safe".
Remove this redundant check.

This is needed for fanotify "pre content" events.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
fs/splice.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/fs/splice.c b/fs/splice.c
index d983d375ff11..6e917db6f49a 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1166,6 +1166,7 @@ static void direct_file_splice_eof(struct splice_desc *sd)
* (splice in + splice out, as compared to just sendfile()). So this helper
* can splice directly through a process-private pipe.
*
+ * Callers already called rw_verify_area() on the entire range.
*/
long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
loff_t *opos, size_t len, unsigned int flags)
@@ -1187,10 +1188,6 @@ long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
if (unlikely(out->f_flags & O_APPEND))
return -EINVAL;

- ret = rw_verify_area(WRITE, out, opos, len);
- if (unlikely(ret < 0))
- return ret;
-
ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
if (ret > 0)
*ppos = sd.pos;
--
2.34.1