[PATCH 04/15] splice: move permission hook out of splice_file_to_pipe()

Amir Goldstein
2023-11-14T15:33:09Z

vfs_splice_read() has a permission hook inside rw_verify_area() and
it is called from splice_file_to_pipe(), which is called from
do_splice() and do_sendfile().

do_sendfile() already has a rw_verify_area() check for the entire range.
do_splice() has a rw_verify_check() for the splice to file case, not for
the splice from file case.

Add the rw_verify_area() check for splice from file case in do_splice()
and use a variant of vfs_splice_read() without rw_verify_area() check
in splice_file_to_pipe() to avoid the redundant rw_verify_area() checks.

This is needed for fanotify "pre content" events.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
fs/splice.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/splice.c b/fs/splice.c
index 6fc2c27e9520..d4fdd44c0b32 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1239,7 +1239,7 @@ long splice_file_to_pipe(struct file *in,
pipe_lock(opipe);
ret = wait_for_space(opipe, flags);
if (!ret)
- ret = vfs_splice_read(in, offset, opipe, len, flags);
+ ret = do_splice_read(in, offset, opipe, len, flags);
pipe_unlock(opipe);
if (ret > 0)
wakeup_pipe_readers(opipe);
@@ -1316,6 +1316,10 @@ long do_splice(struct file *in, loff_t *off_in, struct file *out,
offset = in->f_pos;
}

+ ret = rw_verify_area(READ, in, &offset, len);
+ if (unlikely(ret < 0))
+ return ret;
+
if (out->f_flags & O_NONBLOCK)
flags |= SPLICE_F_NONBLOCK;

--
2.34.1