[PATCH 1/2] seccomp: allow addfd to transfer O_PATH descriptors

[Cong Wang <xiyou.wangcong@gmail.com>]

From: Cong Wang <cwang@multikernel.io>

SECCOMP_IOCTL_NOTIF_ADDFD uses fget() to acquire the supervisor's
source descriptor. fget() rejects FMODE_PATH files, so injecting an
O_PATH descriptor fails with EBADF before the receiving task can
install it.

Use fget_raw() to acquire the source file. This takes the same
reference while allowing FMODE_PATH. The existing receive_fd() and
receive_fd_replace() paths retain their security_file_receive()
checks and preserve the file's O_PATH semantics.

Fixes: 7cf97b125455 ("seccomp: Introduce addfd ioctl to seccomp user notifier")
Assisted-by: Codex:gpt-6
Signed-off-by: Cong Wang <cwang@multikernel.io>
---
 kernel/seccomp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 86cf4460d69e..4ce59be6d89f 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -1735,7 +1735,7 @@ static long seccomp_notify_addfd(struct seccomp_filter *filter,
 	if (addfd.newfd && !(addfd.flags & SECCOMP_ADDFD_FLAG_SETFD))
 		return -EINVAL;
 
-	kaddfd.file = fget(addfd.srcfd);
+	kaddfd.file = fget_raw(addfd.srcfd);
 	if (!kaddfd.file)
 		return -EBADF;
 
-- 
2.43.0