[PATCH] ceph: use the mount idmap for the owner checks in the SET_LAYOUT ioctls

[Zhan Xusheng <zhanxusheng1024@gmail.com>]

From: Zhan Xusheng <zhanxusheng@xiaomi.com>

ceph_ioctl_set_layout() and ceph_ioctl_set_layout_policy() call
inode_owner_or_capable() with &nop_mnt_idmap instead of the idmap of the
mount the ioctl was issued on.

CephFS supports idmapped mounts (FS_ALLOW_IDMAP), so on such a mount this
compares the caller's fsuid against the unmapped on-disk owner rather than
the mapped owner: the actual owner can be wrongly denied with -EACCES and
an unrelated caller wrongly allowed.  Both functions already have the
struct file, so use file_mnt_idmap(file) instead.

Fixes: cee38bbf5556 ("ceph: add owner/capability checks for CEPH_IOC_SET_LAYOUT*")
Cc: stable@vger.kernel.org
Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
---
 fs/ceph/ioctl.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ceph/ioctl.c b/fs/ceph/ioctl.c
index de07f19b0caa..12cb50e0a166 100644
--- a/fs/ceph/ioctl.c
+++ b/fs/ceph/ioctl.c
@@ -72,7 +72,7 @@ static long ceph_ioctl_set_layout(struct file *file, void __user *arg)
 	struct ceph_ioctl_layout nl;
 	int err;
 
-	if (!inode_owner_or_capable(&nop_mnt_idmap, inode))
+	if (!inode_owner_or_capable(file_mnt_idmap(file), inode))
 		return -EACCES;
 
 	if (copy_from_user(&l, arg, sizeof(l)))
@@ -145,7 +145,7 @@ static long ceph_ioctl_set_layout_policy (struct file *file, void __user *arg)
 	int err;
 	struct ceph_mds_client *mdsc = ceph_sb_to_fs_client(inode->i_sb)->mdsc;
 
-	if (!inode_owner_or_capable(&nop_mnt_idmap, inode))
+	if (!inode_owner_or_capable(file_mnt_idmap(file), inode))
 		return -EACCES;
 
 	/* copy and validate */
-- 
2.43.0