stat: handle idmapped mounts

The generic_fillattr() helper fills in the basic attributes associated
with an inode. Enable it to handle idmapped mounts. If the inode is
accessed through an idmapped mount map it into the mount's user
namespace before we store the uid and gid. If the initial user namespace
is passed nothing changes so non-idmapped mounts will see identical
behavior as before.

Link: https://lore.kernel.org/r/[email protected]
Cc: Christoph Hellwig <[email protected]>
Cc: David Howells <[email protected]>
Cc: Al Viro <[email protected]>
Cc: [email protected]
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: James Morris <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/proc/root.c b/fs/proc/root.c
index 5e444d4f9717..244e4b6f15ef 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -311,7 +311,7 @@ void __init proc_root_init(void)
 static int proc_root_getattr(const struct path *path, struct kstat *stat,
 			     u32 request_mask, unsigned int query_flags)
 {
-	generic_fillattr(d_inode(path->dentry), stat);
+	generic_fillattr(&init_user_ns, d_inode(path->dentry), stat);
 	stat->nlink = proc_root.nlink + nr_processes();
 	return 0;
 }