[PATCH 5.15 053/476] afs: Hide silly-rename files from userspace

[Greg Kroah-Hartman]

5.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Howells <dhowells at redhat.com>

[ Upstream commit 57e9d49c54528c49b8bffe6d99d782ea051ea534 ]

There appears to be a race between silly-rename files being created/removed
and various userspace tools iterating over the contents of a directory,
leading to such errors as:

	find: './kernel/.tmp_cpio_dir/include/dt-bindings/reset/.__afs2080': No such file or directory
	tar: ./include/linux/greybus/.__afs3C95: File removed before we read it

when building a kernel.

Fix afs_readdir() so that it doesn't return .__afsXXXX silly-rename files
to userspace.  This doesn't stop them being looked up directly by name as
we need to be able to look them up from within the kernel as part of the
silly-rename algorithm.

Fixes: 79ddbfa500b3 ("afs: Implement sillyrename for unlink and rename")
Signed-off-by: David Howells <dhowells at redhat.com>
cc: Marc Dionne <marc.dionne at auristor.com>
cc: linux-afs at lists.infradead.org
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 fs/afs/dir.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index cec18f9f8bd7..106426de5027 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -492,6 +492,14 @@ static int afs_dir_iterate_block(struct afs_vnode *dvnode,
 			continue;
 		}
 
+		/* Don't expose silly rename entries to userspace. */
+		if (nlen > 6 &&
+		    dire->u.name[0] == '.' &&
+		    ctx->actor != afs_lookup_filldir &&
+		    ctx->actor != afs_lookup_one_filldir &&
+		    memcmp(dire->u.name, ".__afs", 6) == 0)
+			continue;
+
 		/* found the next entry */
 		if (!dir_emit(ctx, dire->u.name, nlen,
 			      ntohl(dire->u.vnode),
-- 
2.43.0