[PATCH 5.9 231/255] NFSv4.2: fix failure to unregister shrinker

Greg Kroah-Hartman
2020-11-17T13:43:34Z

From: J. Bruce Fields <bfields@redhat.com>

commit 70438afbf17e5194dd607dd17759560a363b7bb4 upstream.

We forgot to unregister the nfs4_xattr_large_entry_shrinker.

That leaves the global list of shrinkers corrupted after unload of the
nfs module, after which possibly unrelated code that calls
register_shrinker() or unregister_shrinker() gets a BUG() with
"supervisor write access in kernel mode".

And similarly for the nfs4_xattr_large_entry_lru.

Reported-by: Kris Karas <bugs-a17@moonlit-rail.com>
Tested-By: Kris Karas <bugs-a17@moonlit-rail.com>
Fixes: 95ad37f90c33 "NFSv4.2: add client side xattr caching."
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
CC: stable@vger.kernel.org
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/nfs/nfs42xattr.c | 2 ++
1 file changed, 2 insertions(+)

--- a/fs/nfs/nfs42xattr.c
+++ b/fs/nfs/nfs42xattr.c
@@ -1048,8 +1048,10 @@ out4:

void nfs4_xattr_cache_exit(void)
{
+ unregister_shrinker(&nfs4_xattr_large_entry_shrinker);
unregister_shrinker(&nfs4_xattr_entry_shrinker);
unregister_shrinker(&nfs4_xattr_cache_shrinker);
+ list_lru_destroy(&nfs4_xattr_large_entry_lru);
list_lru_destroy(&nfs4_xattr_entry_lru);
list_lru_destroy(&nfs4_xattr_cache_lru);
kmem_cache_destroy(nfs4_xattr_cache_cachep);