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authorEric Biggers <ebiggers@google.com>2017-10-09 12:40:00 -0700
committerDavid Howells <dhowells@redhat.com>2017-10-12 17:16:40 +0100
commitd124b2c53c7bee6569d2a2d0b18b4a1afde00134 (patch)
treebf9b812982023ef6893d58c1a8bdc8f52bd173fc
parent13923d0865ca96312197962522e88bc0aedccd74 (diff)
FS-Cache: fix dereference of NULL user_key_payload
When the file /proc/fs/fscache/objects (available with CONFIG_FSCACHE_OBJECT_LIST=y) is opened, we request a user key with description "fscache:objlist", then access its payload. However, a revoked key has a NULL payload, and we failed to check for this. request_key() *does* skip revoked keys, but there is still a window where the key can be revoked before we access its payload. Fix it by checking for a NULL payload, treating it like a key which was already revoked at the time it was requested. Fixes: 4fbf4291aa15 ("FS-Cache: Allow the current state of all objects to be dumped") Reviewed-by: James Morris <james.l.morris@oracle.com> Cc: <stable@vger.kernel.org> [v2.6.32+] Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: David Howells <dhowells@redhat.com>
-rw-r--r--fs/fscache/object-list.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/fs/fscache/object-list.c b/fs/fscache/object-list.c
index b5ab06fabc60..0438d4cd91ef 100644
--- a/fs/fscache/object-list.c
+++ b/fs/fscache/object-list.c
@@ -331,6 +331,13 @@ static void fscache_objlist_config(struct fscache_objlist_data *data)
rcu_read_lock();
confkey = user_key_payload_rcu(key);
+ if (!confkey) {
+ /* key was revoked */
+ rcu_read_unlock();
+ key_put(key);
+ goto no_config;
+ }
+
buf = confkey->data;
for (len = confkey->datalen - 1; len >= 0; len--) {