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authorEric Biggers <ebiggers@google.com>2017-10-09 12:40:00 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-10-27 10:23:18 +0200
commitaa3a0a70bdb8745864e41fca5f7722dfb3908d85 (patch)
parent1bb1d4252d1ede47afea054979fb9d95fc891743 (diff)
FS-Cache: fix dereference of NULL user_key_payload
commit d124b2c53c7bee6569d2a2d0b18b4a1afde00134 upstream. 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> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 7 insertions, 0 deletions
diff --git a/fs/fscache/object-list.c b/fs/fscache/object-list.c
index 6b028b7c4250..926580a85153 100644
--- a/fs/fscache/object-list.c
+++ b/fs/fscache/object-list.c
@@ -330,6 +330,13 @@ static void fscache_objlist_config(struct fscache_objlist_data *data)
confkey = user_key_payload(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+ /* key was revoked */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--) {