3.2.97-rc1 review patch. If anyone has any objections, please let me know.
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From: Eric Biggers ebiggers@google.com
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 [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- fs/fscache/object-list.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/fs/fscache/object-list.c +++ b/fs/fscache/object-list.c @@ -338,6 +338,13 @@ static void fscache_objlist_config(struc rcu_read_lock();
confkey = key->payload.data; + if (!confkey) { + /* key was revoked */ + rcu_read_unlock(); + key_put(key); + goto no_config; + } + buf = confkey-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--) {