Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.13 63/85] FS-Cache: fix dereference of NULL user_key_payload | Date | Tue, 24 Oct 2017 15:07:37 +0200 |
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4.13-stable 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- fs/fscache/object-list.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/fs/fscache/object-list.c +++ b/fs/fscache/object-list.c @@ -330,6 +330,13 @@ static void fscache_objlist_config(struc rcu_read_lock(); confkey = user_key_payload_rcu(key); + if (!confkey) { + /* key was revoked */ + rcu_read_unlock(); + key_put(key); + goto no_config; + } + buf = confkey-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--) {
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