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authorDavid Howells <dhowells@redhat.com>2023-03-14 15:15:18 +0000
committerDavid Howells <dhowells@redhat.com>2023-03-21 16:22:40 +0000
commit47f9e4c924025c5be87959d3335e66fcbb7f6b5c (patch)
tree4197191eaf26c2db1c5eb6463e437b887977b4ba /security
parentfc89d7fb499b0162e081f434d45e8d1b47e82ece (diff)
keys: Do not cache key in task struct if key is requested from kernel thread
The key which gets cached in task structure from a kernel thread does not get invalidated even after expiry. Due to which, a new key request from kernel thread will be served with the cached key if it's present in task struct irrespective of the key validity. The change is to not cache key in task_struct when key requested from kernel thread so that kernel thread gets a valid key on every key request. The problem has been seen with the cifs module doing DNS lookups from a kernel thread and the results getting pinned by being attached to that kernel thread's cache - and thus not something that can be easily got rid of. The cache would ordinarily be cleared by notify-resume, but kernel threads don't do that. This isn't seen with AFS because AFS is doing request_key() within the kernel half of a user thread - which will do notify-resume. Fixes: 7743c48e54ee ("keys: Cache result of request_key*() temporarily in task_struct") Signed-off-by: Bharath SM <bharathsm@microsoft.com> Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> cc: Shyam Prasad N <nspmangalore@gmail.com> cc: Steve French <smfrench@gmail.com> cc: keyrings@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/CAGypqWw951d=zYRbdgNR4snUDvJhWL=q3=WOyh7HhSJupjz2vA@mail.gmail.com/
Diffstat (limited to 'security')
-rw-r--r--security/keys/request_key.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 2da4404276f0..07a0ef2baacd 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -38,9 +38,12 @@ static void cache_requested_key(struct key *key)
#ifdef CONFIG_KEYS_REQUEST_CACHE
struct task_struct *t = current;
- key_put(t->cached_requested_key);
- t->cached_requested_key = key_get(key);
- set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
+ /* Do not cache key if it is a kernel thread */
+ if (!(t->flags & PF_KTHREAD)) {
+ key_put(t->cached_requested_key);
+ t->cached_requested_key = key_get(key);
+ set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
+ }
#endif
}