keys, dns: Allow key types (eg. DNS) to be reclaimed immediately on expiry

If a key has an expiration time, then when that time passes, the key is
left around for a certain amount of time before being collected (5 mins by
default) so that EKEYEXPIRED can be returned instead of ENOKEY.  This is a
problem for DNS keys because we want to redo the DNS lookup immediately at
that point.

Fix this by allowing key types to be marked such that keys of that type
don't have this extra period, but are reclaimed as soon as they expire and
turn this on for dns_resolver-type keys.  To make this easier to handle,
key->expiry is changed to be permanent if TIME64_MAX rather than 0.

Furthermore, give such new-style negative DNS results a 1s default expiry
if no other expiry time is set rather than allowing it to stick around
indefinitely.  This shouldn't be zero as ls will follow a failing stat call
immediately with a second with AT_SYMLINK_NOFOLLOW added.

Fixes: 1a4240f4764a ("DNS: Separate out CIFS DNS Resolver code")
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Markus Suvanto <markus.suvanto@gmail.com>
cc: Wang Lei <wang840925@gmail.com>
cc: Jeff Layton <jlayton@redhat.com>
cc: Steve French <smfrench@gmail.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Jarkko Sakkinen <jarkko@kernel.org>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: linux-afs@lists.infradead.org
cc: linux-cifs@vger.kernel.org
cc: linux-nfs@vger.kernel.org
cc: ceph-devel@vger.kernel.org
cc: keyrings@vger.kernel.org
cc: netdev@vger.kernel.org

diff --git a/include/linux/key-type.h b/include/linux/key-type.h
index 7d985a1dfe4af9e4fa38122260f44cfe336b206e..5caf3ce823733ab510f53d8dfa4b25cc150dbae4 100644 (file)
--- a/include/linux/key-type.h
+++ b/include/linux/key-type.h
@@ -73,6 +73,7 @@ struct key_type {
 
        unsigned int flags;
 #define KEY_TYPE_NET_DOMAIN    0x00000001 /* Keys of this type have a net namespace domain */
+#define KEY_TYPE_INSTANT_REAP  0x00000002 /* Keys of this type don't have a delay after expiring */
 
        /* vet a description */
        int (*vet_description)(const char *description);

diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
index 01e54b46ae0b9786730a79401cb58762896d0b50..2a6d363763a2bcf287708db50c9fba89486071e0 100644 (file)
--- a/net/dns_resolver/dns_key.c
+++ b/net/dns_resolver/dns_key.c
@@ -91,6 +91,7 @@ const struct cred *dns_resolver_cache;
 static int
 dns_resolver_preparse(struct key_preparsed_payload *prep)
 {
+       const struct dns_server_list_v1_header *v1;
        const struct dns_payload_header *bin;
        struct user_key_payload *upayload;
        unsigned long derrno;
@@ -122,6 +123,13 @@ dns_resolver_preparse(struct key_preparsed_payload *prep)
                        return -EINVAL;
                }
 
+               v1 = (const struct dns_server_list_v1_header *)bin;
+               if ((v1->status != DNS_LOOKUP_GOOD &&
+                    v1->status != DNS_LOOKUP_GOOD_WITH_BAD)) {
+                       if (prep->expiry == TIME64_MAX)
+                               prep->expiry = ktime_get_real_seconds() + 1;
+               }
+
                result_len = datalen;
                goto store_result;
        }
@@ -314,7 +322,7 @@ static long dns_resolver_read(const struct key *key,
 
 struct key_type key_type_dns_resolver = {
        .name           = "dns_resolver",
-       .flags          = KEY_TYPE_NET_DOMAIN,
+       .flags          = KEY_TYPE_NET_DOMAIN | KEY_TYPE_INSTANT_REAP,
        .preparse       = dns_resolver_preparse,
        .free_preparse  = dns_resolver_free_preparse,
        .instantiate    = generic_key_instantiate,

diff --git a/security/keys/gc.c b/security/keys/gc.c
index 3c90807476eb0e293a85940daff55c30bf636169..eaddaceda14eab077512f75081f102cf00157566 100644 (file)
--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -66,6 +66,19 @@ void key_schedule_gc(time64_t gc_at)
        }
 }
 
+/*
+ * Set the expiration time on a key.
+ */
+void key_set_expiry(struct key *key, time64_t expiry)
+{
+       key->expiry = expiry;
+       if (expiry != TIME64_MAX) {
+               if (!(key->type->flags & KEY_TYPE_INSTANT_REAP))
+                       expiry += key_gc_delay;
+               key_schedule_gc(expiry);
+       }
+}
+
 /*
  * Schedule a dead links collection run.
  */
@@ -176,7 +189,6 @@ static void key_garbage_collector(struct work_struct *work)
        static u8 gc_state;             /* Internal persistent state */
 #define KEY_GC_REAP_AGAIN      0x01    /* - Need another cycle */
 #define KEY_GC_REAPING_LINKS   0x02    /* - We need to reap links */
-#define KEY_GC_SET_TIMER       0x04    /* - We need to restart the timer */
 #define KEY_GC_REAPING_DEAD_1  0x10    /* - We need to mark dead keys */
 #define KEY_GC_REAPING_DEAD_2  0x20    /* - We need to reap dead key links */
 #define KEY_GC_REAPING_DEAD_3  0x40    /* - We need to reap dead keys */
@@ -184,21 +196,17 @@ static void key_garbage_collector(struct work_struct *work)
 
        struct rb_node *cursor;
        struct key *key;
-       time64_t new_timer, limit;
+       time64_t new_timer, limit, expiry;
 
        kenter("[%lx,%x]", key_gc_flags, gc_state);
 
        limit = ktime_get_real_seconds();
-       if (limit > key_gc_delay)
-               limit -= key_gc_delay;
-       else
-               limit = key_gc_delay;
 
        /* Work out what we're going to be doing in this pass */
        gc_state &= KEY_GC_REAPING_DEAD_1 | KEY_GC_REAPING_DEAD_2;
        gc_state <<= 1;
        if (test_and_clear_bit(KEY_GC_KEY_EXPIRED, &key_gc_flags))
-               gc_state |= KEY_GC_REAPING_LINKS | KEY_GC_SET_TIMER;
+               gc_state |= KEY_GC_REAPING_LINKS;
 
        if (test_and_clear_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags))
                gc_state |= KEY_GC_REAPING_DEAD_1;
@@ -233,8 +241,11 @@ continue_scanning:
                        }
                }
 
-               if (gc_state & KEY_GC_SET_TIMER) {
-                       if (key->expiry > limit && key->expiry < new_timer) {
+               expiry = key->expiry;
+               if (expiry != TIME64_MAX) {
+                       if (!(key->type->flags & KEY_TYPE_INSTANT_REAP))
+                               expiry += key_gc_delay;
+                       if (expiry > limit && expiry < new_timer) {
                                kdebug("will expire %x in %lld",
                                       key_serial(key), key->expiry - limit);
                                new_timer = key->expiry;
@@ -276,7 +287,7 @@ maybe_resched:
         */
        kdebug("pass complete");
 
-       if (gc_state & KEY_GC_SET_TIMER && new_timer != (time64_t)TIME64_MAX) {
+       if (new_timer != TIME64_MAX) {
                new_timer += key_gc_delay;
                key_schedule_gc(new_timer);
        }

diff --git a/security/keys/internal.h b/security/keys/internal.h
index 471cf36dedc0268de02e2ca8dd3ec2fe9f316ed1..2cffa6dc82557b00671f6e473d459b437a902acb 100644 (file)
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -167,6 +167,7 @@ extern unsigned key_gc_delay;
 extern void keyring_gc(struct key *keyring, time64_t limit);
 extern void keyring_restriction_gc(struct key *keyring,
                                   struct key_type *dead_type);
+void key_set_expiry(struct key *key, time64_t expiry);
 extern void key_schedule_gc(time64_t gc_at);
 extern void key_schedule_gc_links(void);
 extern void key_gc_keytype(struct key_type *ktype);
@@ -215,10 +216,18 @@ extern struct key *key_get_instantiation_authkey(key_serial_t target_id);
  */
 static inline bool key_is_dead(const struct key *key, time64_t limit)
 {
+       time64_t expiry = key->expiry;
+
+       if (expiry != TIME64_MAX) {
+               if (!(key->type->flags & KEY_TYPE_INSTANT_REAP))
+                       expiry += key_gc_delay;
+               if (expiry <= limit)
+                       return true;
+       }
+
        return
                key->flags & ((1 << KEY_FLAG_DEAD) |
                              (1 << KEY_FLAG_INVALIDATED)) ||
-               (key->expiry > 0 && key->expiry <= limit) ||
                key->domain_tag->removed;
 }
 

diff --git a/security/keys/key.c b/security/keys/key.c
index 0260a1902922eb47aa79e94437239f6687c1c86b..5b10641debd54910bbb4f2872ea6039a0471bcf5 100644 (file)
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -294,6 +294,7 @@ struct key *key_alloc(struct key_type *type, const char *desc,
        key->uid = uid;
        key->gid = gid;
        key->perm = perm;
+       key->expiry = TIME64_MAX;
        key->restrict_link = restrict_link;
        key->last_used_at = ktime_get_real_seconds();
 
@@ -463,10 +464,7 @@ static int __key_instantiate_and_link(struct key *key,
                        if (authkey)
                                key_invalidate(authkey);
 
-                       if (prep->expiry != TIME64_MAX) {
-                               key->expiry = prep->expiry;
-                               key_schedule_gc(prep->expiry + key_gc_delay);
-                       }
+                       key_set_expiry(key, prep->expiry);
                }
        }
 
@@ -606,8 +604,7 @@ int key_reject_and_link(struct key *key,
                atomic_inc(&key->user->nikeys);
                mark_key_instantiated(key, -error);
                notify_key(key, NOTIFY_KEY_INSTANTIATED, -error);
-               key->expiry = ktime_get_real_seconds() + timeout;
-               key_schedule_gc(key->expiry + key_gc_delay);
+               key_set_expiry(key, ktime_get_real_seconds() + timeout);
 
                if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
                        awaken = 1;
@@ -723,16 +720,14 @@ found_kernel_type:
 
 void key_set_timeout(struct key *key, unsigned timeout)
 {
-       time64_t expiry = 0;
+       time64_t expiry = TIME64_MAX;
 
        /* make the changes with the locks held to prevent races */
        down_write(&key->sem);
 
        if (timeout > 0)
                expiry = ktime_get_real_seconds() + timeout;
-
-       key->expiry = expiry;
-       key_schedule_gc(key->expiry + key_gc_delay);
+       key_set_expiry(key, expiry);
 
        up_write(&key->sem);
 }

diff --git a/security/keys/proc.c b/security/keys/proc.c
index d0cde6685627f2ab6d3cc0d6919b7e8a50c10dd0..4f4e2c1824f18bd480554661f6f2f2d67c9bce51 100644 (file)
--- a/security/keys/proc.c
+++ b/security/keys/proc.c
@@ -198,7 +198,7 @@ static int proc_keys_show(struct seq_file *m, void *v)
 
        /* come up with a suitable timeout value */
        expiry = READ_ONCE(key->expiry);
-       if (expiry == 0) {
+       if (expiry == TIME64_MAX) {
                memcpy(xbuf, "perm", 5);
        } else if (now >= expiry) {
                memcpy(xbuf, "expd", 5);