From: Eric Biggers <ebigg...@google.com>
In proc_keys_show(), the key semaphore is not held, so the key ->flags
and ->expiry can be changed concurrently. We therefore should read them
atomically just once. Otherwise /proc/keys may show an inconsistent
state, such a key that is negative ('N') but not instantiated ('I').
Signed-off-by: Eric Biggers <ebigg...@google.com>
Signed-off-by: David Howells <dhowe...@redhat.com>
---
security/keys/proc.c | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)
diff --git a/security/keys/proc.c b/security/keys/proc.c
index 46fa0f1bfcc3..589328ed736f 100644
--- a/security/keys/proc.c
+++ b/security/keys/proc.c
@@ -179,7 +179,9 @@ static int proc_keys_show(struct seq_file *m, void *v)
struct rb_node *_p = v;
struct key *key = rb_entry(_p, struct key, serial_node);
struct timespec now;
+ time_t expiry;
unsigned long timo;
+ unsigned long flags;
key_ref_t key_ref, skey_ref;
char xbuf[16];
short state;
@@ -218,12 +220,13 @@ static int proc_keys_show(struct seq_file *m, void *v)
rcu_read_lock();
/* come up with a suitable timeout value */
- if (key->expiry == 0) {
+ expiry = READ_ONCE(key->expiry);
+ if (expiry == 0) {
memcpy(xbuf, "perm", 5);
- } else if (now.tv_sec >= key->expiry) {
+ } else if (now.tv_sec >= expiry) {
memcpy(xbuf, "expd", 5);
} else {
- timo = key->expiry - now.tv_sec;
+ timo = expiry - now.tv_sec;
if (timo < 60)
sprintf(xbuf, "%lus", timo);
@@ -239,18 +242,19 @@ static int proc_keys_show(struct seq_file *m, void *v)
state = READ_ONCE(key->state);
-#define showflag(KEY, LETTER, FLAG) \
- (test_bit(FLAG, &(KEY)->flags) ? LETTER : '-')
+#define showflag(FLAGS, LETTER, FLAG) \
+ ((FLAGS & (1 << FLAG)) ? LETTER : '-')
+ flags = READ_ONCE(key->flags);
seq_printf(m, "%08x %c%c%c%c%c%c%c %5d %4s %08x %5d %5d %-9.9s ",
key->serial,
state == KEY_IS_INSTANTIATED ? 'I' : '-',
- showflag(key, 'R', KEY_FLAG_REVOKED),
- showflag(key, 'D', KEY_FLAG_DEAD),
- showflag(key, 'Q', KEY_FLAG_IN_QUOTA),
- showflag(key, 'U', KEY_FLAG_USER_CONSTRUCT),
+ showflag(flags, 'R', KEY_FLAG_REVOKED),
+ showflag(flags, 'D', KEY_FLAG_DEAD),
+ showflag(flags, 'Q', KEY_FLAG_IN_QUOTA),
+ showflag(flags, 'U', KEY_FLAG_USER_CONSTRUCT),
state < 0 ? 'N' : '-',
- showflag(key, 'i', KEY_FLAG_INVALIDATED),
+ showflag(flags, 'i', KEY_FLAG_INVALIDATED),
refcount_read(&key->usage),
xbuf,
key->perm,
