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KEYS: load key flags and expiry time atomically in proc_keys_show() 

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.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
Eric Biggers 2017-09-27 12:50:46 -07:00 committed by David Howells
parent 9d6c8711b6
commit ab5c69f013
1 changed files with 14 additions and 10 deletions
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24
security/keys/proc.c
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@ -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 = key_read_state(key);
#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_UNINSTANTIATED ? '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,