Messages in this thread Patch in this message | | | From | Eric Biggers <> | Subject | [PATCH v2 5/6] KEYS: load key flags and expiry time atomically in proc_keys_show() | Date | Tue, 26 Sep 2017 13:11:04 -0700 |
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From: Eric Biggers <ebiggers@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 <ebiggers@google.com> --- security/keys/proc.c | 28 ++++++++++++++++------------ 1 file changed, 16 insertions(+), 12 deletions(-)
diff --git a/security/keys/proc.c b/security/keys/proc.c index de834309d100..a038069ac46a 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]; int rc; @@ -217,12 +219,13 @@ 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); @@ -236,18 +239,19 @@ static int proc_keys_show(struct seq_file *m, void *v) sprintf(xbuf, "%luw", timo / (60*60*24*7)); } -#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, - showflag(key, 'I', KEY_FLAG_INSTANTIATED), - 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(key, 'N', KEY_FLAG_NEGATIVE), - showflag(key, 'i', KEY_FLAG_INVALIDATED), + showflag(flags, 'I', KEY_FLAG_INSTANTIATED), + 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), + showflag(flags, 'N', KEY_FLAG_NEGATIVE), + showflag(flags, 'i', KEY_FLAG_INVALIDATED), refcount_read(&key->usage), xbuf, key->perm, -- 2.14.1.992.g2c7b836f3a-goog
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