Messages in this thread Patch in this message | | | From | Eric Biggers <> | Subject | [PATCH v2 3/6] KEYS: load key flags and expiry time atomically in key_validate() | Date | Tue, 26 Sep 2017 13:11:02 -0700 |
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From: Eric Biggers <ebiggers@google.com>
In key_validate(), load the flags and expiry time once atomically, since these can change concurrently if key_validate() is called without the key semaphore held. And we don't want to get inconsistent results if a variable is referenced multiple times. For example, key->expiry was referenced in both 'if (key->expiry)' and in 'if (now.tv_sec >= key->expiry)', making it theoretically possible to see a spurious EKEYEXPIRED while the expiration time was being removed, i.e. set to 0.
Signed-off-by: Eric Biggers <ebiggers@google.com> --- security/keys/permission.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/security/keys/permission.c b/security/keys/permission.c index 732cc0beffdf..a72b4dd70c8a 100644 --- a/security/keys/permission.c +++ b/security/keys/permission.c @@ -88,7 +88,8 @@ EXPORT_SYMBOL(key_task_permission); */ int key_validate(const struct key *key) { - unsigned long flags = key->flags; + unsigned long flags = READ_ONCE(key->flags); + time_t expiry = READ_ONCE(key->expiry); if (flags & (1 << KEY_FLAG_INVALIDATED)) return -ENOKEY; @@ -99,9 +100,9 @@ int key_validate(const struct key *key) return -EKEYREVOKED; /* check it hasn't expired */ - if (key->expiry) { + if (expiry) { struct timespec now = current_kernel_time(); - if (now.tv_sec >= key->expiry) + if (now.tv_sec >= expiry) return -EKEYEXPIRED; } -- 2.14.1.992.g2c7b836f3a-goog
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