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author | 2017-06-08 14:47:41 +0100 | |
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committer | 2017-06-09 13:29:50 +1000 | |
commit | 92347cfd62c174ab91ad97dd4bfbaa1d4aa28e67 (patch) | |
tree | b3bc051f940ef773d5fb6e01401f70700ef8b875 | |
parent | KEYS: Convert KEYCTL_DH_COMPUTE to use the crypto KPP API (diff) | |
download | linux-92347cfd62c174ab91ad97dd4bfbaa1d4aa28e67.tar.gz linux-92347cfd62c174ab91ad97dd4bfbaa1d4aa28e67.tar.bz2 linux-92347cfd62c174ab91ad97dd4bfbaa1d4aa28e67.zip |
KEYS: fix refcount_inc() on zero
If a key's refcount is dropped to zero between key_lookup() peeking at
the refcount and subsequently attempting to increment it, refcount_inc()
will see a zero refcount. Here, refcount_inc() will WARN_ONCE(), and
will *not* increment the refcount, which will remain zero.
Once key_lookup() drops key_serial_lock, it is possible for the key to
be freed behind our back.
This patch uses refcount_inc_not_zero() to perform the peek and increment
atomically.
Fixes: fff292914d3a2f1e ("security, keys: convert key.usage from atomic_t to refcount_t")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: David Windsor <dwindsor@gmail.com>
Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: Hans Liljestrand <ishkamiel@gmail.com>
Cc: James Morris <james.l.morris@oracle.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: James Morris <james.l.morris@oracle.com>
-rw-r--r-- | security/keys/key.c | 11 |
1 files changed, 4 insertions, 7 deletions
diff --git a/security/keys/key.c b/security/keys/key.c index cbae368c0e57..83da68d98b40 100644 --- a/security/keys/key.c +++ b/security/keys/key.c @@ -660,14 +660,11 @@ not_found: goto error; found: - /* pretend it doesn't exist if it is awaiting deletion */ - if (refcount_read(&key->usage) == 0) - goto not_found; - - /* this races with key_put(), but that doesn't matter since key_put() - * doesn't actually change the key + /* A key is allowed to be looked up only if someone still owns a + * reference to it - otherwise it's awaiting the gc. */ - __key_get(key); + if (!refcount_inc_not_zero(&key->usage)) + goto not_found; error: spin_unlock(&key_serial_lock); |