Commit b59ec78c authored by David Howells's avatar David Howells Committed by James Morris
Browse files

keys: don't need to use RCU in keyring_read() as semaphore is held

keyring_read() doesn't need to use rcu_dereference() to access the keyring
payload as the caller holds the key semaphore to prevent modifications
from happening whilst the data is read out.

This should solve the following warning:

[ INFO: suspicious rcu_dereference_check() usage. ]
security/keys/keyring.c:204 invoked rcu_dereference_check() without protection!

other info that might help us debug this:

rcu_scheduler_active = 1, debug_locks = 0
1 lock held by keyctl/2144:
 #0:  (&key->sem){+++++.}, at: [<ffffffff81177f7c>] keyctl_read_key+0x9c/0xcf

stack backtrace:
Pid: 2144, comm: keyctl Not tainted 2.6.34-rc2-cachefs #113
Call Trace:
 [<ffffffff8105121f>] lockdep_rcu_dereference+0xaa/0xb2
 [<ffffffff811762d5>] keyring_read+0x4d/0xe7
 [<ffffffff81177f8c>] keyctl_read_key+0xac/0xcf
 [<ffffffff811788d4>] sys_keyctl+0x75/0xb9
 [<ffffffff81001eeb>] system_call_fastpath+0x16/0x1b
Signed-off-by: default avatarDavid Howells <>
Cc: Herbert Xu <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarJames Morris <>
parent b91ce4d1
......@@ -201,7 +201,7 @@ static long keyring_read(const struct key *keyring,
int loop, ret;
ret = 0;
klist = rcu_dereference(keyring->payload.subscriptions);
klist = keyring->payload.subscriptions;
if (klist) {
/* calculate how much data we could return */
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