summaryrefslogtreecommitdiff
path: root/kernel
diff options
context:
space:
mode:
authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-08-31 17:00:18 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2011-03-21 12:45:45 -0700
commit527a95060a52006117803e36ac63911540fe0cf3 (patch)
tree90b5058d1edf1e9eebf3e59843afc062bac30015 /kernel
parentd941cd42c4c5056eaffaa35fb30480effc9a5278 (diff)
pid: make setpgid() system call use RCU read-side critical section
commit 950eaaca681c44aab87a46225c9e44f902c080aa upstream. [ 23.584719] [ 23.584720] =================================================== [ 23.585059] [ INFO: suspicious rcu_dereference_check() usage. ] [ 23.585176] --------------------------------------------------- [ 23.585176] kernel/pid.c:419 invoked rcu_dereference_check() without protection! [ 23.585176] [ 23.585176] other info that might help us debug this: [ 23.585176] [ 23.585176] [ 23.585176] rcu_scheduler_active = 1, debug_locks = 1 [ 23.585176] 1 lock held by rc.sysinit/728: [ 23.585176] #0: (tasklist_lock){.+.+..}, at: [<ffffffff8104771f>] sys_setpgid+0x5f/0x193 [ 23.585176] [ 23.585176] stack backtrace: [ 23.585176] Pid: 728, comm: rc.sysinit Not tainted 2.6.36-rc2 #2 [ 23.585176] Call Trace: [ 23.585176] [<ffffffff8105b436>] lockdep_rcu_dereference+0x99/0xa2 [ 23.585176] [<ffffffff8104c324>] find_task_by_pid_ns+0x50/0x6a [ 23.585176] [<ffffffff8104c35b>] find_task_by_vpid+0x1d/0x1f [ 23.585176] [<ffffffff81047727>] sys_setpgid+0x67/0x193 [ 23.585176] [<ffffffff810029eb>] system_call_fastpath+0x16/0x1b [ 24.959669] type=1400 audit(1282938522.956:4): avc: denied { module_request } for pid=766 comm="hwclock" kmod="char-major-10-135" scontext=system_u:system_r:hwclock_t:s0 tcontext=system_u:system_r:kernel_t:s0 tclas It turns out that the setpgid() system call fails to enter an RCU read-side critical section before doing a PID-to-task_struct translation. This commit therefore does rcu_read_lock() before the translation, and also does rcu_read_unlock() after the last use of the returned pointer. Reported-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: David Howells <dhowells@redhat.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sys.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/sys.c b/kernel/sys.c
index 18bde979f346..3868b7ba9302 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -966,6 +966,7 @@ SYSCALL_DEFINE2(setpgid, pid_t, pid, pid_t, pgid)
pgid = pid;
if (pgid < 0)
return -EINVAL;
+ rcu_read_lock();
/* From this point forward we keep holding onto the tasklist lock
* so that our parent does not change from under us. -DaveM
@@ -1019,6 +1020,7 @@ SYSCALL_DEFINE2(setpgid, pid_t, pid, pid_t, pgid)
out:
/* All paths lead to here, thus we are safe. -DaveM */
write_unlock_irq(&tasklist_lock);
+ rcu_read_unlock();
return err;
}