63 lines
2.6 KiB
Diff
63 lines
2.6 KiB
Diff
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From 950eaaca681c44aab87a46225c9e44f902c080aa Mon Sep 17 00:00:00 2001
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From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Date: Tue, 31 Aug 2010 17:00:18 -0700
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Subject: pid: make setpgid() system call use RCU read-side critical section
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Git-commit: 950eaaca681c44aab87a46225c9e44f902c080aa
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Patch-mainline: yes
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References: bnc#639728
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[ 23.584719]
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[ 23.584720] ===================================================
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[ 23.585059] [ INFO: suspicious rcu_dereference_check() usage. ]
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[ 23.585176] ---------------------------------------------------
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[ 23.585176] kernel/pid.c:419 invoked rcu_dereference_check() without protection!
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[ 23.585176]
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[ 23.585176] other info that might help us debug this:
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[ 23.585176]
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[ 23.585176]
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[ 23.585176] rcu_scheduler_active = 1, debug_locks = 1
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[ 23.585176] 1 lock held by rc.sysinit/728:
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[ 23.585176] #0: (tasklist_lock){.+.+..}, at: [<ffffffff8104771f>] sys_setpgid+0x5f/0x193
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[ 23.585176]
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[ 23.585176] stack backtrace:
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[ 23.585176] Pid: 728, comm: rc.sysinit Not tainted 2.6.36-rc2 #2
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[ 23.585176] Call Trace:
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[ 23.585176] [<ffffffff8105b436>] lockdep_rcu_dereference+0x99/0xa2
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[ 23.585176] [<ffffffff8104c324>] find_task_by_pid_ns+0x50/0x6a
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[ 23.585176] [<ffffffff8104c35b>] find_task_by_vpid+0x1d/0x1f
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[ 23.585176] [<ffffffff81047727>] sys_setpgid+0x67/0x193
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[ 23.585176] [<ffffffff810029eb>] system_call_fastpath+0x16/0x1b
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[ 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
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It turns out that the setpgid() system call fails to enter an RCU
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read-side critical section before doing a PID-to-task_struct translation.
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This commit therefore does rcu_read_lock() before the translation, and
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also does rcu_read_unlock() after the last use of the returned pointer.
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Reported-by: Andrew Morton <akpm@linux-foundation.org>
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Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Acked-by: David Howells <dhowells@redhat.com>
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Signed-off-by: Jiri Slaby <jslaby@suse.cz>
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---
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kernel/sys.c | 2 ++
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1 file changed, 2 insertions(+)
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--- a/kernel/sys.c
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+++ b/kernel/sys.c
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@@ -962,6 +962,7 @@ SYSCALL_DEFINE2(setpgid, pid_t, pid, pid
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pgid = pid;
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if (pgid < 0)
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return -EINVAL;
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+ rcu_read_lock();
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/* From this point forward we keep holding onto the tasklist lock
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* so that our parent does not change from under us. -DaveM
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@@ -1015,6 +1016,7 @@ SYSCALL_DEFINE2(setpgid, pid_t, pid, pid
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out:
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/* All paths lead to here, thus we are safe. -DaveM */
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write_unlock_irq(&tasklist_lock);
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+ rcu_read_unlock();
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return err;
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}
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