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Subject[patch 20/60] ipvs: Fix possible deadlock in estimator code
2.6.26-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Sven Wegener <sven.wegener@stealer.net>

commit 8ab19ea36c5c5340ff598e4d15fc084eb65671dc upstream

There is a slight chance for a deadlock in the estimator code. We can't call
del_timer_sync() while holding our lock, as the timer might be active and
spinning for the lock on another cpu. Work around this issue by using
try_to_del_timer_sync() and releasing the lock. We could actually delete the
timer outside of our lock, as the add and kill functions are only every called
from userspace via [gs]etsockopt() and are serialized by a mutex, but better
make this explicit.

Signed-off-by: Sven Wegener <sven.wegener@stealer.net>
Acked-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
net/ipv4/ipvs/ip_vs_est.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

--- a/net/ipv4/ipvs/ip_vs_est.c
+++ b/net/ipv4/ipvs/ip_vs_est.c
@@ -172,8 +172,11 @@ void ip_vs_kill_estimator(struct ip_vs_s
kfree(est);
killed++;
}
- if (killed && est_list == NULL)
- del_timer_sync(&est_timer);
+ while (killed && !est_list && try_to_del_timer_sync(&est_timer) < 0) {
+ write_unlock_bh(&est_lock);
+ cpu_relax();
+ write_lock_bh(&est_lock);
+ }
write_unlock_bh(&est_lock);
}

--


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