[ 31/47] ipv4: fix the rcu race between free_fib_info and ip_route_output_slow

[Greg KH <gregkh@linuxfoundation.org>]

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------


From: Yanmin Zhang <yanmin_zhang@linux.intel.com>

[ Upstream commit e49cc0da7283088c5e03d475ffe2fdcb24a6d5b1 ]

We hit a kernel OOPS.

<3>[23898.789643] BUG: sleeping function called from invalid context at
/data/buildbot/workdir/ics/hardware/intel/linux-2.6/arch/x86/mm/fault.c:1103
<3>[23898.862215] in_atomic(): 0, irqs_disabled(): 0, pid: 10526, name:
Thread-6683
<4>[23898.967805] HSU serial 0000:00:05.1: 0000:00:05.2:HSU serial prevented me
to suspend...
<4>[23899.258526] Pid: 10526, comm: Thread-6683 Tainted: G        W
3.0.8-137685-ge7742f9 #1
<4>[23899.357404] HSU serial 0000:00:05.1: 0000:00:05.2:HSU serial prevented me
to suspend...
<4>[23899.904225] Call Trace:
<4>[23899.989209]  [<c1227f50>] ? pgtable_bad+0x130/0x130
<4>[23900.000416]  [<c1238c2a>] __might_sleep+0x10a/0x110
<4>[23900.007357]  [<c1228021>] do_page_fault+0xd1/0x3c0
<4>[23900.013764]  [<c18e9ba9>] ? restore_all+0xf/0xf
<4>[23900.024024]  [<c17c007b>] ? napi_complete+0x8b/0x690
<4>[23900.029297]  [<c1227f50>] ? pgtable_bad+0x130/0x130
<4>[23900.123739]  [<c1227f50>] ? pgtable_bad+0x130/0x130
<4>[23900.128955]  [<c18ea0c3>] error_code+0x5f/0x64
<4>[23900.133466]  [<c1227f50>] ? pgtable_bad+0x130/0x130
<4>[23900.138450]  [<c17f6298>] ? __ip_route_output_key+0x698/0x7c0
<4>[23900.144312]  [<c17f5f8d>] ? __ip_route_output_key+0x38d/0x7c0
<4>[23900.150730]  [<c17f63df>] ip_route_output_flow+0x1f/0x60
<4>[23900.156261]  [<c181de58>] ip4_datagram_connect+0x188/0x2b0
<4>[23900.161960]  [<c18e981f>] ? _raw_spin_unlock_bh+0x1f/0x30
<4>[23900.167834]  [<c18298d6>] inet_dgram_connect+0x36/0x80
<4>[23900.173224]  [<c14f9e88>] ? _copy_from_user+0x48/0x140
<4>[23900.178817]  [<c17ab9da>] sys_connect+0x9a/0xd0
<4>[23900.183538]  [<c132e93c>] ? alloc_file+0xdc/0x240
<4>[23900.189111]  [<c123925d>] ? sub_preempt_count+0x3d/0x50

Function free_fib_info resets nexthop_nh->nh_dev to NULL before releasing
fi. Other cpu might be accessing fi. Fixing it by delaying the releasing.

With the patch, we ran MTBF testing on Android mobile for 12 hours
and didn't trigger the issue.

Thank Eric for very detailed review/checking the issue.

Signed-off-by: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Signed-off-by: Kun Jiang <kunx.jiang@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/fib_semantics.c |   20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -142,6 +142,18 @@ const struct fib_prop fib_props[RTN_MAX
 };
 
 /* Release a nexthop info record */
+static void free_fib_info_rcu(struct rcu_head *head)
+{
+	struct fib_info *fi = container_of(head, struct fib_info, rcu);
+
+	change_nexthops(fi) {
+		if (nexthop_nh->nh_dev)
+			dev_put(nexthop_nh->nh_dev);
+	} endfor_nexthops(fi);
+
+	release_net(fi->fib_net);
+	kfree(fi);
+}
 
 void free_fib_info(struct fib_info *fi)
 {
@@ -149,14 +161,8 @@ void free_fib_info(struct fib_info *fi)
 		pr_warning("Freeing alive fib_info %p\n", fi);
 		return;
 	}
-	change_nexthops(fi) {
-		if (nexthop_nh->nh_dev)
-			dev_put(nexthop_nh->nh_dev);
-		nexthop_nh->nh_dev = NULL;
-	} endfor_nexthops(fi);
 	fib_info_cnt--;
-	release_net(fi->fib_net);
-	kfree_rcu(fi, rcu);
+	call_rcu(&fi->rcu, free_fib_info_rcu);
 }
 
 void fib_release_info(struct fib_info *fi)