[PATCH -stable 3.18, backport] ipmr: fix possible race resulting from improper usage of IP_INC_STATS_BH() in preemptible context.

[PATCH -stable 3.18, backport] ipmr: fix possible race resulting from improper usage of IP_INC_STATS_BH() in preemptible context.

[Ani Sinha]

[ Upstream commit 44f49dd8b5a606870a1f2 ] 

Fixes the following kernel BUG :

BUG: using __this_cpu_add() in preemptible [00000000] code: bash/2758
caller is __this_cpu_preempt_check+0x13/0x15
CPU: 0 PID: 2758 Comm: bash Tainted: P           O   3.18.19 #2
 ffffffff8170eaca ffff880110d1b788 ffffffff81482b2a 0000000000000000
 0000000000000000 ffff880110d1b7b8 ffffffff812010ae ffff880007cab800
 ffff88001a060800 ffff88013a899108 ffff880108b84240 ffff880110d1b7c8
Call Trace:
[<ffffffff81482b2a>] dump_stack+0x52/0x80
[<ffffffff812010ae>] check_preemption_disabled+0xce/0xe1
[<ffffffff812010d4>] __this_cpu_preempt_check+0x13/0x15
[<ffffffff81419d60>] ipmr_queue_xmit+0x647/0x70c
[<ffffffff8141a154>] ip_mr_forward+0x32f/0x34e
[<ffffffff8141af76>] ip_mroute_setsockopt+0xe03/0x108c
[<ffffffff810553fc>] ? get_parent_ip+0x11/0x42
[<ffffffff810e6974>] ? pollwake+0x4d/0x51
[<ffffffff81058ac0>] ? default_wake_function+0x0/0xf
[<ffffffff810553fc>] ? get_parent_ip+0x11/0x42
[<ffffffff810613d9>] ? __wake_up_common+0x45/0x77
[<ffffffff81486ea9>] ? _raw_spin_unlock_irqrestore+0x1d/0x32
[<ffffffff810618bc>] ? __wake_up_sync_key+0x4a/0x53
[<ffffffff8139a519>] ? sock_def_readable+0x71/0x75
[<ffffffff813dd226>] do_ip_setsockopt+0x9d/0xb55
[<ffffffff81429818>] ? unix_seqpacket_sendmsg+0x3f/0x41
[<ffffffff813963fe>] ? sock_sendmsg+0x6d/0x86
[<ffffffff813959d4>] ? sockfd_lookup_light+0x12/0x5d
[<ffffffff8139650a>] ? SyS_sendto+0xf3/0x11b
[<ffffffff810d5738>] ? new_sync_read+0x82/0xaa
[<ffffffff813ddd19>] compat_ip_setsockopt+0x3b/0x99
[<ffffffff813fb24a>] compat_raw_setsockopt+0x11/0x32
[<ffffffff81399052>] compat_sock_common_setsockopt+0x18/0x1f
[<ffffffff813c4d05>] compat_SyS_setsockopt+0x1a9/0x1cf
[<ffffffff813c4149>] compat_SyS_socketcall+0x180/0x1e3
[<ffffffff81488ea1>] cstar_dispatch+0x7/0x1e

Signed-off-by: Ani Sinha <ani@arista.com>
---
 net/ipv4/ipmr.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index c803458..a1fc97a 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1674,8 +1674,8 @@ static inline int ipmr_forward_finish(struct sk_buff *skb)
 {
 	struct ip_options *opt = &(IPCB(skb)->opt);
 
-	IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTFORWDATAGRAMS);
-	IP_ADD_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTOCTETS, skb->len);
+	IP_INC_STATS(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTFORWDATAGRAMS);
+	IP_ADD_STATS(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTOCTETS, skb->len);
 
 	if (unlikely(opt->optlen))
 		ip_forward_options(skb);
@@ -1737,7 +1737,7 @@ static void ipmr_queue_xmit(struct net *net, struct mr_table *mrt,
 		 * to blackhole.
 		 */
 
-		IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
+		IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
 		ip_rt_put(rt);
 		goto out_free;
 	}
-- 
1.8.1.4

Re: [PATCH -stable 3.18, backport] ipmr: fix possible race resulting from improper usage of IP_INC_STATS_BH() in preemptible context.

[Eric Dumazet]

On Mon, 2015-11-02 at 16:40 -0800, Ani Sinha wrote:
> [ Upstream commit 44f49dd8b5a606870a1f2 ] 

Please carefully read Documentation/networking/netdev-FAQ.txt

A: Normally Greg Kroah-Hartman collects stable commits himself, but
   for networking, Dave collects up patches he deems critical for the
   networking subsystem, and then hands them off to Greg.

   There is a patchworks queue that you can see here:
        http://patchwork.ozlabs.org/bundle/davem/stable/?state=*

   It contains the patches which Dave has selected, but not yet handed
   off to Greg.  If Greg already has the patch, then it will be here:
        http://git.kernel.org/cgit/linux/kernel/git/stable/stable-queue.git

   A quick way to find whether the patch is in this stable-queue is
   to simply clone the repo, and then git grep the mainline commit ID, e.g.

        stable-queue$ git grep -l 284041ef21fdf2e
        releases/3.0.84/ipv6-fix-possible-crashes-in-ip6_cork_release.patch
        releases/3.4.51/ipv6-fix-possible-crashes-in-ip6_cork_release.patch
        releases/3.9.8/ipv6-fix-possible-crashes-in-ip6_cork_release.patch
        stable/stable-queue$

Re: [PATCH -stable 3.18, backport] ipmr: fix possible race resulting from improper usage of IP_INC_STATS_BH() in preemptible context.

[Ani Sinha]

On Mon, Nov 2, 2015 at 4:50 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Mon, 2015-11-02 at 16:40 -0800, Ani Sinha wrote:
>> [ Upstream commit 44f49dd8b5a606870a1f2 ]
>
> Please carefully read Documentation/networking/netdev-FAQ.txt
>
> A: Normally Greg Kroah-Hartman collects stable commits himself, but
>    for networking, Dave collects up patches he deems critical for the
>    networking subsystem, and then hands them off to Greg.
>
>    There is a patchworks queue that you can see here:
>         http://patchwork.ozlabs.org/bundle/davem/stable/?state=*
>
>    It contains the patches which Dave has selected, but not yet handed
>    off to Greg.  If Greg already has the patch, then it will be here:
>         http://git.kernel.org/cgit/linux/kernel/git/stable/stable-queue.git
>
>    A quick way to find whether the patch is in this stable-queue is
>    to simply clone the repo, and then git grep the mainline commit ID, e.g.
>
>         stable-queue$ git grep -l 284041ef21fdf2e
>         releases/3.0.84/ipv6-fix-possible-crashes-in-ip6_cork_release.patch
>         releases/3.4.51/ipv6-fix-possible-crashes-in-ip6_cork_release.patch
>         releases/3.9.8/ipv6-fix-possible-crashes-in-ip6_cork_release.patch
>         stable/stable-queue$

Ah cool! Thanks for the pointer. Seems its already queued up for other
stable kernel version trains  :-)

Re: [PATCH -stable 3.18, backport] ipmr: fix possible race resulting from improper usage of IP_INC_STATS_BH() in preemptible context.

[Ani Sinha]

On Mon, Nov 2, 2015 at 4:50 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Mon, 2015-11-02 at 16:40 -0800, Ani Sinha wrote:
>> [ Upstream commit 44f49dd8b5a606870a1f2 ]
>
> Please carefully read Documentation/networking/netdev-FAQ.txt

I don't see any recent releases of 3.18 version series in Greg KH's
tree. Is the 3.18 stable train being maintained by Sasha here?

http://git.kernel.org/cgit/linux/kernel/git/sashal/linux-stable.git/

If that is the case, should 3.18 specific backport patches be sent
directly to him ?

>
> A: Normally Greg Kroah-Hartman collects stable commits himself, but
>    for networking, Dave collects up patches he deems critical for the
>    networking subsystem, and then hands them off to Greg.
>
>    There is a patchworks queue that you can see here:
>         http://patchwork.ozlabs.org/bundle/davem/stable/?state=*
>
>    It contains the patches which Dave has selected, but not yet handed
>    off to Greg.  If Greg already has the patch, then it will be here:
>         http://git.kernel.org/cgit/linux/kernel/git/stable/stable-queue.git
>
>    A quick way to find whether the patch is in this stable-queue is
>    to simply clone the repo, and then git grep the mainline commit ID, e.g.
>
>         stable-queue$ git grep -l 284041ef21fdf2e
>         releases/3.0.84/ipv6-fix-possible-crashes-in-ip6_cork_release.patch
>         releases/3.4.51/ipv6-fix-possible-crashes-in-ip6_cork_release.patch
>         releases/3.9.8/ipv6-fix-possible-crashes-in-ip6_cork_release.patch
>         stable/stable-queue$
>
>
>

Re: [PATCH -stable 3.18, backport] ipmr: fix possible race resulting from improper usage of IP_INC_STATS_BH() in preemptible context.

[Sasha Levin]

On 11/02/2015 10:32 PM, Ani Sinha wrote:
> On Mon, Nov 2, 2015 at 4:50 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
>> > On Mon, 2015-11-02 at 16:40 -0800, Ani Sinha wrote:
>>> >> [ Upstream commit 44f49dd8b5a606870a1f2 ]
>> >
>> > Please carefully read Documentation/networking/netdev-FAQ.txt
> I don't see any recent releases of 3.18 version series in Greg KH's
> tree. Is the 3.18 stable train being maintained by Sasha here?
> 
> http://git.kernel.org/cgit/linux/kernel/git/sashal/linux-stable.git/
> 
> If that is the case, should 3.18 specific backport patches be sent
> directly to him ?

The documentation is a bit lacking here. I follow the same procedure
as Greg: Dave sends us backports for patches he picks for -stable and
I apply them.

The only difference is that my (currently empty) queue is located elsewhere:
https://git.kernel.org/cgit/linux/kernel/git/sashal/linux-stable.git/log/?h=linux-3.18.y-queue

To sum it up, no need to send anything regarding -stable  net/ to anyone,
Dave does all the heavy lifting there (thanks Dave!).


Thanks,
Sasha