diff mbox series

[net-next] ip6_tunnel: sit: proper dev_{hold|put} in ndo_[un]init methods

Message ID 20210330064551.545964-1-eric.dumazet@gmail.com (mailing list archive)
State Accepted
Commit 48bb5697269a7cbe5194dbb044dc38c517e34c58
Delegated to: Netdev Maintainers
Headers show
Series [net-next] ip6_tunnel: sit: proper dev_{hold|put} in ndo_[un]init methods | expand

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Context Check Description
netdev/cover_letter success Link
netdev/fixes_present success Link
netdev/patch_count success Link
netdev/tree_selection success Clearly marked for net-next
netdev/subject_prefix success Link
netdev/cc_maintainers warning 2 maintainers not CCed: yoshfuji@linux-ipv6.org dsahern@kernel.org
netdev/source_inline success Was 0 now: 0
netdev/verify_signedoff success Link
netdev/module_param success Was 0 now: 0
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/verify_fixes success Link
netdev/checkpatch warning WARNING: Possible repeated word: 'Google'
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/header_inline success Link

Commit Message

Eric Dumazet March 30, 2021, 6:45 a.m. UTC 
From: Eric Dumazet <edumazet@google.com>

Same reasons than for the previous commits :
6289a98f0817 ("sit: proper dev_{hold|put} in ndo_[un]init methods")
40cb881b5aaa ("ip6_vti: proper dev_{hold|put} in ndo_[un]init methods")
7f700334be9a ("ip6_gre: proper dev_{hold|put} in ndo_[un]init methods")

After adopting CONFIG_PCPU_DEV_REFCNT=n option, syzbot was able to trigger
a warning [1]

Issue here is that:

- all dev_put() should be paired with a corresponding prior dev_hold().

- A driver doing a dev_put() in its ndo_uninit() MUST also
  do a dev_hold() in its ndo_init(), only when ndo_init()
  is returning 0.

Otherwise, register_netdevice() would call ndo_uninit()
in its error path and release a refcount too soon.

[1]
WARNING: CPU: 1 PID: 21059 at lib/refcount.c:31 refcount_warn_saturate+0xbf/0x1e0 lib/refcount.c:31
Modules linked in:
CPU: 1 PID: 21059 Comm: syz-executor.4 Not tainted 5.12.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:refcount_warn_saturate+0xbf/0x1e0 lib/refcount.c:31
Code: 1d 6a 5a e8 09 31 ff 89 de e8 8d 1a ab fd 84 db 75 e0 e8 d4 13 ab fd 48 c7 c7 a0 e1 c1 89 c6 05 4a 5a e8 09 01 e8 2e 36 fb 04 <0f> 0b eb c4 e8 b8 13 ab fd 0f b6 1d 39 5a e8 09 31 ff 89 de e8 58
RSP: 0018:ffffc900025aefe8 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000040000 RSI: ffffffff815c51f5 RDI: fffff520004b5def
RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff815bdf8e R11: 0000000000000000 R12: ffff888023488568
R13: ffff8880254e9000 R14: 00000000dfd82cfd R15: ffff88802ee2d7c0
FS:  00007f13bc590700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0943e74000 CR3: 0000000025273000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 __refcount_dec include/linux/refcount.h:344 [inline]
 refcount_dec include/linux/refcount.h:359 [inline]
 dev_put include/linux/netdevice.h:4135 [inline]
 ip6_tnl_dev_uninit+0x370/0x3d0 net/ipv6/ip6_tunnel.c:387
 register_netdevice+0xadf/0x1500 net/core/dev.c:10308
 ip6_tnl_create2+0x1b5/0x400 net/ipv6/ip6_tunnel.c:263
 ip6_tnl_newlink+0x312/0x580 net/ipv6/ip6_tunnel.c:2052
 __rtnl_newlink+0x1062/0x1710 net/core/rtnetlink.c:3443
 rtnl_newlink+0x64/0xa0 net/core/rtnetlink.c:3491
 rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5553
 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2502
 netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1338
 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1927
 sock_sendmsg_nosec net/socket.c:654 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:674
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2350
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2404
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2433
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Fixes: 919067cc845f ("net: add CONFIG_PCPU_DEV_REFCNT")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
---
 net/ipv6/ip6_tunnel.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Eric Dumazet March 31, 2021, 6 a.m. UTC | #1 
On Tue, Mar 30, 2021 at 8:45 AM Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
> From: Eric Dumazet <edumazet@google.com>
>
> Same reasons than for the previous commits :
> 6289a98f0817 ("sit: proper dev_{hold|put} in ndo_[un]init methods")
> 40cb881b5aaa ("ip6_vti: proper dev_{hold|put} in ndo_[un]init methods")
> 7f700334be9a ("ip6_gre: proper dev_{hold|put} in ndo_[un]init methods")
>
> After adopting CONFIG_PCPU_DEV_REFCNT=n option, syzbot was able to trigger
> a warning [1]
>
> Issue here is that:
>
> - all dev_put() should be paired with a corresponding prior dev_hold().
>
> - A driver doing a dev_put() in its ndo_uninit() MUST also
>   do a dev_hold() in its ndo_init(), only when ndo_init()
>   is returning 0.
>
> Otherwise, register_netdevice() would call ndo_uninit()
> in its error path and release a refcount too soon.
>
>

Note to David & Jakub

Can you merge this patch so that I can send my global fix for fallback
tunnels, with a correct Fixes: tag for this patch ?

Thanks !
Eric Dumazet March 31, 2021, 6:01 a.m. UTC | #2 
On Wed, Mar 31, 2021 at 8:00 AM Eric Dumazet <edumazet@google.com> wrote:
>
> On Tue, Mar 30, 2021 at 8:45 AM Eric Dumazet <eric.dumazet@gmail.com> wrote:
> >
> > From: Eric Dumazet <edumazet@google.com>
> >
> > Same reasons than for the previous commits :
> > 6289a98f0817 ("sit: proper dev_{hold|put} in ndo_[un]init methods")
> > 40cb881b5aaa ("ip6_vti: proper dev_{hold|put} in ndo_[un]init methods")
> > 7f700334be9a ("ip6_gre: proper dev_{hold|put} in ndo_[un]init methods")
> >
> > After adopting CONFIG_PCPU_DEV_REFCNT=n option, syzbot was able to trigger
> > a warning [1]
> >
> > Issue here is that:
> >
> > - all dev_put() should be paired with a corresponding prior dev_hold().
> >
> > - A driver doing a dev_put() in its ndo_uninit() MUST also
> >   do a dev_hold() in its ndo_init(), only when ndo_init()
> >   is returning 0.
> >
> > Otherwise, register_netdevice() would call ndo_uninit()
> > in its error path and release a refcount too soon.
> >
> >
>
> Note to David & Jakub
>
> Can you merge this patch so that I can send my global fix for fallback
> tunnels, with a correct Fixes: tag for this patch ?
>
> Thanks !

Forgot to attach what the global fix would look like :
patchwork-bot+netdevbpf@kernel.org March 31, 2021, 9:30 p.m. UTC | #3 
Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Mon, 29 Mar 2021 23:45:51 -0700 you wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> Same reasons than for the previous commits :
> 6289a98f0817 ("sit: proper dev_{hold|put} in ndo_[un]init methods")
> 40cb881b5aaa ("ip6_vti: proper dev_{hold|put} in ndo_[un]init methods")
> 7f700334be9a ("ip6_gre: proper dev_{hold|put} in ndo_[un]init methods")
> 
> [...]

Here is the summary with links:
  - [net-next] ip6_tunnel: sit: proper dev_{hold|put} in ndo_[un]init methods
    https://git.kernel.org/netdev/net-next/c/48bb5697269a

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
David Miller March 31, 2021, 9:38 p.m. UTC | #4 
From: Eric Dumazet <edumazet@google.com>
Date: Wed, 31 Mar 2021 08:00:24 +0200

> Can you merge this patch so that I can send my global fix for fallback
> tunnels, with a correct Fixes: tag for this patch ?

Done.
Eric Dumazet March 31, 2021, 9:40 p.m. UTC | #5 
On Wed, Mar 31, 2021 at 11:39 PM David Miller <davem@davemloft.net> wrote:
>
> From: Eric Dumazet <edumazet@google.com>
> Date: Wed, 31 Mar 2021 08:00:24 +0200
>
> > Can you merge this patch so that I can send my global fix for fallback
> > tunnels, with a correct Fixes: tag for this patch ?
>
> Done.

Thanks a lot David, I have sent the followup patch, with updated Fixes: tags.
diff mbox series

Patch

diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index cd78f5b2cd75e20a79fd6c4cbfafd548204c2b7c..67ee9d58ec5efcc81e8b27406bd4f57a0caea70b 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -266,7 +266,6 @@  static int ip6_tnl_create2(struct net_device *dev)
 
 	strcpy(t->parms.name, dev->name);
 
-	dev_hold(dev);
 	ip6_tnl_link(ip6n, t);
 	return 0;
 
@@ -1882,6 +1881,7 @@  ip6_tnl_dev_init_gen(struct net_device *dev)
 	dev->min_mtu = ETH_MIN_MTU;
 	dev->max_mtu = IP6_MAX_MTU - dev->hard_header_len;
 
+	dev_hold(dev);
 	return 0;
 
 destroy_dst: