netdev - Re: [PATCH net] bridge: check for null fdb->dst before notifying switchdev drivers

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Message-ID: <90a37c67-6284-fccc-2477-da654f53c3a1@mellanox.com>
Date:   Sun, 27 Aug 2017 11:46:43 +0300
From:   Arkadi Sharshevsky <arkadis@...lanox.com>
To:     Roopa Prabhu <roopa@...ulusnetworks.com>, davem@...emloft.net
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net] bridge: check for null fdb->dst before notifying
 switchdev drivers



On 08/27/2017 07:13 AM, Roopa Prabhu wrote:
> From: Roopa Prabhu <roopa@...ulusnetworks.com>
> 
> current switchdev drivers dont seem to support offloading fdb
> entries pointing to the bridge device which have fdb->dst
> not set to any port. This patch adds a NULL fdb->dst check in
> the switchdev notifier code.
> 
> This patch fixes the below NULL ptr dereference:
> $bridge fdb add 00:02:00:00:00:33 dev br0 self
> 
> [   69.953374] BUG: unable to handle kernel NULL pointer dereference at
> 0000000000000008
> [   69.954044] IP: br_switchdev_fdb_notify+0x29/0x80
> [   69.954044] PGD 66527067
> [   69.954044] P4D 66527067
> [   69.954044] PUD 7899c067
> [   69.954044] PMD 0
> [   69.954044]
> [   69.954044] Oops: 0000 [#1] SMP
> [   69.954044] Modules linked in:
> [   69.954044] CPU: 1 PID: 3074 Comm: bridge Not tainted 4.13.0-rc6+ #1
> [   69.954044] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS rel-1.7.5.1-0-g8936dbb-20141113_115728-nilsson.home.kraxel.org
> 04/01/2014
> [   69.954044] task: ffff88007b827140 task.stack: ffffc90001564000
> [   69.954044] RIP: 0010:br_switchdev_fdb_notify+0x29/0x80
> [   69.954044] RSP: 0018:ffffc90001567918 EFLAGS: 00010246
> [   69.954044] RAX: 0000000000000000 RBX: ffff8800795e0880 RCX:
> 00000000000000c0
> [   69.954044] RDX: ffffc90001567920 RSI: 000000000000001c RDI:
> ffff8800795d0600
> [   69.954044] RBP: ffffc90001567938 R08: ffff8800795d0600 R09:
> 0000000000000000
> [   69.954044] R10: ffffc90001567a88 R11: ffff88007b849400 R12:
> ffff8800795e0880
> [   69.954044] R13: ffff8800795d0600 R14: ffffffff81ef8880 R15:
> 000000000000001c
> [   69.954044] FS:  00007f93d3085700(0000) GS:ffff88007fd00000(0000)
> knlGS:0000000000000000
> [   69.954044] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   69.954044] CR2: 0000000000000008 CR3: 0000000066551000 CR4:
> 00000000000006e0
> [   69.954044] Call Trace:
> [   69.954044]  fdb_notify+0x3f/0xf0
> [   69.954044]  __br_fdb_add.isra.12+0x1a7/0x370
> [   69.954044]  br_fdb_add+0x178/0x280
> [   69.954044]  rtnl_fdb_add+0x10a/0x200
> [   69.954044]  rtnetlink_rcv_msg+0x1b4/0x240
> [   69.954044]  ? skb_free_head+0x21/0x40
> [   69.954044]  ? rtnl_calcit.isra.18+0xf0/0xf0
> [   69.954044]  netlink_rcv_skb+0xed/0x120
> [   69.954044]  rtnetlink_rcv+0x15/0x20
> [   69.954044]  netlink_unicast+0x180/0x200
> [   69.954044]  netlink_sendmsg+0x291/0x370
> [   69.954044]  ___sys_sendmsg+0x180/0x2e0
> [   69.954044]  ? filemap_map_pages+0x2db/0x370
> [   69.954044]  ? do_wp_page+0x11d/0x420
> [   69.954044]  ? __handle_mm_fault+0x794/0xd80
> [   69.954044]  ? vma_link+0xcb/0xd0
> [   69.954044]  __sys_sendmsg+0x4c/0x90
> [   69.954044]  SyS_sendmsg+0x12/0x20
> [   69.954044]  do_syscall_64+0x63/0xe0
> [   69.954044]  entry_SYSCALL64_slow_path+0x25/0x25
> [   69.954044] RIP: 0033:0x7f93d2bad690
> [   69.954044] RSP: 002b:00007ffc7217a638 EFLAGS: 00000246 ORIG_RAX:
> 000000000000002e
> [   69.954044] RAX: ffffffffffffffda RBX: 00007ffc72182eac RCX:
> 00007f93d2bad690
> [   69.954044] RDX: 0000000000000000 RSI: 00007ffc7217a670 RDI:
> 0000000000000003
> [   69.954044] RBP: 0000000059a1f7f8 R08: 0000000000000006 R09:
> 000000000000000a
> [   69.954044] R10: 00007ffc7217a400 R11: 0000000000000246 R12:
> 00007ffc7217a670
> [   69.954044] R13: 00007ffc72182a98 R14: 00000000006114c0 R15:
> 00007ffc72182aa0
> [   69.954044] Code: 1f 00 66 66 66 66 90 55 48 89 e5 48 83 ec 20 f6 47
> 20 04 74 0a 83 fe 1c 74 09 83 fe 1d 74 2c c9 66 90 c3 48 8b 47 10 48 8d
> 55 e8 <48> 8b 70 08 0f b7 47 1e 48 83 c7 18 48 89 7d f0 bf 03 00 00 00
> [   69.954044] RIP: br_switchdev_fdb_notify+0x29/0x80 RSP:
> ffffc90001567918
> [   69.954044] CR2: 0000000000000008
> [   69.954044] ---[ end trace 03e9eec4a82c238b ]---
> 
> Fixes: 6b26b51b1d13 ("net: bridge: Add support for notifying devices about FDB add/del")
> Signed-off-by: Roopa Prabhu <roopa@...ulusnetworks.com>
> ---
>  net/bridge/br_switchdev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/bridge/br_switchdev.c b/net/bridge/br_switchdev.c
> index 181a44d..f6b1c7d 100644
> --- a/net/bridge/br_switchdev.c
> +++ b/net/bridge/br_switchdev.c
> @@ -115,7 +115,7 @@ br_switchdev_fdb_call_notifiers(bool adding, const unsigned char *mac,
>  void
>  br_switchdev_fdb_notify(const struct net_bridge_fdb_entry *fdb, int type)
>  {
> -	if (!fdb->added_by_user)
> +	if (!fdb->added_by_user || !fdb->dst)
>  		return;
>  
>  	switch (type) {
> 

Thanks, missed that.
Arkadi