netdev - Re: [PATCH net] ppp_async: limit MRU to 64K

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Date: Mon, 05 Feb 2024 13:59:40 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Eric Dumazet <edumazet@...gle.com>, 
 "David S . Miller" <davem@...emloft.net>, 
 Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, 
 eric.dumazet@...il.com, 
 Eric Dumazet <edumazet@...gle.com>, 
 syzbot+c5da1f087c9e4ec6c933@...kaller.appspotmail.com, 
 Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net] ppp_async: limit MRU to 64K

Eric Dumazet wrote:
> syzbot triggered a warning [1] in __alloc_pages():
> 
> WARN_ON_ONCE_GFP(order > MAX_PAGE_ORDER, gfp)
> 
> Willem fixed a similar issue in commit c0a2a1b0d631 ("ppp: limit MRU to 64K")
> 
> Adopt the same sanity check for ppp_async_ioctl(PPPIOCSMRU)
> 
> [1]:
> 
>  WARNING: CPU: 1 PID: 11 at mm/page_alloc.c:4543 __alloc_pages+0x308/0x698 mm/page_alloc.c:4543
> Modules linked in:
> CPU: 1 PID: 11 Comm: kworker/u4:0 Not tainted 6.8.0-rc2-syzkaller-g41bccc98fb79 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
> Workqueue: events_unbound flush_to_ldisc
> pstate: 204000c5 (nzCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>  pc : __alloc_pages+0x308/0x698 mm/page_alloc.c:4543
>  lr : __alloc_pages+0xc8/0x698 mm/page_alloc.c:4537
> sp : ffff800093967580
> x29: ffff800093967660 x28: ffff8000939675a0 x27: dfff800000000000
> x26: ffff70001272ceb4 x25: 0000000000000000 x24: ffff8000939675c0
> x23: 0000000000000000 x22: 0000000000060820 x21: 1ffff0001272ceb8
> x20: ffff8000939675e0 x19: 0000000000000010 x18: ffff800093967120
> x17: ffff800083bded5c x16: ffff80008ac97500 x15: 0000000000000005
> x14: 1ffff0001272cebc x13: 0000000000000000 x12: 0000000000000000
> x11: ffff70001272cec1 x10: 1ffff0001272cec0 x9 : 0000000000000001
> x8 : ffff800091c91000 x7 : 0000000000000000 x6 : 000000000000003f
> x5 : 00000000ffffffff x4 : 0000000000000000 x3 : 0000000000000020
> x2 : 0000000000000008 x1 : 0000000000000000 x0 : ffff8000939675e0
> Call trace:
>   __alloc_pages+0x308/0x698 mm/page_alloc.c:4543
>   __alloc_pages_node include/linux/gfp.h:238 [inline]
>   alloc_pages_node include/linux/gfp.h:261 [inline]
>   __kmalloc_large_node+0xbc/0x1fc mm/slub.c:3926
>   __do_kmalloc_node mm/slub.c:3969 [inline]
>   __kmalloc_node_track_caller+0x418/0x620 mm/slub.c:4001
>   kmalloc_reserve+0x17c/0x23c net/core/skbuff.c:590
>   __alloc_skb+0x1c8/0x3d8 net/core/skbuff.c:651
>   __netdev_alloc_skb+0xb8/0x3e8 net/core/skbuff.c:715
>   netdev_alloc_skb include/linux/skbuff.h:3235 [inline]
>   dev_alloc_skb include/linux/skbuff.h:3248 [inline]
>   ppp_async_input drivers/net/ppp/ppp_async.c:863 [inline]
>   ppp_asynctty_receive+0x588/0x186c drivers/net/ppp/ppp_async.c:341
>   tty_ldisc_receive_buf+0x12c/0x15c drivers/tty/tty_buffer.c:390
>   tty_port_default_receive_buf+0x74/0xac drivers/tty/tty_port.c:37
>   receive_buf drivers/tty/tty_buffer.c:444 [inline]
>   flush_to_ldisc+0x284/0x6e4 drivers/tty/tty_buffer.c:494
>   process_one_work+0x694/0x1204 kernel/workqueue.c:2633
>   process_scheduled_works kernel/workqueue.c:2706 [inline]
>   worker_thread+0x938/0xef4 kernel/workqueue.c:2787
>   kthread+0x288/0x310 kernel/kthread.c:388
>   ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Reported-and-tested-by: syzbot+c5da1f087c9e4ec6c933@...kaller.appspotmail.com
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Willem de Bruijn <willemb@...gle.com>

Reviewed-by: Willem de Bruijn <willemb@...gle.com>