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Date: Tue, 5 May 2020 00:02:15 -0700 From: Cong Wang <xiyou.wangcong@...il.com> To: Josh Poimboeuf <jpoimboe@...hat.com> Cc: syzbot <syzbot+e73ceacfd8560cc8a3ca@...kaller.appspotmail.com>, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...hat.com>, Linux Kernel Network Developers <netdev@...r.kernel.org>, Peter Zijlstra <peterz@...radead.org>, shile.zhang@...ux.alibaba.com, syzkaller-bugs <syzkaller-bugs@...glegroups.com>, Thomas Gleixner <tglx@...utronix.de>, x86 <x86@...nel.org> Subject: Re: BUG: stack guard page was hit in unwind_next_frame On Mon, May 4, 2020 at 6:06 PM Cong Wang <xiyou.wangcong@...il.com> wrote: > > On Mon, May 4, 2020 at 12:08 PM Josh Poimboeuf <jpoimboe@...hat.com> wrote: > > > > On Sat, May 02, 2020 at 11:36:11PM -0700, syzbot wrote: > > > Hello, > > > > > > syzbot found the following crash on: > > > > > > HEAD commit: 8999dc89 net/x25: Fix null-ptr-deref in x25_disconnect > > > git tree: net > > > console output: https://syzkaller.appspot.com/x/log.txt?x=16004440100000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=b7a70e992f2f9b68 > > > dashboard link: https://syzkaller.appspot.com/bug?extid=e73ceacfd8560cc8a3ca > > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > > > > > Unfortunately, I don't have any reproducer for this crash yet. > > > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > > Reported-by: syzbot+e73ceacfd8560cc8a3ca@...kaller.appspotmail.com > > > > Infinite loop in network code. > > It is not a loop, it is an unbound recursion where netdev events > trigger between bond master and slave back and forth. > > Let me see how this can be fixed properly. The following patch works for me, I think it is reasonable to stop the netdev event propagation from upper to lower device, but I am not sure whether this will miss the netdev event in complex multi-layer setups. diff --git a/net/core/dev.c b/net/core/dev.c index 522288177bbd..ece50ae346c3 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -8907,7 +8907,7 @@ static void netdev_sync_lower_features(struct net_device *upper, netdev_dbg(upper, "Disabling feature %pNF on lower dev %s.\n", &feature, lower->name); lower->wanted_features &= ~feature; - netdev_update_features(lower); + __netdev_update_features(lower); if (unlikely(lower->features & feature)) netdev_WARN(upper, "failed to disable %pNF on %s!\n",
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