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with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jLcge-0005Bv-D0; Tue, 07 Apr 2020 01:05:56 +0000 Subject: Re: BUG: unable to handle kernel paging request in kernel_get_mempolicy To: Peter Xu , syzbot Cc: akpm@linux-foundation.org, bgeffon@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, torvalds@linux-foundation.org References: <0000000000002b25f105a2a3434d@google.com> <20200407004745.GA48345@xz-x1> From: Randy Dunlap Message-ID: <3ff20c8a-5a26-5e38-42f7-ec751735d47c@infradead.org> Date: Mon, 6 Apr 2020 18:05:54 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200407004745.GA48345@xz-x1> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 4/6/20 5:47 PM, Peter Xu wrote: > On Mon, Apr 06, 2020 at 11:16:13AM -0700, syzbot wrote: >> Hello, >> >> syzbot found the following crash on: >> >> HEAD commit: bef7b2a7 Merge tag 'devicetree-for-5.7' of git://git.kerne.. >> git tree: upstream >> console output: https://syzkaller.appspot.com/x/log.txt?x=13966e8fe00000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=91b674b8f0368e69 >> dashboard link: https://syzkaller.appspot.com/bug?extid=693dc11fcb53120b5559 >> compiler: gcc (GCC) 9.0.0 20181231 (experimental) >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1738b02be00000 >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17d2c76de00000 >> >> The bug was bisected to: >> >> commit 4426e945df588f2878affddf88a51259200f7e29 >> Author: Peter Xu >> Date: Thu Apr 2 04:08:49 2020 +0000 >> >> mm/gup: allow VM_FAULT_RETRY for multiple times >> >> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14ac4a5de00000 >> final crash: https://syzkaller.appspot.com/x/report.txt?x=16ac4a5de00000 >> console output: https://syzkaller.appspot.com/x/log.txt?x=12ac4a5de00000 >> >> IMPORTANT: if you fix the bug, please add the following tag to the commit: >> Reported-by: syzbot+693dc11fcb53120b5559@syzkaller.appspotmail.com >> Fixes: 4426e945df58 ("mm/gup: allow VM_FAULT_RETRY for multiple times") >> >> BUG: unable to handle page fault for address: ffffffff00000000 >> #PF: supervisor read access in kernel mode >> #PF: error_code(0x0000) - not-present page >> PGD 987c067 P4D 987c067 PUD 0 >> Oops: 0000 [#1] PREEMPT SMP KASAN >> CPU: 1 PID: 7181 Comm: syz-executor616 Not tainted 5.6.0-syzkaller #0 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 >> RIP: 0010:page_to_nid include/linux/mm.h:1245 [inline] >> RIP: 0010:lookup_node mm/mempolicy.c:906 [inline] >> RIP: 0010:do_get_mempolicy mm/mempolicy.c:970 [inline] >> RIP: 0010:kernel_get_mempolicy+0x60e/0xfb0 mm/mempolicy.c:1615 >> Code: 88 00 07 00 00 e8 b2 35 c5 ff 4c 8b 7c 24 78 48 b8 00 00 00 00 00 fc ff df 4c 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 fb 08 00 00 <49> 8b 1f 48 c7 c7 ff ff ff ff 48 89 de e8 10 37 c5 ff 48 83 fb ff >> RSP: 0018:ffffc900018d7de8 EFLAGS: 00010246 >> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff81adaaf1 >> RDX: 1fffffffe0000000 RSI: ffffffff81adaafe RDI: 0000000000000005 >> RBP: 0000000000000000 R08: ffff88808de924c0 R09: ffffed1011bd2499 >> R10: ffff88808de924c7 R11: ffffed1011bd2498 R12: 0000000000000000 >> R13: 1ffff9200031afc4 R14: ffffffff89a6df60 R15: ffffffff00000000 >> FS: 00007f848cd4a700(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: ffffffff00000000 CR3: 00000000a7a8d000 CR4: 00000000001406e0 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> Call Trace: >> __do_sys_get_mempolicy mm/mempolicy.c:1633 [inline] >> __se_sys_get_mempolicy mm/mempolicy.c:1629 [inline] >> __x64_sys_get_mempolicy+0xba/0x150 mm/mempolicy.c:1629 >> do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 >> entry_SYSCALL_64_after_hwframe+0x49/0xb3 >> RIP: 0033:0x446719 >> Code: e8 5c b3 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 0b 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00 >> RSP: 002b:00007f848cd49db8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ef >> RAX: ffffffffffffffda RBX: 00000000006dbc28 RCX: 0000000000446719 >> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 >> RBP: 00000000006dbc20 R08: 0000000000000003 R09: 0000000000000000 >> R10: 000000002073b000 R11: 0000000000000246 R12: 00000000006dbc2c >> R13: 00007ffcfe6ba66f R14: 00007f848cd4a9c0 R15: 20c49ba5e353f7cf >> Modules linked in: >> CR2: ffffffff00000000 >> ---[ end trace 0becf554e06291c3 ]--- >> RIP: 0010:page_to_nid include/linux/mm.h:1245 [inline] >> RIP: 0010:lookup_node mm/mempolicy.c:906 [inline] >> RIP: 0010:do_get_mempolicy mm/mempolicy.c:970 [inline] >> RIP: 0010:kernel_get_mempolicy+0x60e/0xfb0 mm/mempolicy.c:1615 >> Code: 88 00 07 00 00 e8 b2 35 c5 ff 4c 8b 7c 24 78 48 b8 00 00 00 00 00 fc ff df 4c 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 fb 08 00 00 <49> 8b 1f 48 c7 c7 ff ff ff ff 48 89 de e8 10 37 c5 ff 48 83 fb ff >> RSP: 0018:ffffc900018d7de8 EFLAGS: 00010246 >> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff81adaaf1 >> RDX: 1fffffffe0000000 RSI: ffffffff81adaafe RDI: 0000000000000005 >> RBP: 0000000000000000 R08: ffff88808de924c0 R09: ffffed1011bd2499 >> R10: ffff88808de924c7 R11: ffffed1011bd2498 R12: 0000000000000000 >> R13: 1ffff9200031afc4 R14: ffffffff89a6df60 R15: ffffffff00000000 >> FS: 00007f848cd4a700(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: ffffffff00000000 CR3: 00000000a7a8d000 CR4: 00000000001406e0 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > Hi, Andrew & all, > > I can reproduce this locally right after I run the test program, and > below patch fixed it for me - the test program can run with quite a > few minutes without crashing again. > > Is there a way I can feed this to the syzbot to re-verify this? Hi Peter, Send the patch. At the top of the email, put something like #syz test It's documented here: https://github.com/google/syzkaller/blob/master/docs/syzbot.md > Thanks, > > 8<--------------------------------------------------------------- > From 23800bff6fa346a4e9b3806dc0cfeb74498df757 Mon Sep 17 00:00:00 2001 > From: Peter Xu > Date: Mon, 6 Apr 2020 20:40:13 -0400 > Subject: [PATCH] mm/mempolicy: Allow lookup_node() to handle fatal signal > > lookup_node() uses gup to pin the page and get node information. It > checks against ret>=0 assuming the page will be filled in. However > it's also possible that gup will return zero, for example, when the > thread is quickly killed with a fatal signal. Teach lookup_node() to > gracefully return an error -EFAULT if it happens. > > Reported-by: syzbot+693dc11fcb53120b5559@syzkaller.appspotmail.com > Fixes: 4426e945df58 ("mm/gup: allow VM_FAULT_RETRY for multiple times") > Signed-off-by: Peter Xu > --- > mm/mempolicy.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 5fb427aed612..1398578db025 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -902,7 +902,10 @@ static int lookup_node(struct mm_struct *mm, unsigned long addr) > > int locked = 1; > err = get_user_pages_locked(addr & PAGE_MASK, 1, 0, &p, &locked); > - if (err >= 0) { > + if (err == 0) { > + /* E.g. GUP interupted by fatal signal */ > + err = -EFAULT; > + } else if (err > 0) { > err = page_to_nid(p); > put_page(p); > } > -- ~Randy Reported-by: Randy Dunlap