From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by kanga.kvack.org (Postfix) with ESMTP id 6FD6F8E0002 for ; Sun, 13 Jan 2019 22:59:12 -0500 (EST) Received: by mail-wm1-f69.google.com with SMTP id e1so1372354wmg.0 for ; Sun, 13 Jan 2019 19:59:12 -0800 (PST) Received: from mail-40130.protonmail.ch (mail-40130.protonmail.ch. [185.70.40.130]) by mx.google.com with ESMTPS id v84si18636518wma.79.2019.01.13.19.59.10 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 13 Jan 2019 19:59:10 -0800 (PST) Date: Mon, 14 Jan 2019 03:59:04 +0000 From: Esme Reply-To: Esme Subject: Re: [PATCH v2] rbtree: fix the red root Message-ID: In-Reply-To: References: <20190111181600.GJ6310@bombadil.infradead.org> <20190111205843.25761-1-cai@lca.pw> <864d6b85-3336-4040-7c95-7d9615873777@lechnology.com> <8v11ZOLyufY7NLAHDFApGwXOO_wGjVHtsbw1eiZ__YvI9EZCDe_4FNmlp0E-39lnzGQHhHAczQ6Q6lQPzVU2V6krtkblM8IFwIXPHZCuqGE=@protonmail.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: "dgilbert@interlog.com" Cc: Qian Cai , David Lechner , Michel Lespinasse , Andrew Morton , "jejb@linux.ibm.com" , "martin.petersen@oracle.com" , "joeypabalinas@gmail.com" , linux-mm , LKML =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90 Original Me= ssage =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90 On Sunday, January 13, 2019 10:52 PM, Douglas Gilbert wrote: > On 2019-01-13 10:07 p.m., Esme wrote: > > > =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90 Origina= l Message =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80= =90 > > On Sunday, January 13, 2019 9:33 PM, Qian Cai cai@lca.pw wrote: > > > > > On 1/13/19 9:20 PM, David Lechner wrote: > > > > > > > On 1/11/19 8:58 PM, Michel Lespinasse wrote: > > > > > > > > > On Fri, Jan 11, 2019 at 3:47 PM David Lechner david@lechnology.co= m wrote: > > > > > > > > > > > On 1/11/19 2:58 PM, Qian Cai wrote: > > > > > > > > > > > > > A GPF was reported, > > > > > > > kasan: CONFIG_KASAN_INLINE enabled > > > > > > > kasan: GPF could be caused by NULL-ptr deref or user memory a= ccess > > > > > > > general protection fault: 0000 [#1] SMP KASAN > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 kasan_= die_handler.cold.22+0x11/0x31 > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 notifi= er_call_chain+0x17b/0x390 > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 atomic= _notifier_call_chain+0xa7/0x1b0 > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 notify= _die+0x1be/0x2e0 > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 do_gen= eral_protection+0x13e/0x330 > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 genera= l_protection+0x1e/0x30 > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 rb_ins= ert_color+0x189/0x1480 > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 create= _object+0x785/0xca0 > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 kmemle= ak_alloc+0x2f/0x50 > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 kmem_c= ache_alloc+0x1b9/0x3c0 > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 getnam= e_flags+0xdb/0x5d0 > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 getnam= e+0x1e/0x20 > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 do_sys= _open+0x3a1/0x7d0 > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 __x64_= sys_open+0x7e/0xc0 > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 do_sys= call_64+0x1b3/0x820 > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 entry_= SYSCALL_64_after_hwframe+0x49/0xbe > > > > > > > It turned out, > > > > > > > gparent =3D rb_red_parent(parent); > > > > > > > tmp =3D gparent->rb_right; <-- GPF was triggered here. > > > > > > > Apparently, "gparent" is NULL which indicates "parent" is rbt= ree's root > > > > > > > which is red. Otherwise, it will be treated properly a few li= nes above. > > > > > > > /* > > > > > > > =C2=A0=C2=A0 * If there is a black parent, we are done. > > > > > > > =C2=A0=C2=A0 * Otherwise, take some corrective action as, > > > > > > > =C2=A0=C2=A0 * per 4), we don't want a red root or two > > > > > > > =C2=A0=C2=A0 * consecutive red nodes. > > > > > > > =C2=A0=C2=A0 */ > > > > > > > if(rb_is_black(parent)) > > > > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 break; > > > > > > > Hence, it violates the rule #1 (the root can't be red) and ne= ed a fix > > > > > > > up, and also add a regression test for it. This looks like wa= s > > > > > > > introduced by 6d58452dc06 where it no longer always paint the= root as > > > > > > > black. > > > > > > > Fixes: 6d58452dc06 (rbtree: adjust root color in rb_insert_co= lor() only > > > > > > > when necessary) > > > > > > > Reported-by: Esme esploit@protonmail.ch > > > > > > > Tested-by: Joey Pabalinas joeypabalinas@gmail.com > > > > > > > Signed-off-by: Qian Cai cai@lca.pw > > > > > > > > > > > > Tested-by: David Lechner david@lechnology.com > > > > > > FWIW, this fixed the following crash for me: > > > > > > Unable to handle kernel NULL pointer dereference at virtual add= ress 00000004 > > > > > > > > > > Just to clarify, do you have a way to reproduce this crash withou= t the fix ? > > > > > > > > I am starting to suspect that my crash was caused by some new code > > > > in the drm-misc-next tree that might be causing a memory corruption= . > > > > It threw me off that the stack trace didn't contain anything relate= d > > > > to drm. > > > > See: https://patchwork.freedesktop.org/patch/276719/ > > > > > > It may be useful for those who could reproduce this issue to turn on = those > > > memory corruption debug options to narrow down a bit. > > > CONFIG_DEBUG_PAGEALLOC=3Dy > > > CONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT=3Dy > > > CONFIG_KASAN=3Dy > > > CONFIG_KASAN_GENERIC=3Dy > > > CONFIG_SLUB_DEBUG_ON=3Dy > > > > I have been on SLAB, I configured SLAB DEBUG with a fresh pull from git= hub. Linux syzkaller 5.0.0-rc2 #9 SMP Sun Jan 13 21:57:40 EST 2019 x86_64 > > ... > > In an effort to get a different stack into the kernel, I felt that noth= ing works better than fork bomb? :) > > Let me know if that helps. > > root@syzkaller:~# gcc -o test3 test3.c > > root@syzkaller:~# while : ; do ./test3 & done > > And is test3 the same multi-threaded program that enters the kernel via > /dev/sg0 and then calls SCSI_IOCTL_SEND_COMMAND which goes to the SCSI > mid-level and thence to the block layer? > > And please remind me, does it also fail on lk 4.20.2 ? > > Doug Gilbert Yes, the same C repro from the earlier thread. It was a 4.20.0 kernel wher= e it was first detected. I can move to 4.20.2 and see if that changes anyt= hing. Esme