Messages in this thread | | | Subject | Re: [PATCH v2] rbtree: fix the red root | From | Douglas Gilbert <> | Date | Sun, 13 Jan 2019 22:52:16 -0500 |
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On 2019-01-13 10:07 p.m., Esme wrote: > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ > 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.com 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 access >>>>>> general protection fault: 0000 [#1] SMP KASAN >>>>>> kasan_die_handler.cold.22+0x11/0x31 >>>>>> notifier_call_chain+0x17b/0x390 >>>>>> atomic_notifier_call_chain+0xa7/0x1b0 >>>>>> notify_die+0x1be/0x2e0 >>>>>> do_general_protection+0x13e/0x330 >>>>>> general_protection+0x1e/0x30 >>>>>> rb_insert_color+0x189/0x1480 >>>>>> create_object+0x785/0xca0 >>>>>> kmemleak_alloc+0x2f/0x50 >>>>>> kmem_cache_alloc+0x1b9/0x3c0 >>>>>> getname_flags+0xdb/0x5d0 >>>>>> getname+0x1e/0x20 >>>>>> do_sys_open+0x3a1/0x7d0 >>>>>> __x64_sys_open+0x7e/0xc0 >>>>>> do_syscall_64+0x1b3/0x820 >>>>>> entry_SYSCALL_64_after_hwframe+0x49/0xbe >>>>>> It turned out, >>>>>> gparent = rb_red_parent(parent); >>>>>> tmp = gparent->rb_right; <-- GPF was triggered here. >>>>>> Apparently, "gparent" is NULL which indicates "parent" is rbtree's root >>>>>> which is red. Otherwise, it will be treated properly a few lines above. >>>>>> /* >>>>>> * If there is a black parent, we are done. >>>>>> * Otherwise, take some corrective action as, >>>>>> * per 4), we don't want a red root or two >>>>>> * consecutive red nodes. >>>>>> */ >>>>>> if(rb_is_black(parent)) >>>>>> break; >>>>>> Hence, it violates the rule #1 (the root can't be red) and need a fix >>>>>> up, and also add a regression test for it. This looks like was >>>>>> introduced by 6d58452dc06 where it no longer always paint the root as >>>>>> black. >>>>>> >>>>>> Fixes: 6d58452dc06 (rbtree: adjust root color in rb_insert_color() 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 address 00000004 >>>> >>>> Just to clarify, do you have a way to reproduce this crash without 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 related >>> 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=y >> CONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT=y >> CONFIG_KASAN=y >> CONFIG_KASAN_GENERIC=y >> CONFIG_SLUB_DEBUG_ON=y > > I have been on SLAB, I configured SLAB DEBUG with a fresh pull from github. 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 nothing 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
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