Messages in this thread | | | From | Dmitry Vyukov <> | Date | Fri, 6 Apr 2018 17:40:01 +0200 | Subject | Re: KASAN: alloca-out-of-bounds Read in unwind_next_frame |
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On Fri, Apr 6, 2018 at 5:36 PM, Josh Poimboeuf <jpoimboe@redhat.com> wrote: > On Thu, Apr 05, 2018 at 05:02:02PM -0700, syzbot wrote: >> Hello, >> >> syzbot hit the following crash on upstream commit >> 06dd3dfeea60e2a6457a6aedf97afc8e6d2ba497 (Thu Apr 5 03:07:20 2018 +0000) >> Merge tag 'char-misc-4.17-rc1' of >> git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc >> syzbot dashboard link: >> https://syzkaller.appspot.com/bug?extid=9d1d9866b0b8ee6e0a8c >> >> syzkaller reproducer: >> https://syzkaller.appspot.com/x/repro.syz?id=6478299081474048 >> Raw console output: >> https://syzkaller.appspot.com/x/log.txt?id=5324218015154176 >> Kernel config: https://syzkaller.appspot.com/x/.config?id=216543573824217049 >> compiler: gcc (GCC) 8.0.1 20180301 (experimental) >> >> IMPORTANT: if you fix the bug, please add the following tag to the commit: >> Reported-by: syzbot+9d1d9866b0b8ee6e0a8c@syzkaller.appspotmail.com >> It will help syzbot understand when the bug is fixed. See footer for >> details. >> If you forward the report, please keep this part and the footer. >> >> ================================================================== >> BUG: KASAN: alloca-out-of-bounds in __read_once_size >> include/linux/compiler.h:188 [inline] >> BUG: KASAN: alloca-out-of-bounds in unwind_next_frame.part.7+0x7ce/0x9c0 >> arch/x86/kernel/unwind_frame.c:326 >> Read of size 8 at addr ffff8801b05e67f8 by task syz-executor2/11326 > > This looks like a KASAN bug. > > The FP unwinder was unwinding from an interrupt which hit while running > in kasan_unpoison_shadow(): > >> RIP: 0010:kasan_unpoison_shadow+0x1/0x50 mm/kasan/kasan.c:68 >> RSP: 0018:ffff8801b05e67e8 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff13 >> RAX: ffff8801c1b24100 RBX: 0000000000000000 RCX: ffffffff859d4219 >> RDX: 0000000000000000 RSI: 00000000000000a8 RDI: ffff8801b05e6760 >> RBP: ffff8801b05e67f8 R08: ffff8801c1b24100 R09: ffffed003b6046c2 >> R10: ffffed003b6046c2 R11: ffff8801db023613 R12: 0000000000000015 >> R13: 0000000000000001 R14: 0000000000000016 R15: dffffc0000000000 > > So at first glance it seemed like a race condition. However, the > unwinder was only trying to dereference the frame pointer (RBP: > ffff8801b05e67f8), which should have never been poisoned in the first > place. > > So it looks like a bug in the KASAN alloca poisoning.
Hi Josh,
You seen my previous message, right? Or was it lost somehow?
https://groups.google.com/d/msg/syzkaller-bugs/IcKqxHzhmQc/KAL6o7tOCAAJ
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