Messages in this thread | | | Subject | Re: [syzbot] WARNING in ex_handler_fprestore | From | "Yu, Yu-cheng" <> | Date | Wed, 26 May 2021 14:21:39 -0700 |
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On 5/26/2021 12:00 AM, Dmitry Vyukov wrote: > On Wed, May 26, 2021 at 2:33 AM Andy Lutomirski <luto@kernel.org> wrote: >> >> On 5/24/21 1:51 AM, syzbot wrote: >>> Hello, >>> >>> syzbot found the following issue on: >>> >>> HEAD commit: 45af60e7 Merge tag 'for-5.13-rc2-tag' of git://git.kernel... >>> git tree: upstream >>> console output: https://syzkaller.appspot.com/x/log.txt?x=1591e9f7d00000 >>> kernel config: https://syzkaller.appspot.com/x/.config?x=18fade5827eb74f7 >>> dashboard link: https://syzkaller.appspot.com/bug?extid=2067e764dbcd10721e2e >>> compiler: Debian clang version 11.0.1-2 >>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11be6bd1d00000 >> >> Hi syz people and x86 people- >> >> I entirely believe that this bug is real and that syzbot bisected it >> correctly, but I'm puzzled by the reproducer. It says: >> >> ptrace$setregs(0xd, r0, 0x0, &(0x7f0000000080)) >> >> I would really, really expect this to result from PTRACE_SETREGSET or >> PTRACE_SETFPREGS, but this is PTRACE_SETREGS. >> >> Am I missing something really obvious here? > > Hi Andy, > > Sometimes syzkaller uses data format from one syscall variant, but > actually invokes another. > But here it does _not_ seem to be the case: 0xd is actually > PTRACE_SETREGS. And the other ptrace calls in the reproducer are > PTRACE_SEIZE and PTRACE_SINGLESTEP. > So I would assume somehow it happened with PTRACE_SETREGS. > Is there any indication from hardware as to what's wrong with fpregs? >
PTRACE_SETREGS can change segment registers. The PTRACE_SETREGS is using some uninitialized memory area. One possibility would be that XRSTORS has a memory operand outside of segment limits.
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