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Diffstat (limited to 'results/classifier/118/assembly-x86/1824344')
| -rw-r--r-- | results/classifier/118/assembly-x86/1824344 | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/results/classifier/118/assembly-x86/1824344 b/results/classifier/118/assembly-x86/1824344 new file mode 100644 index 000000000..0de0a16c4 --- /dev/null +++ b/results/classifier/118/assembly-x86/1824344 @@ -0,0 +1,118 @@ +x86: 0.950 +i386: 0.943 +kernel: 0.896 +assembly: 0.842 +architecture: 0.838 +ppc: 0.779 +register: 0.635 +device: 0.543 +semantic: 0.396 +PID: 0.373 +files: 0.369 +network: 0.367 +socket: 0.356 +risc-v: 0.322 +performance: 0.315 +boot: 0.303 +virtual: 0.252 +vnc: 0.251 +permissions: 0.246 +graphic: 0.236 +debug: 0.226 +arm: 0.215 +mistranslation: 0.196 +user-level: 0.196 +TCG: 0.164 +hypervisor: 0.151 +VMM: 0.151 +peripherals: 0.114 +KVM: 0.008 +-------------------- +x86: 0.996 +debug: 0.929 +i386: 0.906 +virtual: 0.269 +assembly: 0.120 +files: 0.033 +kernel: 0.017 +hypervisor: 0.016 +semantic: 0.012 +PID: 0.010 +user-level: 0.007 +architecture: 0.007 +performance: 0.007 +network: 0.006 +graphic: 0.005 +TCG: 0.004 +register: 0.004 +socket: 0.002 +device: 0.002 +boot: 0.002 +VMM: 0.001 +ppc: 0.001 +permissions: 0.001 +KVM: 0.001 +peripherals: 0.001 +vnc: 0.000 +mistranslation: 0.000 +risc-v: 0.000 +arm: 0.000 + +x86: retf or iret pagefault sets wrong error code + +With a x86_64 or i386 guest, non-KVM, when trying to execute a +"iret/iretq/retf" instruction in userspace with invalid stack pointer +(under a protected mode OS, like Linux), wrong bits are set in the +pushed error code; bit 2 is not set, indicating the error comes from +kernel space. + +If the guest OS is using this flag to decide whether this was a kernel +or user page fault, it will mistakenly decide a kernel has irrecoverably +faulted, possibly causing guest OS panic. + + +How to reproduce the problem a guest (non-KVM) Linux: +Note, on recent Linux kernel version, this needs a CPU with SMAP support +(eg. -cpu max) + +$ cat tst.c +int main() +{ +__asm__ volatile ( +"mov $0,%esp\n" +"retf" +); +return 0; +} + +$ gcc tst.c +$ ./a.out +Killed + + +"dmesg" shows the kernel has in fact triggered a "BUG: unable to handle +kernel NULL pointer dereference...", but it has "recovered" by killing +the faulting process (see attached screenshot). + + +Using self-compiled qemu from git: +commit 532cc6da74ec25b5ba6893b5757c977d54582949 (HEAD -> master, tag: v4.0.0-rc3, origin/master, origin/HEAD) +Author: Peter Maydell <email address hidden> +Date: Wed Apr 10 15:38:59 2019 +0100 + + Update version for v4.0.0-rc3 release + + Signed-off-by: Peter Maydell <email address hidden> + + + +This appears to be similar to https://bugs.launchpad.net/qemu/+bug/1866892 (and much simpler) + + +This is an automated cleanup. This bug report has been moved to QEMU's +new bug tracker on gitlab.com and thus gets marked as 'expired' now. +Please continue with the discussion here: + + https://gitlab.com/qemu-project/qemu/-/issues/265 + + |