-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Update to the issue:
* Although first observed with virtual-8086 mode, the bug is not specific to virtual-8086 mode, it can be triggered with normal x86 userspace code also, even with better reproducibility. * Ben Hutchings looked at the Debian bug report [1], he failed to reproduce on his hardware, so it might be specific to some CPU models (currently my AMD E-350 is only machine known to be affected). * When deactivating mmap_min_addr, the NULL-dereferences during task-switch is exploitable, works both on native hardware and within VirtualBox. See [2] for POC to gain root privileges. * It seems, that when changing the FPU control word with "fstcw" just before exit of the process, then another process could suffer when doing __do_switch, probably related to the xsave instruction and a x86 processor bug workaround, see "noxsave" switch [3]: [BUGS=X86] Disables x86 extended register state save and restore using xsave. The kernel will fallback to enabling legacy floating-point and sse state. hd [1] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=733551 [2] http://www.halfdog.net/Security/2013/Vm86SyscallTaskSwitchKernelPanic/ [3] https://www.kernel.org/doc/Documentation/kernel-parameters.txt - -- http://www.halfdog.net/ PGP: 156A AE98 B91F 0114 FE88 2BD8 C459 9386 feed a bee -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iEYEARECAAYFAlLNAjEACgkQxFmThv7tq+44FACfeDHQHK71+7tZawm9Ftjw7Hvp j04AmwY04UwG9clERS3e1HisM2swbo1i =KoQL -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/