Date: Fri, 26 Dec 2014 19:19:27 +0530 (IST) From: P J P <ppandit@...hat.com> To: oss security list <oss-security@...ts.openwall.com> cc: Andy Lutomirski <luto@...capital.net> Subject: Re: CVE Request: Linux x86_64 userspace address leak +-- On Thu, 18 Dec 2014, Andy Lutomirski wrote --+ | On all* Linux x86_64 kernels, malicious user programs can learn the | TLS base addresses of threads** that they preempt. | | In principle, this bug will allow programs to partially bypass ASLR | when attacking other user programs. Figuring out how to adapt the | test code to do that is left as an exercise to the reader. | | https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/arch/x86?id=f647d7c155f069c1a068030255c300663516420e | | ** The attack won't work against 64-bit threads with TLS bases > 4GB, | but AFAIK that's unusual. It seems to require 32bit interfaces(CONFIG_X86_32). On x86_64 Fedora/RHEL kernels, it says: === $ cat /etc/redhat-release Fedora release 21 (Twenty One) $ $ cc -xc -o estest estest.c $ cc -xc -o gsbasetest gsbasetest.c $ $ ./estest estest: set_thread_area: Function not implemented $ $ ./gsbasetest [OK] ARCH_SET_GS worked [OK] Writing 0 to gs worked [FAIL] gsbase was corrupted $ === -- Prasad J Pandit / Red Hat Product Security Team 47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F
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