Date: Sun, 28 Dec 2014 07:40:51 -0800 From: Andy Lutomirski <luto@...capital.net> To: P J P <ppandit@...hat.com> Cc: oss security list <oss-security@...ts.openwall.com> Subject: Re: CVE Request: Linux x86_64 userspace address leak On Dec 26, 2014 5:49 AM, "P J P" <ppandit@...hat.com> wrote: > > +-- 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: Try building with -m32 but running on a 64-bit kernel. --Andy > > === > $ 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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