Date: Thu, 18 Dec 2014 11:35:01 -0800 From: Andy Lutomirski <luto@...capital.net> To: oss-security@...ts.openwall.com Subject: CVE Request: Linux x86_64 userspace address leak 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. The bug is fixed here: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/arch/x86?id=f647d7c155f069c1a068030255c300663516420e There's a test case in the patch description. Note: the patch description mentions another unfixed but and has a test for that bug as well. As far as I can tell, the other bug has no security implications -- it merely allows a program to cause the kernel to replace its segment bases with predictable values during the next context switch. * It's possible that I missed something and this bug was introduced more recently. ** The attack won't work against 64-bit threads with TLS bases > 4GB, but AFAIK that's unusual. It also won't work against the small number of programs using obsolete threading libraries that point their TLS segments into the LDT. --Andy
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