CVE-2018-12126: Infoleak

First published: Tue Nov 06 2018(Updated: )

A flaw was found in many Intel microprocessor designs related to possible information leak of the processor store buffer structure which contains recent stores (writes) to memory.. Modern Intel microprocessors implement hardware-level micro-optimizations to improve the performance of writing data back to CPU caches. The write operation is split into STA (STore Address) and STD (STore Data) sub-operations. These sub-operations allow the processor to hand-off address generation logic into these sub-operations for optimized writes. Both of these sub-operations write to a shared distributed processor structure called the 'processor store buffer'. The processor store buffer is conceptually a table of address, value, and 'is valid' entries. As the sub-operations can execute independently of each other, they can each update the address, and/or value columns of the table independently. This means that at different points in time the address or value may be invalid. The processor may speculatively forward entries from the store buffer. The split design used allows for such forwarding to speculatively use stale values, such as the wrong address, returning data from a previous unrelated store. Since this only occurs for loads that will be reissued following the fault/assist resolution, the program is not architecturally impacted, but store buffer state can be leaked to malicious code carefully crafted to retrieve this data via side-channel analysis. The processor store buffer entries are equally divided between the number of active Hyper-Threads. Conditions such as power-state change can reallocate the processor store buffer entries in a half-updated state to another thread without ensuring that the entries have been cleared. Additional information: <a href="https://access.redhat.com/security/vulnerabilities/mds">https://access.redhat.com/security/vulnerabilities/mds</a> Upstream fixes: <a href="https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fa4bff165070dc40a3de35b78e4f8da8e8d85ec5">https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fa4bff165070dc40a3de35b78e4f8da8e8d85ec5</a> Intel Advisory: <a href="https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00233.html">https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00233.html</a>

Credit: Ke Sun Henrique Kawakami Kekai Hu Rodrigo Branco IntelYuval Yarom University of AdelaideBrandon Falk Microsoft Windows Platform Security TeamGiorgi Maisuradze Microsoft ResearchMichael Schwarz Daniel Gruss Graz University of TechnologyAlyssa Milburn Sebastian Osterlund Pietro Frigo Kaveh Razavi Herbert Bos Cristiano Giuffrida VUSec group at VU AmsterdamDan Horea Lutas BitDefenderMoritz Lipp secure@intel.com

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