Vigil@nce: Linux kernel, memory reading via OCFS2
April 2011 by Vigil@nce
This bulletin was written by Vigil@nce : http://vigilance.fr/
SYNTHESIS OF THE VULNERABILITY
A local attacker can write and then read from an OCFS2 filesystem, in order to obtain fragments of kernel memory.
Creation date: 12/04/2011
DESCRIPTION OF THE VULNERABILITY
Since its version 2.6.16, the Linux kernel supports the OCFS2 filesystem (Oracle Cluster File System).
A user can call the write() function to write in a file, then he can call lseek() to go after the end of the file, and then he can write again. The file area between the two writes should be filled with zeros. However, the ocfs2_prepare_page_for_write() function of the fs/ocfs2/aops.c file does not initialize the memory area.
A local attacker can therefore write and then read from an OCFS2 filesystem, in order to obtain fragments of kernel memory.
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