From: Mitsuo Hayasaka Date: Tue, 1 Nov 2011 00:08:13 +0000 (-0700) Subject: mm: avoid null pointer access in vm_struct via /proc/vmallocinfo X-Git-Tag: v3.2-rc1~108^2~93 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f5252e009d5b87071a919221e4f6624184005368;p=pandora-kernel.git mm: avoid null pointer access in vm_struct via /proc/vmallocinfo The /proc/vmallocinfo shows information about vmalloc allocations in vmlist that is a linklist of vm_struct. It, however, may access pages field of vm_struct where a page was not allocated. This results in a null pointer access and leads to a kernel panic. Why this happens: In __vmalloc_node_range() called from vmalloc(), newly allocated vm_struct is added to vmlist at __get_vm_area_node() and then, some fields of vm_struct such as nr_pages and pages are set at __vmalloc_area_node(). In other words, it is added to vmlist before it is fully initialized. At the same time, when the /proc/vmallocinfo is read, it accesses the pages field of vm_struct according to the nr_pages field at show_numa_info(). Thus, a null pointer access happens. The patch adds the newly allocated vm_struct to the vmlist *after* it is fully initialized. So, it can avoid accessing the pages field with unallocated page when show_numa_info() is called. Signed-off-by: Mitsuo Hayasaka Cc: Andrew Morton Cc: David Rientjes Cc: Namhyung Kim Cc: "Paul E. McKenney" Cc: Jeremy Fitzhardinge Cc: Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed