Messages in this thread Patch in this message | | | From | Mitsuo Hayasaka <> | Subject | [PATCH] avoid null pointer access in vm_struct | Date | Wed, 17 Aug 2011 22:28:48 +0900 |
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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, which results in a null pointer access and leads to a kernel panic.
Why this happen: For example, in __vmalloc_area_node, the nr_pages field of vm_struct are set to the expected number of pages to be allocated, before the actual pages allocations. 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.
Patch: This patch avoids accessing the pages field with unallocated page when show_numa_info() is called. So, it can solve this problem.
Signed-off-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Namhyung Kim <namhyung@gmail.com> Cc: David Rientjes <rientjes@google.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> ---
mm/vmalloc.c | 7 +++++-- 1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 7ef0903..e2ec5b0 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2472,13 +2472,16 @@ static void show_numa_info(struct seq_file *m, struct vm_struct *v) if (NUMA_BUILD) { unsigned int nr, *counters = m->private; - if (!counters) + if (!counters || !v->nr_pages || !v->pages) return; memset(counters, 0, nr_node_ids * sizeof(unsigned int)); - for (nr = 0; nr < v->nr_pages; nr++) + for (nr = 0; nr < v->nr_pages; nr++) { + if (!v->pages[nr]) + break; counters[page_to_nid(v->pages[nr])]++; + } for_each_node_state(nr, N_HIGH_MEMORY) if (counters[nr])
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