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Subject[patch] mm: vmap fix overflow
This patch is appropriate for 2.6.28 too.

--

The new vmap allocator can wrap the address and get confused in the case of
large allocations or VMALLOC_END near the end of address space.

Problem reported by Christoph Hellwig on a 32-bit XFS workload.

Signed-off-by: Nick Piggin <npiggin@suse.de>
---
mm/vmalloc.c | 6 ++++++
1 file changed, 6 insertions(+)

Index: linux-2.6/mm/vmalloc.c
===================================================================
--- linux-2.6.orig/mm/vmalloc.c
+++ linux-2.6/mm/vmalloc.c
@@ -334,6 +334,9 @@ retry:
addr = ALIGN(vstart, align);

spin_lock(&vmap_area_lock);
+ if (addr + size < addr)
+ goto overflow;
+
/* XXX: could have a last_hole cache */
n = vmap_area_root.rb_node;
if (n) {
@@ -365,6 +368,8 @@ retry:

while (addr + size > first->va_start && addr + size <= vend) {
addr = ALIGN(first->va_end + PAGE_SIZE, align);
+ if (addr + size < addr)
+ goto overflow;

n = rb_next(&first->rb_node);
if (n)
@@ -375,6 +380,7 @@ retry:
}
found:
if (addr + size > vend) {
+overflow:
spin_unlock(&vmap_area_lock);
if (!purged) {
purge_vmap_area_lazy();

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