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Eliminate the possibility of 32-bit arithmetic overflow in the calculation

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of vm_kmem_size that may occur if the system administrator has specified a
vm.vm_kmem_size tunable value that exceeds the hard cap.

PR:		162741
Submitted by:	Adam McDougall
Reviewed by:	bde@
MFC after:	3 weeks
This commit is contained in:
Alan Cox 2011-12-07 07:03:14 +00:00
parent f769e5b0fa
commit c749c003b8
1 changed files with 4 additions and 4 deletions
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8
sys/kern/kern_malloc.c
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@ -740,11 +740,11 @@ kmeminit(void *dummy)
/* /*
* Limit kmem virtual size to twice the physical memory. * Limit kmem virtual size to twice the physical memory.
* This allows for kmem map sparseness, but limits the size * This allows for kmem map sparseness, but limits the size
* to something sane. Be careful to not overflow the 32bit * to something sane. Be careful to not overflow the 32bit
* ints while doing the check. * ints while doing the check or the adjustment.
*/ */
if (((vm_kmem_size / 2) / PAGE_SIZE) > cnt.v_page_count) if (vm_kmem_size / 2 / PAGE_SIZE > mem_size)
vm_kmem_size = 2 * cnt.v_page_count * PAGE_SIZE; vm_kmem_size = 2 * mem_size * PAGE_SIZE;
#ifdef DEBUG_MEMGUARD #ifdef DEBUG_MEMGUARD
tmp = memguard_fudge(vm_kmem_size, vm_kmem_size_max); tmp = memguard_fudge(vm_kmem_size, vm_kmem_size_max);