From: "Stephen C. Tweedie" <sct@redhat.com>
To: Kanoj Sarcar <kanoj@google.engr.sgi.com>,
Linus Torvalds <torvalds@transmeta.com>,
Alan Cox <number6@the-village.bc.nu>
Cc: Linux-MM@kvack.org, linux-kernel@vger.rutgers.edu
Subject: Patch: Re: boundary condition bug fix for vmalloc()
Date: Thu, 22 Apr 1999 16:30:01 +0100 (BST) [thread overview]
Message-ID: <14111.16505.189611.184633@dukat.scot.redhat.com> (raw)
In-Reply-To: <199904220012.RAA57724@google.engr.sgi.com>
Hi,
On Wed, 21 Apr 1999 17:12:37 -0700 (PDT), kanoj@google.engr.sgi.com
(Kanoj Sarcar) said:
> Under heavy load conditions, get_vm_area() might end up allocating an
> address range beyond VMALLOC_END. The problem is after the for loop in
> get_vm_area() terminates, no consistency check (addr > VMALLOC_END -
> size) is performed on the "addr".
Agreed, and the patch looks OK. Moving the test outside the for loop
entirely has the same effect while shaving a few cycles off the
function. The existing clearly broken in not checking the size of the
final area if we ran off the end of the vm_area chain.
--Stephen
----------------------------------------------------------------
--- mm/vmalloc.c~ Mon Jan 18 18:19:28 1999
+++ mm/vmalloc.c Thu Apr 22 16:12:58 1999
@@ -161,11 +161,11 @@
for (p = &vmlist; (tmp = *p) ; p = &tmp->next) {
if (size + addr < (unsigned long) tmp->addr)
break;
- if (addr > VMALLOC_END-size) {
- kfree(area);
- return NULL;
- }
addr = tmp->size + (unsigned long) tmp->addr;
+ }
+ if (addr > VMALLOC_END-size) {
+ kfree(area);
+ return NULL;
}
area->addr = (void *)addr;
area->size = size + PAGE_SIZE;
----------------------------------------------------------------
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prev parent reply other threads:[~1999-04-22 15:30 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-04-22 0:12 boundary condition bug fix for vmalloc() Kanoj Sarcar
1999-04-22 15:30 ` Stephen C. Tweedie [this message]
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