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Message-ID: <87fxp4pi0r.fsf_-_@skyscraper.fehenstaub.lan>
Date: Sun, 17 Aug 2008 03:06:12 +0200
From: Johannes Weiner <hannes@...urebad.de>
To: Hugh Dickins <hugh@...itas.com>
Cc: "Rafael J. Wysocki" <rjw@...k.pl>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Kernel Testers List <kernel-testers@...r.kernel.org>,
Randy Dunlap <randy.dunlap@...cle.com>
Subject: [PATCH] mm: make unmap_vmas() handle non-page-aligned boundary addresses
zap_pte_range() overruns the page tables if the distance between the
start and end is not a multiple of the pagesize. Because then,
`start' will never be equal to `end' and we will keep looping.
To fix this, round the boundary addresses to exclude partial pages from
the range completely, we must not unmap them anyway.
Signed-off-by: Johannes Weiner <hannes@...urebad.de>
---
Hugh Dickins <hugh@...itas.com> writes:
> On Sat, 16 Aug 2008, Rafael J. Wysocki wrote:
>>
>> Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=11335
>> Subject : 2.6.27-rc2-git5 BUG: unable to handle kernel paging request
>> Submitter : Randy Dunlap <randy.dunlap@...cle.com>
>> Date : 2008-08-12 4:18 (5 days old)
>> References : http://marc.info/?l=linux-kernel&m=121851477201960&w=4
>> Handled-By : Hugh Dickins <hugh@...itas.com>
>
> This should still be listed for now, it's interesting,
> but I doubt we'll make any progress unless it can be reproduced.
I think this patch fixes it. exit_mmap() even calls unmap_vmas() with
an ending address of -1UL which is not page-aligned in my book and on my
architecture :)
It is a similar problem to what we had with gup some weeks ago.
diff --git a/mm/memory.c b/mm/memory.c
index 1002f47..483c5d0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -896,11 +896,17 @@ unsigned long unmap_vmas(struct mmu_gather **tlbp,
long zap_work = ZAP_BLOCK_SIZE;
unsigned long tlb_start = 0; /* For tlb_finish_mmu */
int tlb_start_valid = 0;
- unsigned long start = start_addr;
+ unsigned long start;
spinlock_t *i_mmap_lock = details? details->i_mmap_lock: NULL;
int fullmm = (*tlbp)->fullmm;
struct mm_struct *mm = vma->vm_mm;
+ /* Preserve partial pages */
+ start_addr = PAGE_ALIGN(start_addr);
+ end_addr &= PAGE_MASK;
+
+ start = start_addr;
+
mmu_notifier_invalidate_range_start(mm, start_addr, end_addr);
for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next) {
unsigned long end;
--
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