From: Martin Schwidefsky <schwidefsky@de.ibm.com>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc: Matt Mackall <mpm@selenic.com>,
Gerald Schaefer <gerald.schaefer@de.ibm.com>,
akpm@linux-foundation.org
Subject: [PATCH] acquire mmap semaphore in pagemap_read.
Date: Thu, 12 Mar 2009 11:33:08 +0100 [thread overview]
Message-ID: <20090312113308.6fe18a93@skybase> (raw)
From: Martin Schwidefsky <schwidefsky@de.ibm.com>
The walk_page_range function may only be called while holding the mmap
semaphore. Otherwise a concurrent munmap could free a page table that
is read by the generic page table walker.
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
fs/proc/task_mmu.c | 2 ++
1 file changed, 2 insertions(+)
diff -urpN linux-2.6/fs/proc/task_mmu.c linux-2.6-patched/fs/proc/task_mmu.c
--- linux-2.6/fs/proc/task_mmu.c 2009-03-12 11:32:51.000000000 +0100
+++ linux-2.6-patched/fs/proc/task_mmu.c 2009-03-12 11:33:16.000000000 +0100
@@ -716,7 +716,9 @@ static ssize_t pagemap_read(struct file
* user buffer is tracked in "pm", and the walk
* will stop when we hit the end of the buffer.
*/
+ down_read(&mm->mmap_sem);
ret = walk_page_range(start_vaddr, end_vaddr, &pagemap_walk);
+ up_read(&mm->mmap_sem);
if (ret == PM_END_OF_BUFFER)
ret = 0;
/* don't need mmap_sem for these, but this looks cleaner */
--
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next reply other threads:[~2009-03-12 10:36 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-12 10:33 Martin Schwidefsky [this message]
2009-03-12 11:45 ` [PATCH] acquire mmap semaphore in pagemap_read Alexey Dobriyan
2009-03-12 11:54 ` Martin Schwidefsky
2009-03-12 15:23 ` Matt Mackall
2009-03-12 15:27 ` Martin Schwidefsky
2009-03-12 15:41 ` Brice Goglin
2009-03-12 15:46 ` Martin Schwidefsky
2009-03-12 15:54 ` Martin Schwidefsky
2009-03-17 12:04 ` Martin Schwidefsky
2009-03-17 16:21 ` Matt Mackall
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