lkml.org 
[lkml]   [2015]   [Jan]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 1/1] mm: pagemap: limit scan to virtual region being asked
Date
pagemap_read scans through the virtual address space of a
task till it prepares 'count' pagemaps or it reaches end
of task.

This presents a problem when the page walk doesn't happen
for vma with VM_PFNMAP set. In which case walk is silently
skipped and no pagemap is prepare, in turn making
pagemap_read to scan through task end, even crossing beyond
'count', landing into a different vma region. This leads to
wrong presentation of mappings for that vma.

Fix this by limiting end_vaddr to the end of the virtual
address region being scanned.

Signed-off-by: Shiraz Hashim <shashim@codeaurora.org>
---
fs/proc/task_mmu.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 246eae8..04362e4 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1270,7 +1270,9 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
src = *ppos;
svpfn = src / PM_ENTRY_BYTES;
start_vaddr = svpfn << PAGE_SHIFT;
- end_vaddr = TASK_SIZE_OF(task);
+ end_vaddr = start_vaddr + ((count / PM_ENTRY_BYTES) << PAGE_SHIFT);
+ if ((end_vaddr > TASK_SIZE_OF(task)) || (end_vaddr < start_vaddr))
+ end_vaddr = TASK_SIZE_OF(task);

/* watch out for wraparound */
if (svpfn > TASK_SIZE_OF(task) >> PAGE_SHIFT)
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of the Code Aurora Forum, hosted by The Linux Foundation



\
 
 \ /
  Last update: 2015-01-13 14:01    [W:0.084 / U:0.668 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site