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Subject[11/90] futex: Take mmap_sem for get_user_pages in fault_in_user_writeable
2.6.31-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Andi Kleen <andi@firstfloor.org>

commit 722d0172377a5697919b9f7e5beb95165b1dec4e upstream.

get_user_pages() must be called with mmap_sem held.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Andrew Morton <akpm@linuxfoundation.org>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Darren Hart <dvhltc@us.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <20091208121942.GA21298@basil.fritz.box>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
kernel/futex.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -303,8 +303,14 @@ void put_futex_key(int fshared, union fu
*/
static int fault_in_user_writeable(u32 __user *uaddr)
{
- int ret = get_user_pages(current, current->mm, (unsigned long)uaddr,
- 1, 1, 0, NULL, NULL);
+ struct mm_struct *mm = current->mm;
+ int ret;
+
+ down_read(&mm->mmap_sem);
+ ret = get_user_pages(current, mm, (unsigned long)uaddr,
+ 1, 1, 0, NULL, NULL);
+ up_read(&mm->mmap_sem);
+
return ret < 0 ? ret : 0;
}




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