From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-Id: <20120527002622.295343320@linuxfoundation.org> Date: Sun, 27 May 2012 09:27:07 +0900 From: Greg KH To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Catalin Marinas , Dima Zavin , John Stultz , Will Deacon , Russell King Subject: [ 54/55] ARM: 7409/1: Do not call flush_cache_user_range with mmap_sem held In-Reply-To: <20120527005203.GA2146@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dima Zavin commit 435a7ef52db7d86e67a009b36cac1457f8972391 upstream. We can't be holding the mmap_sem while calling flush_cache_user_range because the flush can fault. If we fault on a user address, the page fault handler will try to take mmap_sem again. Since both places acquire the read lock, most of the time it succeeds. However, if another thread tries to acquire the write lock on the mmap_sem (e.g. mmap) in between the call to flush_cache_user_range and the fault, the down_read in do_page_fault will deadlock. [will: removed drop of vma parameter as already queued by rmk (7365/1)] Acked-by: Catalin Marinas Signed-off-by: Dima Zavin Signed-off-by: John Stultz Signed-off-by: Will Deacon Signed-off-by: Russell King Signed-off-by: Greg Kroah-Hartman --- arch/arm/kernel/traps.c | 2 ++ 1 file changed, 2 insertions(+) --- a/arch/arm/kernel/traps.c +++ b/arch/arm/kernel/traps.c @@ -451,7 +451,9 @@ do_cache_op(unsigned long start, unsigne if (end > vma->vm_end) end = vma->vm_end; + up_read(&mm->mmap_sem); flush_cache_user_range(start, end); + return; } up_read(&mm->mmap_sem); }