3.3-stable review patch. If anyone has any objections, please let me know.
------------------ From: Dima Zavin <[email protected]> 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 <[email protected]> Signed-off-by: Dima Zavin <[email protected]> Signed-off-by: John Stultz <[email protected]> Signed-off-by: Will Deacon <[email protected]> Signed-off-by: Russell King <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/arm/kernel/traps.c | 2 ++ 1 file changed, 2 insertions(+) --- a/arch/arm/kernel/traps.c +++ b/arch/arm/kernel/traps.c @@ -491,7 +491,9 @@ 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); } -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
