3.2-stable review patch. If anyone has any objections, please let me know.
------------------
From: Dima Zavin <d...@android.com>
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 <catalin.mari...@arm.com>
Signed-off-by: Dima Zavin <d...@android.com>
Signed-off-by: John Stultz <john.stu...@linaro.org>
Signed-off-by: Will Deacon <will.dea...@arm.com>
Signed-off-by: Russell King <rmk+ker...@arm.linux.org.uk>
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
arch/arm/kernel/traps.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 55b2f3d..63d402f 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -496,7 +496,9 @@ do_cache_op(unsigned long start, unsigned long end, int
flags)
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 majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
