linux-kernel - [PATCH] powerpc/mm: Fix missing mmap

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Date:   Thu,  7 Sep 2017 18:25:29 +0200
From:   Laurent Dufour <laurent.du4@...e.fr>
To:     benh@...nel.crashing.org, mpe@...erman.id.au,
        linuxppc-dev@...ts.ozlabs.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] powerpc/mm: Fix missing mmap_sem release

The commit b5c8f0fd595d ("powerpc/mm: Rework mm_fault_error()") reviewed
the way the error path is managed in __do_page_fault() but it was a bit too
agressive when handling a case by returning without releasing the mmap_sem.

By the way, replacing current->mm->mmap_sem by mm->mmap_sem as mm is set to
current->mm.

Fixes: b5c8f0fd595d ("powerpc/mm: Rework mm_fault_error()")
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Signed-off-by: Laurent Dufour <laurent.du4@...e.fr>
---
 arch/powerpc/mm/fault.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 4797d08581ce..f799ccf37d27 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -521,10 +521,11 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
 		 * User mode? Just return to handle the fatal exception otherwise
 		 * return to bad_page_fault
 		 */
+		up_read(&mm->mmap_sem);
 		return is_user ? 0 : SIGBUS;
 	}
 
-	up_read(&current->mm->mmap_sem);
+	up_read(&mm->mmap_sem);
 
 	if (unlikely(fault & VM_FAULT_ERROR))
 		return mm_fault_error(regs, address, fault);
-- 
2.7.4