linux-kernel - [PATCH] mm: fix null vm_ops dereference in sys_remap_file

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Message-ID: <20121011101834.1793.7213.stgit@zurg>
Date:	Thu, 11 Oct 2012 14:18:34 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Cc:	Sasha Levin <levinsasha928@...il.com>
Subject: [PATCH] mm: fix null vm_ops dereference in sys_remap_file_pages

This fixes bug introduced in commit "mm: kill vma flag VM_CAN_NONLINEAR",
vma->vm_ops must be checked before checking vm_ops->remap_pages.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>
Reported-by: Sasha Levin <levinsasha928@...il.com>
---
 mm/fremap.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/fremap.c b/mm/fremap.c
index 3899a86..a0aaf0e 100644
--- a/mm/fremap.c
+++ b/mm/fremap.c
@@ -169,7 +169,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
 	if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
 		goto out;
 
-	if (!vma->vm_ops->remap_pages)
+	if (!vma->vm_ops || !vma->vm_ops->remap_pages)
 		goto out;
 
 	if (start < vma->vm_start || start + size > vma->vm_end)

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