linux-kernel - [ 61/70] m68k: Make sys_atomic_cmpxchg

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Message-Id: <20120807032804.958167326@decadent.org.uk>
Date:	Tue, 07 Aug 2012 04:28:56 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Andreas Schwab <schwab@...ux-m68k.org>,
	Thorsten Glaser <tg@...ian.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: [ 61/70] m68k: Make sys_atomic_cmpxchg_32 work on classic m68k

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andreas Schwab <schwab@...ux-m68k.org>

commit 9e2760d18b3cf179534bbc27692c84879c61b97c upstream.

User space access must always go through uaccess accessors, since on
classic m68k user space and kernel space are completely separate.

Signed-off-by: Andreas Schwab <schwab@...ux-m68k.org>
Tested-by: Thorsten Glaser <tg@...ian.org>
Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/m68k/kernel/sys_m68k.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/m68k/kernel/sys_m68k.c b/arch/m68k/kernel/sys_m68k.c
index 8623f8d..9a5932e 100644
--- a/arch/m68k/kernel/sys_m68k.c
+++ b/arch/m68k/kernel/sys_m68k.c
@@ -479,9 +479,13 @@ sys_atomic_cmpxchg_32(unsigned long newval, int oldval, int d3, int d4, int d5,
 			goto bad_access;
 		}
 
-		mem_value = *mem;
+		/*
+		 * No need to check for EFAULT; we know that the page is
+		 * present and writable.
+		 */
+		__get_user(mem_value, mem);
 		if (mem_value == oldval)
-			*mem = newval;
+			__put_user(newval, mem);
 
 		pte_unmap_unlock(pte, ptl);
 		up_read(&mm->mmap_sem);


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