linux-kernel - [ 120/135] ARM: 7526/1: traps: send SIGILL if get

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Message-Id: <20120917003642.815668331@decadent.org.uk>
Date:	Mon, 17 Sep 2012 01:38:25 +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, Will Deacon <will.deacon@....com>,
	Russell King <rmk+kernel@....linux.org.uk>
Subject: [ 120/135] ARM: 7526/1: traps: send SIGILL if get_user fails on undef handling
 path

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

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

From: Will Deacon <will.deacon@....com>

commit 2b2040af0b64cd93e5d4df2494c4486cf604090d upstream.

get_user may fail to load from the provided __user address due to an
unhandled fault generated by the access.

In the case of the undefined instruction trap, this results in failure
to load the faulting instruction, in which case we should send SIGILL to
the task rather than continue with potentially uninitialised data.

Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/arm/kernel/traps.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index f794521..b0179b8 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -420,20 +420,23 @@ asmlinkage void __exception do_undefinstr(struct pt_regs *regs)
 #endif
 			instr = *(u32 *) pc;
 	} else if (thumb_mode(regs)) {
-		get_user(instr, (u16 __user *)pc);
+		if (get_user(instr, (u16 __user *)pc))
+			goto die_sig;
 		if (is_wide_instruction(instr)) {
 			unsigned int instr2;
-			get_user(instr2, (u16 __user *)pc+1);
+			if (get_user(instr2, (u16 __user *)pc+1))
+				goto die_sig;
 			instr <<= 16;
 			instr |= instr2;
 		}
-	} else {
-		get_user(instr, (u32 __user *)pc);
+	} else if (get_user(instr, (u32 __user *)pc)) {
+		goto die_sig;
 	}
 
 	if (call_undef_hook(regs, instr) == 0)
 		return;
 
+die_sig:
 #ifdef CONFIG_DEBUG_USER
 	if (user_debug & UDBG_UNDEFINED) {
 		printk(KERN_INFO "%s (%d): undefined instruction: pc=%p\n",


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