linux-kernel - [17/59] ARM: Tighten check for allowable CPSR values

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Message-Id: <20100824222523.888166392@clark.site>
Date:	Tue, 24 Aug 2010 15:24:29 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Dima Zavin <dima@...roid.com>,
	Russell King <rmk+kernel@....linux.org.uk>
Subject: [17/59] ARM: Tighten check for allowable CPSR values

2.6.32-stable review patch.  If anyone has any objections, please let us know.

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

From: Russell King <rmk+kernel@....linux.org.uk>

commit 41e2e8fd34fff909a0e40129f6ac4233ecfa67a9 upstream.

Reviewed-by: Arve Hjønnevåg <arve@...roid.com>
Acked-by: Dima Zavin <dima@...roid.com>
Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 arch/arm/include/asm/ptrace.h |   17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

--- a/arch/arm/include/asm/ptrace.h
+++ b/arch/arm/include/asm/ptrace.h
@@ -150,15 +150,24 @@ struct pt_regs {
  */
 static inline int valid_user_regs(struct pt_regs *regs)
 {
-	if (user_mode(regs) && (regs->ARM_cpsr & PSR_I_BIT) == 0) {
-		regs->ARM_cpsr &= ~(PSR_F_BIT | PSR_A_BIT);
-		return 1;
+	unsigned long mode = regs->ARM_cpsr & MODE_MASK;
+
+	/*
+	 * Always clear the F (FIQ) and A (delayed abort) bits
+	 */
+	regs->ARM_cpsr &= ~(PSR_F_BIT | PSR_A_BIT);
+
+	if ((regs->ARM_cpsr & PSR_I_BIT) == 0) {
+		if (mode == USR_MODE)
+			return 1;
+		if (elf_hwcap & HWCAP_26BIT && mode == USR26_MODE)
+			return 1;
 	}
 
 	/*
 	 * Force CPSR to something logical...
 	 */
-	regs->ARM_cpsr &= PSR_f | PSR_s | (PSR_x & ~PSR_A_BIT) | PSR_T_BIT | MODE32_BIT;
+	regs->ARM_cpsr &= PSR_f | PSR_s | PSR_x | PSR_T_BIT | MODE32_BIT;
 	if (!(elf_hwcap & HWCAP_26BIT))
 		regs->ARM_cpsr |= USR_MODE;
 


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