ARM: Tighten check for allowable CPSR values

Reviewed-by: Arve Hjønnevåg <arve@android.com>
Acked-by: Dima Zavin <dima@android.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 13 insertions, 4 deletions

diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h
index c974be8913a7..7ce15eb15f72 100644
--- a/arch/arm/include/asm/ptrace.h
+++ b/arch/arm/include/asm/ptrace.h
@@ -158,15 +158,24 @@ 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;