x86/uaccess, sched/preempt: Verify access_ok() context
I recently encountered wreckage because access_ok() was used where it
should not be, add an explicit WARN when access_ok() is used wrongly.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index faf3687..ea14831 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -68,6 +68,12 @@ static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, un
__chk_range_not_ok((unsigned long __force)(addr), size, limit); \
})
+#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
+# define WARN_ON_IN_IRQ() WARN_ON_ONCE(!in_task())
+#else
+# define WARN_ON_IN_IRQ()
+#endif
+
/**
* access_ok: - Checks if a user space pointer is valid
* @type: Type of access: %VERIFY_READ or %VERIFY_WRITE. Note that
@@ -88,8 +94,11 @@ static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, un
* checks that the pointer is in the user space range - after calling
* this function, memory access functions may still return -EFAULT.
*/
-#define access_ok(type, addr, size) \
- likely(!__range_not_ok(addr, size, user_addr_max()))
+#define access_ok(type, addr, size) \
+({ \
+ WARN_ON_IN_IRQ(); \
+ likely(!__range_not_ok(addr, size, user_addr_max())); \
+})
/*
* These are the main single-value transfer routines. They automatically
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index 75e4e30..7eeceac 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -65,19 +65,24 @@
/*
* Are we doing bottom half or hardware interrupt processing?
- * Are we in a softirq context? Interrupt context?
- * in_softirq - Are we currently processing softirq or have bh disabled?
- * in_serving_softirq - Are we currently processing softirq?
+ *
+ * in_irq() - We're in (hard) IRQ context
+ * in_softirq() - We have BH disabled, or are processing softirqs
+ * in_interrupt() - We're in NMI,IRQ,SoftIRQ context or have BH disabled
+ * in_serving_softirq() - We're in softirq context
+ * in_nmi() - We're in NMI context
+ * in_task() - We're in task context
+ *
+ * Note: due to the BH disabled confusion: in_softirq(),in_interrupt() really
+ * should not be used in new code.
*/
#define in_irq() (hardirq_count())
#define in_softirq() (softirq_count())
#define in_interrupt() (irq_count())
#define in_serving_softirq() (softirq_count() & SOFTIRQ_OFFSET)
-
-/*
- * Are we in NMI context?
- */
-#define in_nmi() (preempt_count() & NMI_MASK)
+#define in_nmi() (preempt_count() & NMI_MASK)
+#define in_task() (!(preempt_count() & \
+ (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
/*
* The preempt_count offset after preempt_disable();
