x86/uaccess: Allow access_ok() in irq context if pagefault_disabled

WARN_ON_IN_IRQ() assumes that the access_ok() and following
user memory access can sleep. But this assumption is not
always correct; when the pagefault is disabled, following
memory access will just returns -EFAULT and never sleep.

Add pagefault_disabled() check in WARN_ON_ONCE() so that
it can ignore the case we call it with disabling pagefault.
For this purpose, this modified pagefault_disabled() as
an inline function.

Link: http://lkml.kernel.org/r/155789868664.26965.7932665824135793317.stgit@devnote2
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index c82abd6e4ca39ad7e5d8c3ae454fc5d7a8671da3..9c4435307ff89b92dde662b5d0d4adb31cb9f220 100644 (file)
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -66,7 +66,9 @@ static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, un
 })
 
 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
-# define WARN_ON_IN_IRQ()      WARN_ON_ONCE(!in_task())
+static inline bool pagefault_disabled(void);
+# define WARN_ON_IN_IRQ()      \
+       WARN_ON_ONCE(!in_task() && !pagefault_disabled())
 #else
 # define WARN_ON_IN_IRQ()
 #endif

diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 2b70130af58578da68627927201efd1c5160900a..5a43ef7db49231259f07656bd9421b2013f9a125 100644 (file)
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -203,7 +203,10 @@ static inline void pagefault_enable(void)
 /*
  * Is the pagefault handler disabled? If so, user access methods will not sleep.
  */
-#define pagefault_disabled() (current->pagefault_disabled != 0)
+static inline bool pagefault_disabled(void)
+{
+       return current->pagefault_disabled != 0;
+}
 
 /*
  * The pagefault handler is in general disabled by pagefault_disable() or