[Intel-gfx] [PATCH] drm/i915: fix driver's versions of WARN_ON & WARN_ON_ONCE

[Dave Gordon]

The current versions of these two macros don't work correctly if the
argument expression happens to contain a modulo operator (%) -- when
stringified, it gets interpreted as a printf formatting character!
With a specifically crafted parameter, this could probably cause a
kernel OOPS; consider WARN_ON(p%s) or WARN_ON(f %*pEp).

Instead, we should use an explicit "%s" format, with the stringified
expression as the coresponding literal-string argument.

Signed-off-by: Dave Gordon <david.s.gordon at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index b157865..674b223 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -67,11 +67,11 @@
 		BUILD_BUG_ON(__i915_warn_cond); \
 	WARN(__i915_warn_cond, "WARN_ON(" #x ")"); })
 #else
-#define WARN_ON(x) WARN((x), "WARN_ON(" #x ")")
+#define WARN_ON(x) WARN((x), "WARN_ON(%s)", #x )
 #endif
 
 #undef WARN_ON_ONCE
-#define WARN_ON_ONCE(x) WARN_ONCE((x), "WARN_ON_ONCE(" #x ")")
+#define WARN_ON_ONCE(x) WARN_ONCE((x), "WARN_ON_ONCE(%s)", #x )
 
 #define MISSING_CASE(x) WARN(1, "Missing switch case (%lu) in %s\n", \
 			     (long) (x), __func__);
-- 
1.9.1