[PATCH 1/6] ERR_PTR: if errno value is known at compile time, make sure it's valid

[Marcin Slusarz]

ERR_PTR is easy to call with wrong argument (positive errno),
and this error lead to catastrophic event - oops or kernel panic
(dereference of invalid pointer).

As most of error handling code paths are rarely tested, this kind of
bug can be hidden for years.

(Currently there are > 1400 calls of ERR_PTR with constant argument.)

Signed-off-by: Marcin Slusarz <marcin.slusarz@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
 include/linux/err.h |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/include/linux/err.h b/include/linux/err.h
index ec87f31..7b5daa6 100644
--- a/include/linux/err.h
+++ b/include/linux/err.h
@@ -19,11 +19,13 @@
 
 #define IS_ERR_VALUE(x) unlikely((x) >= (unsigned long)-MAX_ERRNO)
 
-static inline void *ERR_PTR(long error)
+static inline void *__ERR_PTR(long error)
 {
 	return (void *) error;
 }
 
+#define ERR_PTR(error) (BUILD_BUG_ON(__builtin_constant_p(error) && !IS_ERR_VALUE(error)), __ERR_PTR(error))
+
 static inline long PTR_ERR(const void *ptr)
 {
 	return (long) ptr;
-- 
1.5.4.5

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