The patch titled
Subject: include/linux: provide a safe version of container_of()
has been added to the -mm tree. Its filename is
include-linux-provide-a-safe-version-of-container_of.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/include-linux-provide-a-safe-version-of-container_of.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/include-linux-provide-a-safe-version-of-container_of.patch
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------------------------------------------------------
From: Alexander Potapenko <glider@xxxxxxxxxx>
Subject: include/linux: provide a safe version of container_of()
Patch series "Clang: avoid undefined behavior in llist iterators":
This patchset fixes problems with pointer arithmetics overflow in llist
iterators, llist_for_each_entry() and llist_for_each_entry_safe(). Clang
turns those macros into infinite loops, because they're operating with
"negative" pointers.
As a follow-up it may make sense to convert other uses of llist_entry() to
llist_entry_safe(), or even replace uses of container_of() with
container_of_safe().
This patch (of 2):
Some code relies on "negative" (i.e. too big) pointer values being
returned by container_of() when its first argument is NULL. But doing so
breaks the compiler's assumptions that pointer arithmetic never overflows.
container_of_safe() checks its arguments and returns NULL in the case the
member offset within the container is greater than the pointer to the
member, otherwise it returns the result of container_of().
Link: http://lkml.kernel.org/r/1474636978-41435-2-git-send-email-glider@xxxxxxxxxx
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Kostya Serebryany <kcc@xxxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/kernel.h | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff -puN include/linux/kernel.h~include-linux-provide-a-safe-version-of-container_of include/linux/kernel.h
--- a/include/linux/kernel.h~include-linux-provide-a-safe-version-of-container_of
+++ a/include/linux/kernel.h
@@ -839,6 +839,21 @@ static inline void ftrace_dump(enum ftra
const typeof( ((type *)0)->member ) *__mptr = (ptr); \
(type *)( (char *)__mptr - offsetof(type,member) );})
+/**
+ * container_of_safe - safe version of container_of
+ * @ptr: the pointer to the member.
+ * @type: the type of the container struct this is embedded in.
+ * @member: the name of the member within the struct.
+ *
+ * In the case the value of @ptr is smaller than the offset of @member within
+ * @type, return 0.
+ */
+#define container_of_safe(ptr, type, member) ({ \
+ const typeof( ((type *)0)->member ) *__mptr = (ptr); \
+ (size_t)__mptr >= offsetof(type,member) ? \
+ (type *)( (char *)__mptr - offsetof(type,member) ) : (type *)0 ;})
+
+
/* Rebuild everything on CONFIG_FTRACE_MCOUNT_RECORD */
#ifdef CONFIG_FTRACE_MCOUNT_RECORD
# define REBUILD_DUE_TO_FTRACE_MCOUNT_RECORD
_
Patches currently in -mm which might be from glider@xxxxxxxxxx are
include-linux-provide-a-safe-version-of-container_of.patch
llist-introduce-llist_entry_safe.patch
kcov-do-not-instrument-lib-stackdepotc.patch
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