From: Sakari Ailus <sakari.ailus@linux.intel.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-kernel@vger.kernel.org,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
"Rafael J. Wysocki" <rafael@kernel.org>,
David Laight <David.Laight@ACULAB.COM>
Subject: [PATCH 1/1] linux/container_of.h: Warn about loss of constness
Date: Mon, 24 Oct 2022 11:26:10 +0300 [thread overview]
Message-ID: <20221024082610.74990-1-sakari.ailus@linux.intel.com> (raw)
container_of() casts the original type to another which leads to the loss
of the const qualifier if it is not specified in the caller-provided type.
This easily leads to container_of() returning a non-const pointer to a
const struct which the C compiler does not warn about.
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
---
include/linux/container_of.h | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/include/linux/container_of.h b/include/linux/container_of.h
index 2f4944b791b81..c7c21d0f41a87 100644
--- a/include/linux/container_of.h
+++ b/include/linux/container_of.h
@@ -13,6 +13,10 @@
* @type: the type of the container struct this is embedded in.
* @member: the name of the member within the struct.
*
+ * WARNING: as container_of() casts the given struct to another, also the
+ * possible const qualifier of @ptr is lost unless it is also specified in
+ * @type. This is not a problem if the containing object is not const. Use with
+ * care.
*/
#define container_of(ptr, type, member) ({ \
void *__mptr = (void *)(ptr); \
@@ -27,6 +31,11 @@
* @type: the type of the container struct this is embedded in.
* @member: the name of the member within the struct.
*
+ * WARNING: as container_of() casts the given struct to another, also the
+ * possible const qualifier of @ptr is lost unless it is also specified in
+ * @type. This is not a problem if the containing object is not const. Use with
+ * care.
+ *
* If IS_ERR_OR_NULL(ptr), ptr is returned unchanged.
*/
#define container_of_safe(ptr, type, member) ({ \
--
2.30.2
next reply other threads:[~2022-10-24 8:27 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-24 8:26 Sakari Ailus [this message]
2022-10-24 8:43 ` [PATCH 1/1] linux/container_of.h: Warn about loss of constness Greg Kroah-Hartman
2022-10-24 8:45 ` Greg Kroah-Hartman
2022-10-24 9:00 ` Andy Shevchenko
2022-10-24 17:39 ` Kees Cook
2022-10-24 17:51 ` Rafael J. Wysocki
2022-10-24 21:24 ` David Laight
2022-10-25 7:47 ` Greg Kroah-Hartman
2022-10-24 9:11 ` Sakari Ailus
2022-10-24 9:22 ` Andy Shevchenko
2022-10-24 9:34 ` David Laight
2022-10-24 9:37 ` 'Andy Shevchenko'
2022-10-24 9:46 ` David Laight
2022-10-24 10:01 ` Greg Kroah-Hartman
2022-10-24 10:05 ` David Laight
2022-10-24 9:48 ` Greg Kroah-Hartman
2022-10-24 10:07 ` Sakari Ailus
2022-10-24 8:59 ` David Laight
2022-10-24 10:11 ` Sakari Ailus
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