linux-kernel - [PATCH v6 2/9] dax: alloc_dax() return ERR_PTR(-EOPNOTSUPP) for CONFIG

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20240215144633.96437-3-mathieu.desnoyers@efficios.com>
Date: Thu, 15 Feb 2024 09:46:26 -0500
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Dan Williams <dan.j.williams@...el.com>,
	Arnd Bergmann <arnd@...db.de>,
	Dave Chinner <david@...morbit.com>
Cc: linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Vishal Verma <vishal.l.verma@...el.com>,
	Dave Jiang <dave.jiang@...el.com>,
	Matthew Wilcox <willy@...radead.org>,
	Russell King <linux@...linux.org.uk>,
	linux-arch@...r.kernel.org,
	linux-cxl@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org,
	linux-xfs@...r.kernel.org,
	dm-devel@...ts.linux.dev,
	nvdimm@...ts.linux.dev,
	linux-s390@...r.kernel.org
Subject: [PATCH v6 2/9] dax: alloc_dax() return ERR_PTR(-EOPNOTSUPP) for CONFIG_DAX=n

Change the return value from NULL to PTR_ERR(-EOPNOTSUPP) for
CONFIG_DAX=n to be consistent with the fact that CONFIG_DAX=y
never returns NULL.

This is done in preparation for using cpu_dcache_is_aliasing() in a
following change which will properly support architectures which detect
data cache aliasing at runtime.

Fixes: 4e4ced93794a ("dax: Move mandatory ->zero_page_range() check in alloc_dax()")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Reviewed-by: Dan Williams <dan.j.williams@...el.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Vishal Verma <vishal.l.verma@...el.com>
Cc: Dave Jiang <dave.jiang@...el.com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Russell King <linux@...linux.org.uk>
Cc: linux-arch@...r.kernel.org
Cc: linux-cxl@...r.kernel.org
Cc: linux-fsdevel@...r.kernel.org
Cc: linux-mm@...ck.org
Cc: linux-xfs@...r.kernel.org
Cc: dm-devel@...ts.linux.dev
Cc: nvdimm@...ts.linux.dev
---
 drivers/dax/super.c | 5 +++++
 include/linux/dax.h | 6 +-----
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 0da9232ea175..205b888d45bf 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -319,6 +319,11 @@ EXPORT_SYMBOL_GPL(dax_alive);
  * that any fault handlers or operations that might have seen
  * dax_alive(), have completed.  Any operations that start after
  * synchronize_srcu() has run will abort upon seeing !dax_alive().
+ *
+ * Note, because alloc_dax() returns an ERR_PTR() on error, callers
+ * typically store its result into a local variable in order to check
+ * the result. Therefore, care must be taken to populate the struct
+ * device dax_dev field make sure the dax_dev is not leaked.
  */
 void kill_dax(struct dax_device *dax_dev)
 {
diff --git a/include/linux/dax.h b/include/linux/dax.h
index e3ffe7c7f01d..9d3e3327af4c 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -88,11 +88,7 @@ static inline void *dax_holder(struct dax_device *dax_dev)
 static inline struct dax_device *alloc_dax(void *private,
 		const struct dax_operations *ops)
 {
-	/*
-	 * Callers should check IS_ENABLED(CONFIG_DAX) to know if this
-	 * NULL is an error or expected.
-	 */
-	return NULL;
+	return ERR_PTR(-EOPNOTSUPP);
 }
 static inline void put_dax(struct dax_device *dax_dev)
 {
-- 
2.39.2