linux-kernel - [PATCH 3.12 30/82] 3w-xxxx: fix mis-aligned struct accesses

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Message-Id: <e75c8f5a78096a6ee5e63b076cb885fe0e0ea08f.1440407339.git.jslaby@suse.cz>
Date:	Mon, 24 Aug 2015 11:08:50 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
	Adam Radford <linuxraid@....com>,
	Christoph Hellwig <hch@....de>, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 30/82] 3w-xxxx: fix mis-aligned struct accesses

From: Arnd Bergmann <arnd@...db.de>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 4bfaa5c4b99ddec00907e854d70453bd2aef39a0 upstream.

Building an allmodconfig ARM kernel, I get multiple such
warnings because of a spinlock contained in packed structure
in the 3w-xxxx driver:

../drivers/scsi/3w-xxxx.c: In function 'tw_chrdev_ioctl':
../drivers/scsi/3w-xxxx.c:1001:68: warning: mis-aligned access used for structure member [-fstrict-volatile-bitfields]
    timeout = wait_event_timeout(tw_dev->ioctl_wqueue, tw_dev->chrdev_request_id == TW_IOCTL_CHRDEV_FREE, timeout);
                                                                    ^
../drivers/scsi/3w-xxxx.c:1001:68: note: when a volatile object spans multiple type-sized locations, the compiler must choose between using a single mis-aligned access to preserve the volatility, or using multiple aligned accesses to avoid runtime faults; this code may fail at runtime if the hardware does not allow this access

The same bug apparently was present in 3w-sas and 3w-9xxx, but has been
fixed in the past. This patch uses the same fix by moving the pragma
in front of the TW_Device_Extension definition, so it only covers
hardware structures.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
Acked-by: Adam Radford <aradford@...il.com>
Cc: Adam Radford <linuxraid@....com>
Signed-off-by: Christoph Hellwig <hch@....de>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/scsi/3w-xxxx.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/3w-xxxx.h b/drivers/scsi/3w-xxxx.h
index 1d31858766ce..6f65e663d393 100644
--- a/drivers/scsi/3w-xxxx.h
+++ b/drivers/scsi/3w-xxxx.h
@@ -387,6 +387,8 @@ typedef struct TAG_TW_Passthru
 	unsigned char padding[12];
 } TW_Passthru;
 
+#pragma pack()
+
 typedef struct TAG_TW_Device_Extension {
 	u32			base_addr;
 	unsigned long		*alignment_virtual_address[TW_Q_LENGTH];
@@ -425,6 +427,4 @@ typedef struct TAG_TW_Device_Extension {
 	wait_queue_head_t	ioctl_wqueue;
 } TW_Device_Extension;
 
-#pragma pack()
-
 #endif /* _3W_XXXX_H */
-- 
2.5.0

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