Patch "bna: avoid writing uninitialized data into hw registers" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

bna: avoid writing uninitialized data into hw registers

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
bna-avoid-writing-uninitialized-data-into-hw-registers.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Arnd Bergmann <[email protected]>
Date: Thu, 23 Mar 2017 17:07:26 +0100
Subject: bna: avoid writing uninitialized data into hw registers

From: Arnd Bergmann <[email protected]>

[ Upstream commit a5af83925363eb85d467933e3d6ec5a87001eb7c ]

The latest gcc-7 snapshot warns about bfa_ioc_send_enable/bfa_ioc_send_disable writing undefined values into the hardware registers:

drivers/net/ethernet/brocade/bna/bfa_ioc.c: In function 'bfa_iocpf_sm_disabling_entry':
arch/arm/include/asm/io.h:109:22: error: '*((void *)&disable_req+4)' is used uninitialized in this function [-Werror=uninitialized] arch/arm/include/asm/io.h:109:22: error: '*((void *)&disable_req+8)' is used uninitialized in this function [-Werror=uninitialized]

The two functions look like they should do the same thing, but only one of them initializes the time stamp and clscode field. The fact that we only get a warning for one of the two functions seems to be arbitrary, based on the inlining decisions in the compiler.

To address this, I'm making both functions do the same thing:

- set the clscode from the ioc structure in both
- set the time stamp from ktime_get_real_seconds (which also avoids the signed-integer overflow in 2038 and extends the well-defined behavior until 2106).
- zero-fill the reserved field

---
 drivers/net/ethernet/brocade/bna/bfa_ioc.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

@@ -1930,13 +1930,13 @@ static void
 bfa_ioc_send_enable(struct bfa_ioc *ioc)
 {
 	struct bfi_ioc_ctrl_req enable_req;
-	struct timeval tv;
 
 	bfi_h2i_set(enable_req.mh, BFI_MC_IOC, BFI_IOC_H2I_ENABLE_REQ,
 		    bfa_ioc_portid(ioc));
 	enable_req.clscode = htons(ioc->clscode);
-	do_gettimeofday(&tv);
-	enable_req.tv_sec = ntohl(tv.tv_sec);
+	enable_req.rsvd = htons(0);
+	/* overflow in 2106 */
+	enable_req.tv_sec = ntohl(ktime_get_real_seconds());
 	bfa_ioc_mbox_send(ioc, &enable_req, sizeof(struct bfi_ioc_ctrl_req));
 }
 

@@ -1947,6 +1947,10 @@ bfa_ioc_send_disable(struct bfa_ioc *ioc
 
 	bfi_h2i_set(disable_req.mh, BFI_MC_IOC, BFI_IOC_H2I_DISABLE_REQ,
 		    bfa_ioc_portid(ioc));
+	disable_req.clscode = htons(ioc->clscode);
+	disable_req.rsvd = htons(0);
+	/* overflow in 2106 */
+	disable_req.tv_sec = ntohl(ktime_get_real_seconds());
 	bfa_ioc_mbox_send(ioc, &disable_req, sizeof(struct bfi_ioc_ctrl_req));
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/hwmon-asus_atk0110-fix-uninitialized-data-access.patch queue-4.9/bna-avoid-writing-uninitialized-data-into-hw-registers.patch queue-4.9/virtio-balloon-use-actual-number-of-stats-for-stats-queue-buffers.patch queue-4.9/virtio_balloon-prevent-uninitialized-variable-use.patch queue-4.9/isdn-kcapi-avoid-uninitialized-data.patch