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patch "mei: avoid iterator usage outside of list_for_each_entry" added to char-misc-next

PATCH [email protected] 1 participant 1 message Mar 19, 2022

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Stable branch Char and misc drivers Intel management engine (mei)
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This is a note to let you know that I've just added the patch titled

mei: avoid iterator usage outside of list_for_each_entry

to my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-next branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release during the merge window.

If you have any questions about this process, please let me know.

From c10187b1c5ebb8681ca467ab7b0ded5ea415d258 Mon Sep 17 00:00:00 2001
From: Alexander Usyskin <[email protected]>
Date: Tue, 8 Mar 2022 11:59:26 +0200
Subject: mei: avoid iterator usage outside of list_for_each_entry

Usage of the iterator outside of the list_for_each_entry is considered harmful. https://lkml.org/lkml/2022/2/17/1032

Do not reference the loop variable outside of the loop, by rearranging the orders of execution.
Instead of performing search loop and checking outside the loop if the end of the list was hit and no matching element was found, the execution is performed inside the loop upon a successful match followed by a goto statement to the next step,
therefore no condition has to be performed after the loop has ended.

Cc <[email protected]>
Signed-off-by Alexander Usyskin <[email protected]>
Signed-off-by Tomas Winkler <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/misc/mei/interrupt.c | 35 +++++++++++++++--------------------
 1 file changed, 15 insertions(+), 20 deletions(-)
drivers/misc/mei/interrupt.c +15 -20
index a67f4f2d33a9..0706322154cb 100644
@@ -424,31 +424,26 @@ int mei_irq_read_handler(struct mei_device *dev,
 	list_for_each_entry(cl, &dev->file_list, link) {
 		if (mei_cl_hbm_equal(cl, mei_hdr)) {
 			cl_dbg(dev, cl, "got a message\n");
-			break;
+			ret = mei_cl_irq_read_msg(cl, mei_hdr, meta_hdr, cmpl_list);
+			goto reset_slots;
 		}
 	}
 
 	/* if no recipient cl was found we assume corrupted header */
-	if (&cl->link == &dev->file_list) {
-		/* A message for not connected fixed address clients
-		 * should be silently discarded
-		 * On power down client may be force cleaned,
-		 * silently discard such messages
-		 */
-		if (hdr_is_fixed(mei_hdr) ||
-		    dev->dev_state == MEI_DEV_POWER_DOWN) {
-			mei_irq_discard_msg(dev, mei_hdr, mei_hdr->length);
-			ret = 0;
-			goto reset_slots;
-		}
-		dev_err(dev->dev, "no destination client found 0x%08X\n",
-				dev->rd_msg_hdr[0]);
-		ret = -EBADMSG;
-		goto end;
+	/* A message for not connected fixed address clients
+	 * should be silently discarded
+	 * On power down client may be force cleaned,
+	 * silently discard such messages
+	 */
+	if (hdr_is_fixed(mei_hdr) ||
+	    dev->dev_state == MEI_DEV_POWER_DOWN) {
+		mei_irq_discard_msg(dev, mei_hdr, mei_hdr->length);
+		ret = 0;
+		goto reset_slots;
 	}
-
-	ret = mei_cl_irq_read_msg(cl, mei_hdr, meta_hdr, cmpl_list);
-
+	dev_err(dev->dev, "no destination client found 0x%08X\n", dev->rd_msg_hdr[0]);
+	ret = -EBADMSG;
+	goto end;
 
 reset_slots:
 	/* reset the number of slots and header */
Signature · 1 line
2.35.1