Patch "HID: hidraw: fix data race on device refcount" has been added to the 6.1-stable tree

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

    HID: hidraw: fix data race on device refcount

to the 6.1-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:
     hid-hidraw-fix-data-race-on-device-refcount.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 944ee77dc6ec7b0afd8ec70ffc418b238c92f12b Mon Sep 17 00:00:00 2001
From: Ludvig Michaelsson <ludvig.michaelsson@xxxxxxxxxx>
Date: Wed, 21 Jun 2023 13:17:43 +0200
Subject: HID: hidraw: fix data race on device refcount

From: Ludvig Michaelsson <ludvig.michaelsson@xxxxxxxxxx>

commit 944ee77dc6ec7b0afd8ec70ffc418b238c92f12b upstream.

The hidraw_open() function increments the hidraw device reference
counter. The counter has no dedicated synchronization mechanism,
resulting in a potential data race when concurrently opening a device.

The race is a regression introduced by commit 8590222e4b02 ("HID:
hidraw: Replace hidraw device table mutex with a rwsem"). While
minors_rwsem is intended to protect the hidraw_table itself, by instead
acquiring the lock for writing, the reference counter is also protected.
This is symmetrical to hidraw_release().

Link: https://github.com/systemd/systemd/issues/27947
Fixes: 8590222e4b02 ("HID: hidraw: Replace hidraw device table mutex with a rwsem")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Ludvig Michaelsson <ludvig.michaelsson@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230621-hidraw-race-v1-1-a58e6ac69bab@xxxxxxxxxx
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/hid/hidraw.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/drivers/hid/hidraw.c
+++ b/drivers/hid/hidraw.c
@@ -272,7 +272,12 @@ static int hidraw_open(struct inode *ino
 		goto out;
 	}
 
-	down_read(&minors_rwsem);
+	/*
+	 * Technically not writing to the hidraw_table but a write lock is
+	 * required to protect the device refcount. This is symmetrical to
+	 * hidraw_release().
+	 */
+	down_write(&minors_rwsem);
 	if (!hidraw_table[minor] || !hidraw_table[minor]->exist) {
 		err = -ENODEV;
 		goto out_unlock;
@@ -301,7 +306,7 @@ static int hidraw_open(struct inode *ino
 	spin_unlock_irqrestore(&hidraw_table[minor]->list_lock, flags);
 	file->private_data = list;
 out_unlock:
-	up_read(&minors_rwsem);
+	up_write(&minors_rwsem);
 out:
 	if (err < 0)
 		kfree(list);


Patches currently in stable-queue which might be from ludvig.michaelsson@xxxxxxxxxx are

queue-6.1/hid-hidraw-fix-data-race-on-device-refcount.patch



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