Patch "HID: core: remove unnecessary WARN_ON() in implement()" has been added to the 4.19-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    HID: core: remove unnecessary WARN_ON() in implement()

to the 4.19-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-core-remove-unnecessary-warn_on-in-implement.patch
and it can be found in the queue-4.19 subdirectory.

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



commit 8bf4d5169a4b92b02e924531636d20390945ff19
Author: Nikita Zhandarovich <n.zhandarovich@xxxxxxxxxx>
Date:   Fri May 17 07:19:14 2024 -0700

    HID: core: remove unnecessary WARN_ON() in implement()
    
    [ Upstream commit 4aa2dcfbad538adf7becd0034a3754e1bd01b2b5 ]
    
    Syzkaller hit a warning [1] in a call to implement() when trying
    to write a value into a field of smaller size in an output report.
    
    Since implement() already has a warn message printed out with the
    help of hid_warn() and value in question gets trimmed with:
            ...
            value &= m;
            ...
    WARN_ON may be considered superfluous. Remove it to suppress future
    syzkaller triggers.
    
    [1]
    WARNING: CPU: 0 PID: 5084 at drivers/hid/hid-core.c:1451 implement drivers/hid/hid-core.c:1451 [inline]
    WARNING: CPU: 0 PID: 5084 at drivers/hid/hid-core.c:1451 hid_output_report+0x548/0x760 drivers/hid/hid-core.c:1863
    Modules linked in:
    CPU: 0 PID: 5084 Comm: syz-executor424 Not tainted 6.9.0-rc7-syzkaller-00183-gcf87f46fd34d #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
    RIP: 0010:implement drivers/hid/hid-core.c:1451 [inline]
    RIP: 0010:hid_output_report+0x548/0x760 drivers/hid/hid-core.c:1863
    ...
    Call Trace:
     <TASK>
     __usbhid_submit_report drivers/hid/usbhid/hid-core.c:591 [inline]
     usbhid_submit_report+0x43d/0x9e0 drivers/hid/usbhid/hid-core.c:636
     hiddev_ioctl+0x138b/0x1f00 drivers/hid/usbhid/hiddev.c:726
     vfs_ioctl fs/ioctl.c:51 [inline]
     __do_sys_ioctl fs/ioctl.c:904 [inline]
     __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:890
     do_syscall_x64 arch/x86/entry/common.c:52 [inline]
     do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
     entry_SYSCALL_64_after_hwframe+0x77/0x7f
    ...
    
    Fixes: 95d1c8951e5b ("HID: simplify implement() a bit")
    Reported-by: <syzbot+5186630949e3c55f0799@xxxxxxxxxxxxxxxxxxxxxxxxx>
    Suggested-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Nikita Zhandarovich <n.zhandarovich@xxxxxxxxxx>
    Signed-off-by: Jiri Kosina <jkosina@xxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index dd1d8d0a46d12..0757097d25507 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -1264,7 +1264,6 @@ static void implement(const struct hid_device *hid, u8 *report,
 			hid_warn(hid,
 				 "%s() called with too large value %d (n: %d)! (%s)\n",
 				 __func__, value, n, current->comm);
-			WARN_ON(1);
 			value &= m;
 		}
 	}