The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x a6b87bfc2ab5bccb7ad953693c85d9062aef3fdd # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025081232-clear-humility-0629@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a6b87bfc2ab5bccb7ad953693c85d9062aef3fdd Mon Sep 17 00:00:00 2001 From: Alan Stern stern@rowland.harvard.edu Date: Wed, 23 Jul 2025 10:37:04 -0400 Subject: [PATCH] HID: core: Harden s32ton() against conversion to 0 bits

Testing by the syzbot fuzzer showed that the HID core gets a shift-out-of-bounds exception when it tries to convert a 32-bit quantity to a 0-bit quantity. Ideally this should never occur, but there are buggy devices and some might have a report field with size set to zero; we shouldn't reject the report or the device just because of that.

Instead, harden the s32ton() routine so that it returns a reasonable result instead of crashing when it is called with the number of bits set to 0 -- the same as what snto32() does.

Signed-off-by: Alan Stern stern@rowland.harvard.edu Reported-by: syzbot+b63d677d63bcac06cf90@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-usb/68753a08.050a0220.33d347.0008.GAE@google.c... Tested-by: syzbot+b63d677d63bcac06cf90@syzkaller.appspotmail.com Fixes: dde5845a529f ("[PATCH] Generic HID layer - code split") Cc: stable@vger.kernel.org Link: https://patch.msgid.link/613a66cd-4309-4bce-a4f7-2905f9bce0c9@rowland.harvar... Signed-off-by: Benjamin Tissoires bentiss@kernel.org

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c index ef1f79951d9b..f7d4efcae603 100644 --- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -66,8 +66,12 @@ static s32 snto32(__u32 value, unsigned int n)

static u32 s32ton(__s32 value, unsigned int n) { - s32 a = value >> (n - 1); + s32 a;

+ if (!value || !n) + return 0; + + a = value >> (n - 1); if (a && a != -1) return value < 0 ? 1 << (n - 1) : (1 << (n - 1)) - 1; return value & ((1 << n) - 1);