From 69c02ffde6ed4d535fa4e693a9e572729cad3d0d Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Mon, 6 Apr 2026 16:04:10 +0200 Subject: [PATCH] HID: core: clamp report_size in s32ton() to avoid undefined shift s32ton() shifts by n-1 where n is the field's report_size, a value that comes directly from a HID device. The HID parser bounds report_size only to <= 256, so a broken HID device can supply a report descriptor with a wide field that triggers shift exponents up to 256 on a 32-bit type when an output report is built via hid_output_field() or hid_set_field(). Commit ec61b41918587 ("HID: core: fix shift-out-of-bounds in hid_report_raw_event") added the same n > 32 clamp to the function snto32(), but s32ton() was never given the same fix as I guess syzbot hadn't figured out how to fuzz a device the same way. Fix this up by just clamping the max value of n, just like snto32() does. Cc: stable Cc: Jiri Kosina Cc: Benjamin Tissoires Cc: linux-input@vger.kernel.org Assisted-by: gregkh_clanker_t1000 Signed-off-by: Greg Kroah-Hartman Signed-off-by: Jiri Kosina --- drivers/hid/hid-core.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c index 61bc42c44909..dd78884a200a 100644 --- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -71,6 +71,9 @@ static u32 s32ton(__s32 value, unsigned int n) if (!value || !n) return 0; + if (n > 32) + n = 32; + a = value >> (n - 1); if (a && a != -1) return value < 0 ? 1 << (n - 1) : (1 << (n - 1)) - 1;