From: Jinmo Yang Date: Thu, 28 May 2026 17:59:45 +0000 (+0900) Subject: HID: wacom: fix slab-out-of-bounds write in wacom_wac_queue_insert X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=6b3014ec0e9a390ca563030b2d7689921f0daef5;p=thirdparty%2Fkernel%2Flinux.git HID: wacom: fix slab-out-of-bounds write in wacom_wac_queue_insert wacom_wac_queue_insert() calls kfifo_skip() in a loop when the kfifo doesn't have enough space for the incoming report. If the kfifo is empty, kfifo_skip() reads stale data left in the kmalloc'd buffer via __kfifo_peek_n() and interprets it as a record length, advancing fifo->out by that garbage value. This corrupts the internal kfifo state, causing kfifo_unused() to return a value much larger than the actual buffer size, which bypasses __kfifo_in_r()'s guard: if (len + recsize > kfifo_unused(fifo)) return 0; kfifo_copy_in() then performs an out-of-bounds memcpy, writing up to 3842 bytes past the 256-byte buffer. Add a !kfifo_is_empty() condition to the while loop so kfifo_skip() is never called on an empty fifo, and check the return value of kfifo_in() to reject reports that are too large for the fifo. Suggested-by: Dmitry Torokhov Fixes: 5e013ad20689 ("HID: wacom: Remove static WACOM_PKGLEN_MAX limit") Cc: stable@vger.kernel.org Signed-off-by: Jinmo Yang Reviewed-by: Dmitry Torokhov Signed-off-by: Benjamin Tissoires --- diff --git a/drivers/hid/wacom_sys.c b/drivers/hid/wacom_sys.c index 2220168bf1164..fac75c2024539 100644 --- a/drivers/hid/wacom_sys.c +++ b/drivers/hid/wacom_sys.c @@ -54,7 +54,7 @@ static void wacom_wac_queue_insert(struct hid_device *hdev, { bool warned = false; - while (kfifo_avail(fifo) < size) { + while (kfifo_avail(fifo) < size && !kfifo_is_empty(fifo)) { if (!warned) hid_warn(hdev, "%s: kfifo has filled, starting to drop events\n", __func__); warned = true; @@ -62,7 +62,9 @@ static void wacom_wac_queue_insert(struct hid_device *hdev, kfifo_skip(fifo); } - kfifo_in(fifo, raw_data, size); + if (!kfifo_in(fifo, raw_data, size)) + hid_warn_ratelimited(hdev, "%s: report is too large (%d)\n", + __func__, size); } static void wacom_wac_queue_flush(struct hid_device *hdev,