From 9f9bfc80c67f35a275820da7e83a35dface08281 Mon Sep 17 00:00:00 2001 From: Zhang Cen Date: Fri, 22 May 2026 22:54:42 +0800 Subject: [PATCH] USB: serial: cypress_m8: validate interrupt packet headers cypress_read_int_callback() parses the interrupt-in buffer according to the selected Cypress packet format. Format 1 has a two-byte status/count header and format 2 has a one-byte combined status/count header. The usb-serial core sizes the interrupt-in buffer from the endpoint descriptor's wMaxPacketSize, and successful interrupt transfers can complete short when URB_SHORT_NOT_OK is not set. Check that the completed packet contains the selected header before reading it. Malformed short reports are ignored and the interrupt URB is resubmitted through the existing retry path, preventing out-of-bounds header-byte reads. KASAN report as below: KASAN slab-out-of-bounds in cypress_read_int_callback+0x240/0x7f0 Read of size 1 Call trace: cypress_read_int_callback() (drivers/usb/serial/cypress_m8.c:1009) __usb_hcd_giveback_urb() dummy_timer() Fixes: 3416eaa1f8f8 ("USB: cypress_m8: Packet format is separate from characteristic size") Assisted-by: Codex:gpt-5.5 Signed-off-by: Zhang Cen Fixes: 3416eaa1f8f8 ("USB: cypress_m8: Packet format is separate from characteristic size") Cc: stable@vger.kernel.org # 2.6.26 [ johan: use constants in header length sanity checks ] Signed-off-by: Johan Hovold --- drivers/usb/serial/cypress_m8.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/usb/serial/cypress_m8.c b/drivers/usb/serial/cypress_m8.c index 0b8a4e9d7bc5..bcf302e88ca4 100644 --- a/drivers/usb/serial/cypress_m8.c +++ b/drivers/usb/serial/cypress_m8.c @@ -1025,8 +1025,8 @@ static void cypress_read_int_callback(struct urb *urb) char tty_flag = TTY_NORMAL; int bytes = 0; int result; - int i = 0; int status = urb->status; + int i; switch (status) { case 0: /* success */ @@ -1064,22 +1064,32 @@ static void cypress_read_int_callback(struct urb *urb) spin_lock_irqsave(&priv->lock, flags); result = urb->actual_length; + i = 0; switch (priv->pkt_fmt) { default: case packet_format_1: /* This is for the CY7C64013... */ + if (result < 2) + break; priv->current_status = data[0] & 0xF8; bytes = data[1] + 2; i = 2; break; case packet_format_2: /* This is for the CY7C63743... */ + if (result < 1) + break; priv->current_status = data[0] & 0xF8; bytes = (data[0] & 0x07) + 1; i = 1; break; } spin_unlock_irqrestore(&priv->lock, flags); + if (i == 0) { + dev_dbg(dev, "%s - short packet received: %d bytes\n", + __func__, result); + goto continue_read; + } if (result < bytes) { dev_dbg(dev, "%s - wrong packet size - received %d bytes but packet said %d bytes\n",