The interrupt-status packet reports transmit credits returned by the
device. edge_interrupt_callback() adds the 16-bit value to txCredits
without checking maxTxCredits.

edge_write() uses txCredits minus the software FIFO count as the amount
of data that fits. Since the FIFO is allocated with maxTxCredits bytes,
txCredits exceeding maxTxCredits can cause OOB write in ring buffer.

Cap accumulated credits at maxTxCredits. Conforming devices should never
hit the cap.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Assisted-by: Codex:GPT-5
Signed-off-by: Sunho Park <shpark061104@gmail.com>
---
V2 -> V3: Added missing revision history (no code changes)
V1 -> V2: Replaced min_t() with min() 

v2: https://lore.kernel.org/linux-usb/20260714101316.823942-1-shpark061104@gmail.com/
v1: https://lore.kernel.org/linux-usb/20260714093424.737303-1-shpark061104@gmail.com/
---
 drivers/usb/serial/io_edgeport.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/serial/io_edgeport.c b/drivers/usb/serial/io_edgeport.c
index 34ccf7820537..2ab3f8262259 100644
--- a/drivers/usb/serial/io_edgeport.c
+++ b/drivers/usb/serial/io_edgeport.c
@@ -646,7 +646,9 @@ static void edge_interrupt_callback(struct urb *urb)
 				if (edge_port && edge_port->open) {
 					spin_lock_irqsave(&edge_port->ep_lock,
 							  flags);
-					edge_port->txCredits += txCredits;
+					edge_port->txCredits =
+						min(edge_port->txCredits + txCredits,
+						    edge_port->maxTxCredits);
 					spin_unlock_irqrestore(&edge_port->ep_lock,
 							       flags);
 					dev_dbg(dev, "%s - txcredits for port%d = %d\n",

base-commit: fad0fd120e29041b3e6cdf41bb12e3184fb524a2
-- 
2.43.0

On Tue, Jul 14, 2026 at 07:42:30PM +0900, Sunho Park wrote:
> The interrupt-status packet reports transmit credits returned by the
> device. edge_interrupt_callback() adds the 16-bit value to txCredits
> without checking maxTxCredits.
> 
> edge_write() uses txCredits minus the software FIFO count as the amount
> of data that fits. Since the FIFO is allocated with maxTxCredits bytes,
> txCredits exceeding maxTxCredits can cause OOB write in ring buffer.
> 
> Cap accumulated credits at maxTxCredits. Conforming devices should never
> hit the cap.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Cc: stable@vger.kernel.org
> Assisted-by: Codex:GPT-5
> Signed-off-by: Sunho Park <shpark061104@gmail.com>
> ---
> V2 -> V3: Added missing revision history (no code changes)
> V1 -> V2: Replaced min_t() with min() 
> 
> v2: https://lore.kernel.org/linux-usb/20260714101316.823942-1-shpark061104@gmail.com/
> v1: https://lore.kernel.org/linux-usb/20260714093424.737303-1-shpark061104@gmail.com/

Applied, thanks.

Johan

On Tue, Jul 14, 2026 at 07:42:30PM +0900, Sunho Park wrote:
> The interrupt-status packet reports transmit credits returned by the
> device. edge_interrupt_callback() adds the 16-bit value to txCredits
> without checking maxTxCredits.
> 
> edge_write() uses txCredits minus the software FIFO count as the amount
> of data that fits. Since the FIFO is allocated with maxTxCredits bytes,
> txCredits exceeding maxTxCredits can cause OOB write in ring buffer.
> 
> Cap accumulated credits at maxTxCredits. Conforming devices should never
> hit the cap.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Cc: stable@vger.kernel.org
> Assisted-by: Codex:GPT-5
> Signed-off-by: Sunho Park <shpark061104@gmail.com>
> ---
> V2 -> V3: Added missing revision history (no code changes)
> V1 -> V2: Replaced min_t() with min() 

Please slow down and don't send patches right after each other.  There
might have been other review comments...

On 7/14/26 21:19, Greg Kroah-Hartman wrote:
> Please slow down and don't send patches right after each other.  There
> might have been other review comments...

I apologize for sending patches too quickly. I'm fairly new to the
process, and I'll allow enough time for review in future contributions.

Thanks,
Sunho