modbus: Fix buffer overrun in RTU RX handler #100548
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It's possible for uart_buf_ctr to decrement after checking it due to TX interrupts. This can cause the unsigned packet length to overflow when subtracted by 4, which makes memcpy and crc16_ansi overflow the UART buffer. The counter is just loaded into a local variable to prevent further modification. Partially fixes zephyrproject-rtos#91088 Signed-off-by: Abram Early <[email protected]>
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It's possible for uart_buf_ctr to decrement after checking it due to TX interrupts. This can cause the unsigned packet length to overflow when subtracted by 4, which makes memcpy and crc16_ansi overflow the UART buffer. The counter is just loaded into a local variable to prevent further modification.
Partially fixes #91088