spi: ch341: fix out-of-bounds memory access in ch341_transfer_one

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: spi: ch341: fix out-of-bounds memory access in ch341_transfer_one Discovered by Atuin - Automated Vulnerability Discovery Engine. The 'len' variable is calculated as 'min(32, trans->len + 1)', which includes the 1-byte command header. When copying data from 'trans->tx_buf' to 'ch341->tx_buf + 1', using 'len' as the length is incorrect because: 1. It causes an out-of-bounds read from 'trans->tx_buf' (which has size 'trans->len', i.e., 'len - 1' in this context). 2. It can cause an out-of-bounds write to 'ch341->tx_buf' if 'len' is CH341_PACKET_LENGTH (32). Writing 32 bytes to ch341->tx_buf + 1 overflows the buffer. Fix this by copying 'len - 1' bytes.

References

• https://git.kernel.org/stable/c/cad6c0fd6f3c0e76a1f75df4bce3b08a13f08974
• https://git.kernel.org/stable/c/ea1e43966cd03098fcd5f0d72e6c2901d45fa08d
• https://git.kernel.org/stable/c/81841da1f30f66a850cc8796d99ba330aad9d696
• https://git.kernel.org/stable/c/545d1287e40a55242f6ab68bcc1ba3b74088b1bc