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

From: Tianchu Chen <[email protected]>

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.

---
 drivers/spi/spi-ch341.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 46bc208f2..79d2f9ab4 100644
@@ -78,7 +78,7 @@ static int ch341_transfer_one(struct spi_controller *host,
 
 	ch341->tx_buf[0] = CH341A_CMD_SPI_STREAM;
 
-	memcpy(ch341->tx_buf + 1, trans->tx_buf, len);
+	memcpy(ch341->tx_buf + 1, trans->tx_buf, len - 1);
 
 	ret = usb_bulk_msg(ch341->udev, ch341->write_pipe, ch341->tx_buf, len,
 			   NULL, CH341_DEFAULT_TIMEOUT);

2.39.5

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman. You have sent him a patch that has triggered this response. He used to manually respond to these common problems, but in order to save his sanity (he kept writing the same thing over and over, yet to different people), I was created. Hopefully you will not take offence and will fix the problem in your patch and resubmit it so that it can be accepted into the Linux kernel tree.

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Applied to

https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next

Thanks!

[1/1] spi: ch341: fix out-of-bounds memory access in ch341_transfer_one

      commit: 545d1287e40a55242f6ab68bcc1ba3b74088b1bc

All being well this means that it will be integrated into the linux-next tree (usually sometime in the next 24 hours) and sent to Linus during the next merge window (or sooner if it is a bug fix), however if problems are discovered then the patch may be dropped or reverted.

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Thanks,
Mark