Re: [PATCH] hid: fix I2C read buffer overflow in raw_event() for mcp2221
From: Arnaud Lecomte <hidden>
Date: 2025-08-05 21:07:44
Also in:
linux-i2c, lkml
Hi Benjamin, I’m forwarding this patch to you since I noticed that Rishi’s last activity on the Linux mailing list was over three years ago, he may no longer be actively involved. Please let me know if this is the right approach or if there’s a more appropriate way to proceed. I’d hate to cause any inconvenience. Cheers, Arnaud On 26/07/2025 23:09, Arnaud Lecomte wrote:
quoted hunk ↗ jump to hunk
As reported by syzbot, mcp2221_raw_event lacked validation of incoming I2C read data sizes, risking buffer overflows in mcp->rxbuf during multi-part transfers. As highlighted in the DS20005565B spec, p44, we have: "The number of read-back data bytes to follow in this packet: from 0 to a maximum of 60 bytes of read-back bytes." This patch enforces we don't exceed this limit. Reported-by: syzbot+52c1a7d3e5b361ccd346@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=52c1a7d3e5b361ccd346 Tested-by: syzbot+52c1a7d3e5b361ccd346@syzkaller.appspotmail.com Signed-off-by: Arnaud Lecomte <redacted> --- drivers/hid/hid-mcp2221.c | 4 ++++ 1 file changed, 4 insertions(+)diff --git a/drivers/hid/hid-mcp2221.c b/drivers/hid/hid-mcp2221.c index 0f93c22a479f..83941b916cd6 100644 --- a/drivers/hid/hid-mcp2221.c +++ b/drivers/hid/hid-mcp2221.c@@ -814,6 +814,10 @@ static int mcp2221_raw_event(struct hid_device *hdev, } if (data[2] == MCP2221_I2C_READ_COMPL || data[2] == MCP2221_I2C_READ_PARTIAL) { + if (!mcp->rxbuf || mcp->rxbuf_idx < 0 || data[3] > 60) { + mcp->status = -EINVAL; + break; + } buf = mcp->rxbuf; memcpy(&buf[mcp->rxbuf_idx], &data[4], data[3]); mcp->rxbuf_idx = mcp->rxbuf_idx + data[3];