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HID: mcp2221: clear rxbuf after I2C/SMBus transfer completes

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mcp_i2c_smbus_read() stores the caller-supplied buffer pointer in
mcp->rxbuf for the duration of a transfer but never clears it when the
transfer finishes or times out. Once the caller frees or reuses the
buffer, mcp->rxbuf becomes a dangling pointer. A delayed or spurious
MCP2221_I2C_GET_DATA report can then drive mcp2221_raw_event() to
memcpy device data into the freed memory, causing a write
use-after-free.

Route all return paths through a single exit point that clears
mcp->rxbuf and mcp->rxbuf_size, so that the existing !mcp->rxbuf guard
in the raw_event handler can reject any report arriving after the
transfer has ended.

Fixes: 67a95c2146 ("HID: mcp2221: add usb to i2c-smbus host bridge")
Cc: stable@vger.kernel.org
Signed-off-by: Jiangshan Yi <yijiangshan@kylinos.cn>
Signed-off-by: Jiri Kosina <jkosina@suse.com>
This commit is contained in:
Jiangshan Yi 2026-07-28 21:14:41 +08:00 committed by Jiri Kosina
parent dca151633c
commit db2333f887
1 changed files with 6 additions and 2 deletions
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8
drivers/hid/hid-mcp2221.c
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@ -343,7 +343,7 @@ static int mcp_i2c_smbus_read(struct mcp2221 *mcp,
ret = mcp_send_data_req_status(mcp, mcp->txbuf, 4);
if (ret)
return ret;
goto out;
mcp->rxbuf_idx = 0;
@ -365,7 +365,7 @@ static int mcp_i2c_smbus_read(struct mcp2221 *mcp,
} else {
usleep_range(980, 1000);
mcp_cancel_last_cmd(mcp);
return ret;
goto out;
}
} else {
retries = 0;
@ -375,6 +375,10 @@ static int mcp_i2c_smbus_read(struct mcp2221 *mcp,
usleep_range(980, 1000);
ret = mcp_chk_last_cmd_status_free_bus(mcp);
out:
mcp->rxbuf = NULL;
mcp->rxbuf_size = 0;
return ret;
}