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Input: ims-pcu - fix heap-buffer-overflow in ims_pcu_process_data()

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The `ims_pcu_process_data()` processes incoming URB data byte by byte.
However, it fails to check if the `read_pos` index exceeds
IMS_PCU_BUF_SIZE.

If a malicious USB device sends a packet larger than IMS_PCU_BUF_SIZE,
`read_pos` will increment indefinitely. Moreover, since `read_pos` is
located immediately after `read_buf`, the attacker can overwrite
`read_pos` itself to arbitrarily control the index.

This manipulated `read_pos` is subsequently used in
`ims_pcu_handle_response()` to copy data into `cmd_buf`, leading to a
heap buffer overflow.

Specifically, an attacker can overwrite the `cmd_done.wait.head` located
at offset 136 relative to `cmd_buf` in the `ims_pcu_handle_response()`.
Consequently, when the driver calls `complete(&pcu->cmd_done)`, it
triggers a control flow hijack by using the manipulated pointer.

Fix this by adding a bounds check for `read_pos` before writing to
`read_buf`. If the packet is too long, discard it, log a warning,
and reset the parser state.

Fixes: 628329d524 ("Input: add IMS Passenger Control Unit driver")
Co-developed-by: Sanghoon Choi <csh0052@gmail.com>
Signed-off-by: Sanghoon Choi <csh0052@gmail.com>
Signed-off-by: Seungjin Bae <eeodqql09@gmail.com>
Link: https://patch.msgid.link/20251221211442.841549-2-eeodqql09@gmail.com
[dtor: factor out resetting packet state, reset checksum as well]
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
This commit is contained in:
Seungjin Bae 2026-04-08 09:03:59 -07:00 committed by Dmitry Torokhov
parent f7a78e8444
commit 875115b82c
1 changed files with 26 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
drivers/input/misc/ims-pcu.c
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@ -438,6 +438,14 @@ static void ims_pcu_handle_response(struct ims_pcu *pcu)
}
}
static void ims_pcu_reset_packet(struct ims_pcu *pcu)
{
pcu->have_stx = true;
pcu->have_dle = false;
pcu->read_pos = 0;
pcu->check_sum = 0;
}
static void ims_pcu_process_data(struct ims_pcu *pcu, struct urb *urb)
{
int i;
@ -450,6 +458,14 @@ static void ims_pcu_process_data(struct ims_pcu *pcu, struct urb *urb)
continue;
if (pcu->have_dle) {
if (pcu->read_pos >= IMS_PCU_BUF_SIZE) {
dev_warn(pcu->dev,
"Packet too long (%d bytes), discarding\n",
pcu->read_pos);
ims_pcu_reset_packet(pcu);
continue;
}
pcu->have_dle = false;
pcu->read_buf[pcu->read_pos++] = data;
pcu->check_sum += data;
@ -462,10 +478,8 @@ static void ims_pcu_process_data(struct ims_pcu *pcu, struct urb *urb)
dev_warn(pcu->dev,
"Unexpected STX at byte %d, discarding old data\n",
pcu->read_pos);
ims_pcu_reset_packet(pcu);
pcu->have_stx = true;
pcu->have_dle = false;
pcu->read_pos = 0;
pcu->check_sum = 0;
break;
case IMS_PCU_PROTOCOL_DLE:
@ -485,12 +499,18 @@ static void ims_pcu_process_data(struct ims_pcu *pcu, struct urb *urb)
ims_pcu_handle_response(pcu);
}
pcu->have_stx = false;
pcu->have_dle = false;
pcu->read_pos = 0;
ims_pcu_reset_packet(pcu);
break;
default:
if (pcu->read_pos >= IMS_PCU_BUF_SIZE) {
dev_warn(pcu->dev,
"Packet too long (%d bytes), discarding\n",
pcu->read_pos);
ims_pcu_reset_packet(pcu);
continue;
}
pcu->read_buf[pcu->read_pos++] = data;
pcu->check_sum += data;
break;