diff options
| author | Ali Norouzi <ali.norouzi@keysight.com> | 2026-03-19 16:47:44 +0100 |
|---|---|---|
| committer | Marc Kleine-Budde <mkl@pengutronix.de> | 2026-03-19 17:16:02 +0100 |
| commit | b9c310d72783cc2f30d103eed83920a5a29c671a (patch) | |
| tree | 66505eff7be9f58dfa56aa6c7f56a631d1052803 | |
| parent | 46eee1661aa9b49966e6c43d07126fe408edda57 (diff) | |
can: gw: fix OOB heap access in cgw_csum_crc8_rel()
cgw_csum_crc8_rel() correctly computes bounds-safe indices via calc_idx():
int from = calc_idx(crc8->from_idx, cf->len);
int to = calc_idx(crc8->to_idx, cf->len);
int res = calc_idx(crc8->result_idx, cf->len);
if (from < 0 || to < 0 || res < 0)
return;
However, the loop and the result write then use the raw s8 fields directly
instead of the computed variables:
for (i = crc8->from_idx; ...) /* BUG: raw negative index */
cf->data[crc8->result_idx] = ...; /* BUG: raw negative index */
With from_idx = to_idx = result_idx = -64 on a 64-byte CAN FD frame,
calc_idx(-64, 64) = 0 so the guard passes, but the loop iterates with
i = -64, reading cf->data[-64], and the write goes to cf->data[-64].
This write might end up to 56 (7.0-rc) or 40 (<= 6.19) bytes before the
start of the canfd_frame on the heap.
The companion function cgw_csum_xor_rel() uses `from`/`to`/`res`
correctly throughout; fix cgw_csum_crc8_rel() to match.
Confirmed with KASAN on linux-7.0-rc2:
BUG: KASAN: slab-out-of-bounds in cgw_csum_crc8_rel+0x515/0x5b0
Read of size 1 at addr ffff8880076619c8 by task poc_cgw_oob/62
To configure the can-gw crc8 checksums CAP_NET_ADMIN is needed.
Fixes: 456a8a646b25 ("can: gw: add support for CAN FD frames")
Cc: stable@vger.kernel.org
Reported-by: Ali Norouzi <ali.norouzi@keysight.com>
Reviewed-by: Oliver Hartkopp <socketcan@hartkopp.net>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Ali Norouzi <ali.norouzi@keysight.com>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20260319-fix-can-gw-and-can-isotp-v2-1-c45d52c6d2d8@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
| -rw-r--r-- | net/can/gw.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/net/can/gw.c b/net/can/gw.c index 8ee4d67a07d3..0ec99f68aa45 100644 --- a/net/can/gw.c +++ b/net/can/gw.c @@ -375,10 +375,10 @@ static void cgw_csum_crc8_rel(struct canfd_frame *cf, return; if (from <= to) { - for (i = crc8->from_idx; i <= crc8->to_idx; i++) + for (i = from; i <= to; i++) crc = crc8->crctab[crc ^ cf->data[i]]; } else { - for (i = crc8->from_idx; i >= crc8->to_idx; i--) + for (i = from; i >= to; i--) crc = crc8->crctab[crc ^ cf->data[i]]; } @@ -397,7 +397,7 @@ static void cgw_csum_crc8_rel(struct canfd_frame *cf, break; } - cf->data[crc8->result_idx] = crc ^ crc8->final_xor_val; + cf->data[res] = crc ^ crc8->final_xor_val; } static void cgw_csum_crc8_pos(struct canfd_frame *cf, |