can: j1939: j1939_tp_tx_dat_new(): fix out-of-bounds memory access

In the j1939_tp_tx_dat_new() function, an out-of-bounds memory access
could occur during the memcpy() operation if the size of skb->cb is
larger than the size of struct j1939_sk_buff_cb. This is because the
memcpy() operation uses the size of skb->cb, leading to a read beyond
the struct j1939_sk_buff_cb.

Updated the memcpy() operation to use the size of struct
j1939_sk_buff_cb instead of the size of skb->cb. This ensures that the
memcpy() operation only reads the memory within the bounds of struct
j1939_sk_buff_cb, preventing out-of-bounds memory access.

Additionally, add a BUILD_BUG_ON() to check that the size of skb->cb
is greater than or equal to the size of struct j1939_sk_buff_cb. This
ensures that the skb->cb buffer is large enough to hold the
j1939_sk_buff_cb structure.

Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
Reported-by: Shuangpeng Bai <[email protected]>
Tested-by: Shuangpeng Bai <[email protected]>
Signed-off-by: Oleksij Rempel <[email protected]>
Link: https://groups.google.com/g/syzkaller/c/G_LL-C3plRs/m/-8xCi6dCAgAJ
Link: https://lore.kernel.org/all/[email protected]
Cc: [email protected]
[mkl: rephrase commit message]
Signed-off-by: Marc Kleine-Budde <[email protected]>

0 files changed, 0 insertions, 0 deletions