Commit
d4c08afafa04 ("s390/qeth: streamline SNMP cmd code") removed
the bounds checking for req_len, under the assumption that the check in
qeth_alloc_cmd() would suffice.
But that code path isn't sufficiently robust to handle a user-provided
data_length, which could overflow (when adding the cmd header overhead)
before being checked against QETH_BUFSIZE. We end up allocating just a
tiny iob, and the subsequent copy_from_user() writes past the end of
that iob.
Special-case this path and add a coarse bounds check, to protect against
maliciuous requests. This let's the subsequent code flow do its normal
job and precise checking, without risk of overflow.
Fixes: d4c08afafa04 ("s390/qeth: streamline SNMP cmd code")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
get_user(req_len, &ureq->hdr.req_len))
return -EFAULT;
+ /* Sanitize user input, to avoid overflows in iob size calculation: */
+ if (req_len > QETH_BUFSIZE)
+ return -EINVAL;
+
iob = qeth_get_adapter_cmd(card, IPA_SETADP_SET_SNMP_CONTROL, req_len);
if (!iob)
return -ENOMEM;