Subject: Re: Coverity: iwl_mvm_sec_key_add(): Memory - corruptions

From: Johannes Berg <[email-masked]>
Date: Fri, 18 Nov 2022 22:04:38 +0100

On Fri, 2022-11-18 at 08:54 -0800, coverity-bot wrote:
> 
> *** CID 1527370:  Memory - corruptions  (OVERRUN)
> drivers/net/wireless/intel/iwlwifi/mvm/mld-key.c:123 in iwl_mvm_sec_key_add()
> 117
> 118     	if (WARN_ON(keyconf->keylen > sizeof(cmd.u.add.key)))
> 119     		return -EINVAL;
> 120
> 121     	if (keyconf->cipher == WLAN_CIPHER_SUITE_WEP40 ||
> 122     	    keyconf->cipher == WLAN_CIPHER_SUITE_WEP104)
> vvv     CID 1527370:  Memory - corruptions  (OVERRUN)
> vvv     Overrunning buffer pointed to by "cmd.u.add.key + 3" of 32 bytes by passing it to a function which accesses it at byte offset 34 using argument "keyconf->keylen" (which evaluates to 32). [Note: The source code implementation of the function has been overridden by a builtin model.]
> 123     		memcpy(cmd.u.add.key + IWL_SEC_WEP_KEY_OFFSET, keyconf->key,
> 124     		       keyconf->keylen);
> 125     	else
> 126     		memcpy(cmd.u.add.key, keyconf->key, keyconf->keylen);
> 127
> 128     	if (keyconf->cipher == WLAN_CIPHER_SUITE_TKIP) {
> 
> If this is a false positive, please let us know so we can mark it as
> such, or teach the Coverity rules to be smarter. If not, please make
> sure fixes get into linux-next. :) For patches fixing this, please
> include these lines (but double-check the "Fixes" first):
> 

Well, I don't think you can teach coverity this easily, but the
WARN_ON() check there is not really meant to protect this - WEP keys
must have a length of either 5 or 13 bytes (40 or 104 bits!).

So there's no issue here, but I'm not surprised that coverity wouldn't
be able to figure that out through the stack.

johannes