On Wed, Sep 27, 2023 at 10:25:03AM +0200, Pablo Neira Ayuso wrote: > On Tue, Sep 26, 2023 at 07:02:19PM -0700, joao@xxxxxxxxxxxxxxxxxx wrote: > > From: Joao Moreira <joao.moreira@xxxxxxxxx> > > > > The function flow_rule_alloc in net/core/flow_offload.c [2] gets an > > unsigned int num_actions (line 10) and later traverses the actions in > > the rule (line 24) setting hw.stats to FLOW_ACTION_HW_STATS_DONT_CARE. > > > > Within the same file, the loop in the line 24 compares a signed int > > (i) to an unsigned int (num_actions), and then uses i as an array > > index. If an integer overflow happens, then the array within the loop > > is wrongly indexed, causing a write out of bounds. > > > > After checking with maintainers, it seems that the front-end caps the > > maximum value of num_action, thus it is not possible to reach the given > > write out of bounds, yet, still, to prevent disasters it is better to > > fix the signedness here. > > > > Similarly, also it is also good to ensure that an overflow won't happen > > in net/netfilter/nf_tables_offload.c's function nft_flow_rule_create by > > making the variable unsigned and ensuring that it returns an error if > > its value reaches UINT_MAX. > > > > This issue was observed by the commit author while reviewing a write-up > > regarding a CVE within the same subsystem [1]. > > I keep spinning around this, this is not really an issue. > > No frontend uses this amount of actions. > > Probably cap this to uint16_t because 2^16 actions is more than > sufficient by now. Actually, even 2^8 actions is more than enough by now.
