James Bottomley @ 2020-07-21 17:39 MST: > On Tue, 2020-07-21 at 17:02 -0700, Jerry Snitselaar wrote: >> James Bottomley @ 2020-07-21 16:37 MST: >> >> > On Tue, 2020-07-21 at 16:16 -0700, Jerry Snitselaar wrote: >> > > James Bottomley @ 2020-07-21 08:56 MST: >> > >> > [...] >> > > > + /* >> > > > + * This will only trigger if someone has added an >> > > > additional >> > > > + * hash to the tpm_algorithms enum without >> > > > incrementing >> > > > + * TPM_MAX_HASHES. This has to be a BUG_ON because >> > > > under >> > > > this >> > > > + * condition, the chip->groups array will overflow >> > > > corrupting >> > > > + * the chips structure. >> > > > + */ >> > > > + BUG_ON(chip->groups_cnt > TPM_MAX_HASHES); >> > > >> > > Should this check be 3 + TPM_MAX_HASHES like below? >> > >> > No, because at this point only a single additional group has been >> > addedin addition to the hashes groups. The first line of >> > tpm_sysfs_add_device is >> > >> > WARN_ON(chip->groups_cnt != 0); >> > >> > And then we add the unnamed group. This loop over the banks >> > follows it, so chip->groups_cnt should be nr_banks_allocated by the >> > end (it's the index, which is one fewer than the number of entries >> > in chip->groups[]). We have a problem if nr_banks_allocated > >> > TPM_MAX_HASHES >> > >> > which is what the BUG_ON checks. >> > >> > James >> >> If the chip supported all 5 listed cases wouldn't groups_cnt be 6 at >> this point? > > Actually, yes, I think it would be because it's pointing at the next > free index not the current one. So it should be BUG_ON (chip- >>groups_cnt > TPM_MAX_HASHES + 1) > > James One other thought, should a note be added above tpm_algorithms to note that when that is changed TPM_MAX_HASHES should be changed as well? With the above change to the BUG_ON you can add to v3: Reviewed-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>
