On Thu, 2025-11-27 at 20:52 +0200, Jarkko Sakkinen wrote: > On Thu, Nov 27, 2025 at 06:17:42PM +0100, Roberto Sassu wrote: > > On Thu, 2025-11-27 at 19:14 +0200, Jarkko Sakkinen wrote: > > > On Thu, Nov 27, 2025 at 05:09:38PM +0100, Roberto Sassu wrote: > > > > On Thu, 2025-11-27 at 15:54 +0200, Jarkko Sakkinen wrote: > > > > > From: Jarkko Sakkinen <[email protected]> > > > > > > > > > > tpm2_get_pcr_allocation() does not cap any upper limit for the number > > > > > of > > > > > banks. Cap the limit to eight banks so that out of bounds values > > > > > coming > > > > > from external I/O cause on only limited harm. > > > > > > > > > > Cc: Roberto Sassu <[email protected]> > > > > > > > > Sorry, I realized that you are expecting me to review. > > > > > > > > I have a couple of questions: > > > > - Could you explain better how out of bounds would occur, since one > > > > could check the number of PCR banks? > > > > - Is dynamic allocation that bad? And if yes, why? > > > > - Couldn't you just check that the number of available PCR banks is > > > > below the threshold you like and keep dynamic allocation? > > > > - Is removing tpm1_get_pcr_allocation() improving code readability? > > > > > > nr_possible_banks is read from external source i.e., neither kernel nor > > > CPU fully control its value. This causes *uncontrolled* dynamic > > > allocation. Thus, it must be capped to some value. > > > > Sure, I'm fine with capping. Isn't that enough? > > It makes sense to make the whole memory allocation then infallible, > especially since it does not have much effect on diff. And it has > not significant effect on memory usage either.
Ok. In that case (even if it does not get in): Reviewed-by: Roberto Sassu <[email protected]> Roberto > But I do see one completely spurious and actually unintended change > that I spotted: tpm1_get_pcr_allocation. It there's no intention > doing this it has just carried over the series. > > I reverted that part, which make it look like a proper bug fix: > > diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c > index 11088bda4e68..6849f216ba0b 100644 > --- a/drivers/char/tpm/tpm1-cmd.c > +++ b/drivers/char/tpm/tpm1-cmd.c > @@ -799,11 +799,6 @@ int tpm1_pm_suspend(struct tpm_chip *chip, u32 > tpm_suspend_pcr) > */ > int tpm1_get_pcr_allocation(struct tpm_chip *chip) > { > - chip->allocated_banks = kcalloc(1, sizeof(*chip->allocated_banks), > - GFP_KERNEL); > - if (!chip->allocated_banks) > - return -ENOMEM; > - > chip->allocated_banks[0].alg_id = TPM_ALG_SHA1; > chip->allocated_banks[0].digest_size = hash_digest_size[HASH_ALGO_SHA1]; > chip->allocated_banks[0].crypto_id = HASH_ALGO_SHA1; > diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c > index 7d77f6fbc152..97501c567c34 100644 > --- a/drivers/char/tpm/tpm2-cmd.c > +++ b/drivers/char/tpm/tpm2-cmd.c > @@ -538,11 +538,9 @@ ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip) > > nr_possible_banks = be32_to_cpup( > (__be32 *)&buf.data[TPM_HEADER_SIZE + 5]); > - > - chip->allocated_banks = kcalloc(nr_possible_banks, > - sizeof(*chip->allocated_banks), > - GFP_KERNEL); > - if (!chip->allocated_banks) { > + if (nr_possible_banks > TPM2_MAX_PCR_BANKS) { > + pr_err("tpm: unexpected number of banks: %u > %u", > + nr_possible_banks, TPM2_MAX_PCR_BANKS); > rc = -ENOMEM; > goto out; > } > diff --git a/include/linux/tpm.h b/include/linux/tpm.h > index dc0338a783f3..eb0ff071bcae 100644 > --- a/include/linux/tpm.h > +++ b/include/linux/tpm.h > @@ -26,7 +26,9 @@ > #include <crypto/aes.h> > > #define TPM_DIGEST_SIZE 20 /* Max TPM v1.2 PCR size */ > -#define TPM_MAX_DIGEST_SIZE SHA512_DIGEST_SIZE > + > +#define TPM2_MAX_DIGEST_SIZE SHA512_DIGEST_SIZE > +#define TPM2_MAX_PCR_BANKS 8 > > struct tpm_chip; > struct trusted_key_payload; > @@ -68,7 +70,7 @@ enum tpm2_curves { > > struct tpm_digest { > u16 alg_id; > - u8 digest[TPM_MAX_DIGEST_SIZE]; > + u8 digest[TPM2_MAX_DIGEST_SIZE]; > } __packed; > > struct tpm_bank_info { > @@ -189,7 +191,7 @@ struct tpm_chip { > unsigned int groups_cnt; > > u32 nr_allocated_banks; > - struct tpm_bank_info *allocated_banks; > + struct tpm_bank_info allocated_banks[TPM2_MAX_PCR_BANKS]; > #ifdef CONFIG_ACPI > acpi_handle acpi_dev_handle; > char ppi_version[TPM_PPI_VERSION_LEN + 1]; > > > > > > Thanks > > > > Roberto > > > > > > Thanks > > > > > > > > Roberto > > > > > > BR, Jarkko > > > > BR, Jarkko
