On Tue, Apr 02, 2019 at 02:46:25AM +0300, Jarkko Sakkinen wrote: > On Mon, Apr 01, 2019 at 12:06:07PM -0700, Kees Cook wrote: > > A "get random" may fail with a TPM error, but those codes were returned > > as-is to the caller, which assumed the result was the number of bytes > > that had been written to the target buffer, which could lead to a kernel > > heap memory exposure and over-read. > > > > This fixes tpm1_get_random() to mask positive TPM errors into -EIO, as > > before. > > > > [ 18.092103] tpm tpm0: A TPM error (379) occurred attempting get random > > [ 18.092106] usercopy: Kernel memory exposure attempt detected from SLUB object 'kmalloc-64' (offset 0, size 379)! > > > > Link: https://bugzilla.redhat.com/show_bug.cgi?id=1650989 > > Reported-by: Phil Baker <baker1tex@xxxxxxxxx> > > Reported-by: Craig Robson <craig@xxxxxxxxx> > > Fixes: 7aee9c52d7ac ("tpm: tpm1: rewrite tpm1_get_random() using tpm_buf structure") > > Cc: Laura Abbott <labbott@xxxxxxxxxx> > > Cc: Tomas Winkler <tomas.winkler@xxxxxxxxx> > > Cc: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> > > Cc: stable@xxxxxxxxxxxxxxx > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > > --- > > v3: fix never-succeed, limit checks to tpm cmd return (James, Jason) > > v2: also fix tpm2 implementation (Jason Gunthorpe) > > --- > > drivers/char/tpm/tpm1-cmd.c | 7 +++++-- > > drivers/char/tpm/tpm2-cmd.c | 7 +++++-- > > 2 files changed, 10 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c > > index 85dcf2654d11..faacbe1ffa1a 100644 > > --- a/drivers/char/tpm/tpm1-cmd.c > > +++ b/drivers/char/tpm/tpm1-cmd.c > > @@ -510,7 +510,7 @@ struct tpm1_get_random_out { > > * > > * Return: > > * * number of bytes read > > - * * -errno or a TPM return code otherwise > > + * * -errno (positive TPM return codes are masked to -EIO) > > */ > > int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max) > > { > > @@ -531,8 +531,11 @@ int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max) > > > > rc = tpm_transmit_cmd(chip, &buf, sizeof(out->rng_data_len), > > "attempting get random"); > > - if (rc) > > + if (rc) { > > + if (rc > 0) > > + rc = -EIO; > > goto out; > > + } > > > > out = (struct tpm1_get_random_out *)&buf.data[TPM_HEADER_SIZE]; > > > > diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c > > index e74c5b7b64bf..8ffa6af61580 100644 > > --- a/drivers/char/tpm/tpm2-cmd.c > > +++ b/drivers/char/tpm/tpm2-cmd.c > > @@ -301,7 +301,7 @@ struct tpm2_get_random_out { > > * > > * Return: > > * size of the buffer on success, > > - * -errno otherwise > > + * -errno otherwise ((positive TPM return codes are masked to -EIO) > > */ > > int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max) > > { > > @@ -328,8 +328,11 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max) > > offsetof(struct tpm2_get_random_out, > > buffer), > > "attempting get random"); > > - if (err) > > + if (err) { > > + if (err > 0) > > + err = -EIO; > > goto out; > > + } > > > > out = (struct tpm2_get_random_out *) > > &buf.data[TPM_HEADER_SIZE]; > > -- > > 2.17.1 > > > > > > -- > > Kees Cook > > Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> Applied to my master branch. Jason, Tomas, do you want me to add reviewed-by's? /Jarkko
