Re: [PATCH v4 0/1] Fix buffer over-read in cca_cipher2protkey

[Vasily Gorbik <gor@linux.ibm.com>]

On Wed, Jul 29, 2026 at 01:40:08PM +0200, Harald Freudenberger wrote:
> Add validation of both the actual key buffer size and token length
> fields in all the cca_check_sec*token() functions. Additionally check
> in cca_gencipherkey() for possible underflow with returned key size.
> 
> The CCA token structures contain user-controlled len fields that
> were used in operations without proper validation against both the
> actual buffer size and minimum token structure size. An attacker
> could set this field larger than the actual buffer size, leading to
> reading beyond buffer boundaries. This may result in a kernel crash or
> exposure of memory via sending this as part of a request down to the
> crypto card. Also an attacker could have used a very small len value
> and thus enforce a buffer under-run which may produce similar effects
> as a over-read.
> 
> So now a key must
> - key buf length must be at least sizeof the token struct
> - the key len field inside the token must fit into the range of
>   sizeof key token struct ... key buf length
> 
> Changelog:
> v1 - initial version
> v2 - extend the length check to all cca_check_sec*token() functions,
>      also check for min given buffer length and token length field.
> v3 - there was still a possibility to under-run the length checks in
>      function  cca_gencipherkey(). Fixed as suggested by Ingo.
> v4 - Reviewd-by from Ingo added.
> 
> Harald Freudenberger (1):
>   s390/zcrypt: Fix buffer over-read in cca_cipher2protkey
> 
>  drivers/s390/crypto/pkey_cca.c       | 15 +++----
>  drivers/s390/crypto/zcrypt_ccamisc.c | 64 +++++++++++++++++++++++-----
>  drivers/s390/crypto/zcrypt_ccamisc.h |  6 +--
>  3 files changed, 62 insertions(+), 23 deletions(-)

Applied, thank you!