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

[Harald Freudenberger <freude@linux.ibm.com>]

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(-)

-- 
2.43.0