fscrypto: don't use on-stack buffer for key derivation
authorEric Biggers <ebiggers@google.com>
Mon, 14 Nov 2016 01:41:09 +0000 (20:41 -0500)
committerTheodore Ts'o <tytso@mit.edu>
Sun, 20 Nov 2016 01:56:13 +0000 (20:56 -0500)
commit0f0909e242f73c1154272cf04f07fc9afe13e5b8
treeff64e7ce77a05f3cfebe72b2f2706bf5f2101e88
parent3c7018ebf8dbf14e7cd4f5dc648c51fc979f45bb
fscrypto: don't use on-stack buffer for key derivation

With the new (in 4.9) option to use a virtually-mapped stack
(CONFIG_VMAP_STACK), stack buffers cannot be used as input/output for
the scatterlist crypto API because they may not be directly mappable to
struct page.  get_crypt_info() was using a stack buffer to hold the
output from the encryption operation used to derive the per-file key.
Fix it by using a heap buffer.

This bug could most easily be observed in a CONFIG_DEBUG_SG kernel
because this allowed the BUG in sg_set_buf() to be triggered.

Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
fs/crypto/keyinfo.c