On Thu, Apr 11, 2019 at 02:32:15PM -0700, Eric Biggers wrote: > From: Eric Biggers <ebiggers@xxxxxxxxxx> > > ->i_crypt_info starts out NULL and may later be locklessly set to a > non-NULL value by the cmpxchg() in fscrypt_get_encryption_info(). > > But ->i_crypt_info is used directly, which technically is incorrect. > It's a data race, and it doesn't include the data dependency barrier > needed to safely dereference the pointer on at least one architecture. > > Fix this by using READ_ONCE() instead. Note: we don't need to use > smp_load_acquire(), since dereferencing the pointer only requires a data > dependency barrier, which is already included in READ_ONCE(). We also > don't need READ_ONCE() in places where ->i_crypt_info is unconditionally > dereferenced, since it must have already been checked. > > Also downgrade the cmpxchg() to cmpxchg_release(), since RELEASE > semantics are sufficient on the write side. > > Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> Looks good, applied. - Ted
