random: silence compiler warnings and fix race
authorJason A. Donenfeld <Jason@zx2c4.com>
Wed, 14 Jun 2017 22:45:26 +0000 (00:45 +0200)
committerTheodore Ts'o <tytso@mit.edu>
Tue, 20 Jun 2017 01:42:49 +0000 (21:42 -0400)
commit4a072c71f49b0a0e495ea13423bdb850da73c58c
tree6aacee17db1b1619926d0856d7cf74ef22470fdf
parentb169c13de473a85b3c859bb36216a4cb5f00a54a
random: silence compiler warnings and fix race

Odd versions of gcc for the sh4 architecture will actually warn about
flags being used while uninitialized, so we set them to zero. Non crazy
gccs will optimize that out again, so it doesn't make a difference.

Next, over aggressive gccs could inline the expression that defines
use_lock, which could then introduce a race resulting in a lock
imbalance. By using READ_ONCE, we prevent that fate. Finally, we make
that assignment const, so that gcc can still optimize a nice amount.

Finally, we fix a potential deadlock between primary_crng.lock and
batched_entropy_reset_lock, where they could be called in opposite
order. Moving the call to invalidate_batched_entropy to outside the lock
rectifies this issue.

Fixes: b169c13de473a85b3c859bb36216a4cb5f00a54a
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
drivers/char/random.c