Merge tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random

Pull /dev/random fix from Ted Ts'o:
 "This fixes a BUG_ON-causing regression that was introduced during the
  last merge window"

* tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random:
  random: fix BUG_ON caused by accounting simplification

1 files changed, 5 insertions, 2 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 6b75713d953a..102c50d38902 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -995,8 +995,11 @@ retry:
                 ibytes = min_t(size_t, ibytes, have_bytes - reserved);
         if (ibytes < min)
                 ibytes = 0;
-        entropy_count = max_t(int, 0,
-                              entropy_count - (ibytes << (ENTROPY_SHIFT + 3)));
+        if (have_bytes >= ibytes + reserved)
+                entropy_count -= ibytes << (ENTROPY_SHIFT + 3);
+        else
+                entropy_count = reserved << (ENTROPY_SHIFT + 3);
+
         if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
                 goto retry;