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Commit 5ee22bee authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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

Pull randomness bugfix from Ted Ts'o:
 "random: fix entropy accounting bug introduced in v3.15"

* tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random:
  random: fix nasty entropy accounting bug
parents 5cfb277d e33ba5fa

drivers/char/random.c

+9 −8
Original line number Original line Diff line number Diff line
@@ -980,7 +980,6 @@ static void push_to_pool(struct work_struct *work) 
static size_t account(struct entropy_store *r, size_t nbytes, int min,

static size_t account(struct entropy_store *r, size_t nbytes, int min,

		      int reserved)

		      int reserved)

{

{

	int have_bytes;

	int entropy_count, orig;

	int entropy_count, orig;

	size_t ibytes;

	size_t ibytes;
@@ -989,17 +988,19 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min, 
	/* Can we pull enough? */

	/* Can we pull enough? */

retry:

retry:

	entropy_count = orig = ACCESS_ONCE(r->entropy_count);

	entropy_count = orig = ACCESS_ONCE(r->entropy_count);

	have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);

	ibytes = nbytes;

	ibytes = nbytes;

	/* If limited, never pull more than available */

	/* If limited, never pull more than available */

	if (r->limit)

	if (r->limit) {

		ibytes = min_t(size_t, ibytes, have_bytes - reserved);

		int have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);



		if ((have_bytes -= reserved) < 0)

			have_bytes = 0;

		ibytes = min_t(size_t, ibytes, have_bytes);

	}

	if (ibytes < min)

	if (ibytes < min)

		ibytes = 0;

		ibytes = 0;

	if (have_bytes >= ibytes + reserved)

	if ((entropy_count -= ibytes << (ENTROPY_SHIFT + 3)) < 0)

		entropy_count -= ibytes << (ENTROPY_SHIFT + 3);

		entropy_count = 0;

	else

		entropy_count = reserved << (ENTROPY_SHIFT + 3);





	if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)

	if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)

		goto retry;

		goto retry;