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

a26fb01c · Linus Torvalds <[email protected]> · 2018-07-28 19:40:06 -07:00

Pull random fixes from Ted Ts'o:
 "In reaction to the fixes to address CVE-2018-1108, some Linux
  distributions that have certain systemd versions in some cases
  combined with patches to libcrypt for FIPS/FEDRAMP compliance, have
  led to boot-time stalls for some hardware.

  The reaction by some distros and Linux sysadmins has been to install
  packages that try to do complicated things with the CPU and hope that
  leads to randomness.

  To mitigate this, if RDRAND is available, mix it into entropy provided
  by userspace. It won't hurt, and it will probably help"

* tag 'random_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random:
  random: mix rdrand with entropy sent in from userspace

Commit: a26fb01c2879ed7026e6cbd78bb701912d249eef
Parents: 2ffb57df · 81e69df3

Merge commit. Changes below are compared with the first parent: 2ffb57df.

Changes

1 files changed · +9 −1

File	Status	Add	Del	Content
drivers/char/random.c	modified	+9	−1	View file

drivers/char/random.c

View file

diff --git a/drivers/char/random.c b/drivers/char/random.c
index cd888d4..bd449ad 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1895,14 +1895,22 @@ static int
 write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
 {
 	size_t bytes;
-	__u32 buf[16];
+	__u32 t, buf[16];
 	const char __user *p = buffer;
 
 	while (count > 0) {
+		int b, i = 0;
+
 		bytes = min(count, sizeof(buf));
 		if (copy_from_user(&buf, p, bytes))
 			return -EFAULT;
 
+		for (b = bytes ; b > 0 ; b -= sizeof(__u32), i++) {
+			if (!arch_get_random_int(&t))
+				break;
+			buf[i] ^= t;
+		}
+
 		count -= bytes;
 		p += bytes;
 