1 files changed, 54 insertions, 0 deletions
diff --git a/debian/patches/random-util-eat-up-bad-RDRAND-values-seen-on-AMD-CPUs.patch b/debian/patches/random-util-eat-up-bad-RDRAND-values-seen-on-AMD-CPUs.patch
new file mode 100644
index 0000000..5c464ad
--- /dev/null
+++ b/debian/patches/random-util-eat-up-bad-RDRAND-values-seen-on-AMD-CPUs.patch
@@ -0,0 +1,54 @@
+From: Michael Biebl <biebl@debian.org>
+Date: Tue, 14 May 2019 13:12:35 +0200
+Subject: random-util: eat up bad RDRAND values seen on AMD CPUs
+
+An ugly, ugly work-around for #11810. And no, we shouldn't have to do
+this. This is something for AMD, the firmware or the kernel to
+fix/work-around, not us. But nonetheless, this should do it for now.
+
+Fixes: #11810
+(cherry picked from commit 1c53d4a070edbec8ad2d384ba0014d0eb6bae077)
+---
+ src/basic/random-util.c | 15 ++++++++++++++-
+ 1 file changed, 14 insertions(+), 1 deletion(-)
+
+diff --git a/src/basic/random-util.c b/src/basic/random-util.c
+index f7decf6..38f8180 100644
+--- a/src/basic/random-util.c
++++ b/src/basic/random-util.c
+@@ -37,6 +37,7 @@ int rdrand(unsigned long *ret) {
+ 
+ #if defined(__i386__) || defined(__x86_64__)
+         static int have_rdrand = -1;
++        unsigned long v;
+         unsigned char err;
+ 
+         if (have_rdrand < 0) {
+@@ -56,7 +57,7 @@ int rdrand(unsigned long *ret) {
+ 
+         asm volatile("rdrand %0;"
+                      "setc %1"
+-                     : "=r" (*ret),
++                     : "=r" (v),
+                        "=qm" (err));
+ 
+ #if HAS_FEATURE_MEMORY_SANITIZER
+@@ -66,6 +67,18 @@ int rdrand(unsigned long *ret) {
+         if (!err)
+                 return -EAGAIN;
+ 
++        /* Apparently on some AMD CPUs RDRAND will sometimes (after a suspend/resume cycle?) report success
++         * via the carry flag but nonetheless return the same fixed value -1 in all cases. This appears to be
++         * a bad bug in the CPU or firmware. Let's deal with that and work-around this by explicitly checking
++         * for this special value (and also 0, just to be sure) and filtering it out. This is a work-around
++         * only however and something AMD really should fix properly. The Linux kernel should probably work
++         * around this issue by turning off RDRAND altogether on those CPUs. See:
++         * https://github.com/systemd/systemd/issues/11810 */
++        if (v == 0 || v == ULONG_MAX)
++                return log_debug_errno(SYNTHETIC_ERRNO(EUCLEAN),
++                                       "RDRAND returned suspicious value %lx, assuming bad hardware RNG, not using value.", v);
++
++        *ret = v;
+         return 0;
+ #else
+         return -EOPNOTSUPP;