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systemd: eat up RDRAND values seen on AMD cpus

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MilhouseVH 2019-07-09 18:24:09 +01:00
parent 266954d8b0
commit 8dbe022c96
1 changed files with 138 additions and 0 deletions
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138
packages/sysutils/systemd/patches/systemd-0400-eat-up-rrdrand-on-amd.patch Normal file
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@ -0,0 +1,138 @@
From 0c0e3b8ec413a5b8151ad111b08c84ad07f1891b Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 7 May 2019 18:51:26 -0400
Subject: [PATCH 1/3] random-util: rename "err" to "success"
After all rdrand returns 1 on success, and 0 on failure, hence let's
name this accordingly.
---
src/basic/random-util.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/src/basic/random-util.c b/src/basic/random-util.c
index ca25fd2..f992c0c 100644
--- a/src/basic/random-util.c
+++ b/src/basic/random-util.c
@@ -34,7 +34,7 @@ int rdrand(unsigned long *ret) {
#if defined(__i386__) || defined(__x86_64__)
static int have_rdrand = -1;
- unsigned char err;
+ uint8_t success;
if (have_rdrand < 0) {
uint32_t eax, ebx, ecx, edx;
@@ -54,9 +54,9 @@ int rdrand(unsigned long *ret) {
asm volatile("rdrand %0;"
"setc %1"
: "=r" (*ret),
- "=qm" (err));
- msan_unpoison(&err, sizeof(err));
- if (!err)
+ "=qm" (success));
+ msan_unpoison(&success, sizeof(sucess));
+ if (!success)
return -EAGAIN;
return 0;
--
2.14.1
From 78b5b76ad2c82a9d184dfa777ac116bdf22189eb Mon Sep 17 00:00:00 2001
From: Evgeny Vereshchagin <evvers@ya.ru>
Date: Wed, 8 May 2019 15:50:53 +0200
Subject: [PATCH 2/3] util-lib: fix a typo in rdrand
Otherwise, the fuzzers will fail to compile with MSan:
```
../../src/systemd/src/basic/random-util.c:64:40: error: use of undeclared identifier 'sucess'; did you mean 'success'?
msan_unpoison(&success, sizeof(sucess));
^~~~~~
success
../../src/systemd/src/basic/alloc-util.h:169:50: note: expanded from macro 'msan_unpoison'
^
../../src/systemd/src/basic/random-util.c:38:17: note: 'success' declared here
uint8_t success;
^
1 error generated.
[80/545] Compiling C object 'src/basic/a6ba3eb@@basic@sta/process-util.c.o'.
ninja: build stopped: subcommand failed.
Fuzzers build failed
```
---
src/basic/random-util.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/basic/random-util.c b/src/basic/random-util.c
index f992c0c..d67aa09 100644
--- a/src/basic/random-util.c
+++ b/src/basic/random-util.c
@@ -55,7 +55,7 @@ int rdrand(unsigned long *ret) {
"setc %1"
: "=r" (*ret),
"=qm" (success));
- msan_unpoison(&success, sizeof(sucess));
+ msan_unpoison(&success, sizeof(success));
if (!success)
return -EAGAIN;
--
2.14.1
From b0497c3005cc3a7975362d7e70d9ae2d0ffa6154 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 10 May 2019 15:16:16 -0400
Subject: [PATCH 3/3] 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
---
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 d67aa09..bd148ee 100644
--- a/src/basic/random-util.c
+++ b/src/basic/random-util.c
@@ -34,6 +34,7 @@ int rdrand(unsigned long *ret) {
#if defined(__i386__) || defined(__x86_64__)
static int have_rdrand = -1;
+ unsigned long v;
uint8_t success;
if (have_rdrand < 0) {
@@ -53,12 +54,24 @@ int rdrand(unsigned long *ret) {
asm volatile("rdrand %0;"
"setc %1"
- : "=r" (*ret),
+ : "=r" (v),
"=qm" (success));
msan_unpoison(&success, sizeof(success));
if (!success)
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;
--
2.14.1