132 lines
3.6 KiB
Diff
132 lines
3.6 KiB
Diff
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From eec4df641cbce416c86f2e7d6c740d85b8906451 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Bj=C3=B6rn=20Esser?= <besser82@fedoraproject.org>
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Date: Mon, 25 May 2020 13:03:31 +0200
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Subject: [PATCH] Detect broken RDRAND during initialization.
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Some CPUs advertise RDRAND in CPUID, but return
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0xFFFFFFFF unconditionally. To avoid locking up
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later, test RDRAND during initialization, and if
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it returns 0xFFFFFFFF, mark it as nonexistent.
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Also fix a possible segmentation fault in CPUID check.
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This commit is a squashed backport of the following
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commits on the master branch:
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* 0e5bbcaa162ac7850eb4fcd8f91391837d0efb50
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* 4d36b0287d3ab0912ba8a4790340ca099960b2b0
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* 80863140263be5f2dc630938ed8f0066f8a1ab43
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---
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random_seed.c | 66 ++++++++++++++++++++++++++++++++++++++-------------
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1 file changed, 49 insertions(+), 17 deletions(-)
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diff --git a/random_seed.c b/random_seed.c
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index fc19e26d13..b5f8a0795e 100644
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--- a/random_seed.c
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+++ b/random_seed.c
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@@ -26,19 +26,8 @@
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static void do_cpuid(int regs[], int h)
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{
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/* clang-format off */
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- __asm__ __volatile__(
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-#if defined __x86_64__
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- "pushq %%rbx;\n"
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-#else
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- "pushl %%ebx;\n"
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-#endif
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- "cpuid;\n"
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-#if defined __x86_64__
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- "popq %%rbx;\n"
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-#else
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- "popl %%ebx;\n"
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-#endif
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- : "=a"(regs[0]), [ebx] "=r"(regs[1]), "=c"(regs[2]), "=d"(regs[3])
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+ __asm__ __volatile__("cpuid"
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+ : "=a"(regs[0]), "=b"(regs[1]), "=c"(regs[2]), "=d"(regs[3])
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: "a"(h));
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/* clang-format on */
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}
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@@ -54,12 +43,51 @@ static void do_cpuid(int regs[], int h)
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#if HAS_X86_CPUID
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+static int get_rdrand_seed(void);
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+
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+/* Valid values are -1 (haven't tested), 0 (no), and 1 (yes). */
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+static int _has_rdrand = -1;
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+
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static int has_rdrand(void)
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{
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- // CPUID.01H:ECX.RDRAND[bit 30] == 1
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+ if (_has_rdrand != -1)
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+ {
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+ return _has_rdrand;
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+ }
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+
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+ /* CPUID.01H:ECX.RDRAND[bit 30] == 1 */
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int regs[4];
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do_cpuid(regs, 1);
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- return (regs[2] & (1 << 30)) != 0;
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+ if (!(regs[2] & (1 << 30)))
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+ {
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+ _has_rdrand = 0;
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+ return 0;
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+ }
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+
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+ /*
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+ * Some CPUs advertise RDRAND in CPUID, but return 0xFFFFFFFF
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+ * unconditionally. To avoid locking up later, test RDRAND here. If over
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+ * 3 trials RDRAND has returned the same value, declare it broken.
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+ * Example CPUs are AMD Ryzen 3000 series
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+ * and much older AMD APUs, such as the E1-1500
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+ * https://github.com/systemd/systemd/issues/11810
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+ * https://linuxreviews.org/RDRAND_stops_returning_random_values_on_older_AMD_CPUs_after_suspend
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+ */
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+ _has_rdrand = 0;
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+ int prev = get_rdrand_seed();
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+ for (int i = 0; i < 3; i++)
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+ {
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+ int temp = get_rdrand_seed();
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+ if (temp != prev)
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+ {
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+ _has_rdrand = 1;
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+ break;
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+ }
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+
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+ prev = temp;
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+ }
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+
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+ return _has_rdrand;
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}
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#endif
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@@ -74,7 +102,7 @@ static int get_rdrand_seed(void)
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{
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DEBUG_SEED("get_rdrand_seed");
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int _eax;
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- // rdrand eax
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+ /* rdrand eax */
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/* clang-format off */
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__asm__ __volatile__("1: .byte 0x0F\n"
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" .byte 0xC7\n"
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@@ -114,7 +142,7 @@ static int get_rdrand_seed(void)
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DEBUG_SEED("get_rdrand_seed");
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int _eax;
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retry:
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- // rdrand eax
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+ /* rdrand eax */
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__asm _emit 0x0F __asm _emit 0xC7 __asm _emit 0xF0
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__asm jnc retry
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__asm mov _eax, eax
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@@ -188,6 +216,10 @@ static int get_dev_random_seed(void)
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/* clang-format off */
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#include <windows.h>
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+
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+/* Caution: these blank lines must remain so clang-format doesn't reorder
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+ includes to put windows.h after wincrypt.h */
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+
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#include <wincrypt.h>
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/* clang-format on */
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#ifndef __GNUC__
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