From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org, Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Fenghua Yu <fenghua.yu@intel.com>,
Tony Luck <tony.luck@intel.com>,
Yu-cheng Yu <yu-cheng.yu@intel.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
syzbot+2067e764dbcd10721e2e@syzkaller.appspotmail.com,
Borislav Petkov <bp@suse.de>, Rik van Riel <riel@surriel.com>
Subject: [patch V3 6/6] selftests/x86: Test signal frame XSTATE header corruption handling
Date: Tue, 08 Jun 2021 16:36:23 +0200 [thread overview]
Message-ID: <20210608144346.234764986@linutronix.de> (raw)
In-Reply-To: 20210608143617.565868844@linutronix.de
From: Andy Lutomirski <luto@kernel.org>
This is very heavily based on some code from Thomas Gleixner. On a system
without XSAVES, it triggers the WARN_ON():
Bad FPU state detected at copy_kernel_to_fpregs+0x2f/0x40, reinitializing FPU registers.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
V2: main() -> main(void) - Borislav
---
tools/testing/selftests/x86/Makefile | 3
tools/testing/selftests/x86/corrupt_xstate_header.c | 114 ++++++++++++++++++++
2 files changed, 116 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/x86/corrupt_xstate_header.c
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -17,7 +17,8 @@ TARGETS_C_BOTHBITS := single_step_syscal
TARGETS_C_32BIT_ONLY := entry_from_vm86 test_syscall_vdso unwind_vdso \
test_FCMOV test_FCOMI test_FISTTP \
vdso_restorer
-TARGETS_C_64BIT_ONLY := fsgsbase sysret_rip syscall_numbering
+TARGETS_C_64BIT_ONLY := fsgsbase sysret_rip syscall_numbering \
+ corrupt_xstate_header
# Some selftests require 32bit support enabled also on 64bit systems
TARGETS_C_32BIT_NEEDED := ldt_gdt ptrace_syscall
--- /dev/null
+++ b/tools/testing/selftests/x86/corrupt_xstate_header.c
@@ -0,0 +1,114 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Corrupt the XSTATE header in a signal frame
+ *
+ * Based on analysis and a test case from Thomas Gleixner.
+ */
+
+#define _GNU_SOURCE
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <sched.h>
+#include <signal.h>
+#include <err.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <sys/wait.h>
+
+static inline void __cpuid(unsigned int *eax, unsigned int *ebx,
+ unsigned int *ecx, unsigned int *edx)
+{
+ asm volatile(
+ "cpuid;"
+ : "=a" (*eax),
+ "=b" (*ebx),
+ "=c" (*ecx),
+ "=d" (*edx)
+ : "0" (*eax), "2" (*ecx));
+}
+
+static inline int xsave_enabled(void)
+{
+ unsigned int eax, ebx, ecx, edx;
+
+ eax = 0x1;
+ ecx = 0x0;
+ __cpuid(&eax, &ebx, &ecx, &edx);
+
+ /* Is CR4.OSXSAVE enabled ? */
+ return ecx & (1U << 27);
+}
+
+static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
+ int flags)
+{
+ struct sigaction sa;
+
+ memset(&sa, 0, sizeof(sa));
+ sa.sa_sigaction = handler;
+ sa.sa_flags = SA_SIGINFO | flags;
+ sigemptyset(&sa.sa_mask);
+ if (sigaction(sig, &sa, 0))
+ err(1, "sigaction");
+}
+
+static void sigusr1(int sig, siginfo_t *info, void *uc_void)
+{
+ ucontext_t *uc = uc_void;
+ uint8_t *fpstate = (uint8_t *)uc->uc_mcontext.fpregs;
+ uint64_t *xfeatures = (uint64_t *)(fpstate + 512);
+
+ printf("\tWreckage XSTATE header\n");
+ /* Wreckage the first reserved byte in the header */
+ *(xfeatures + 2) = 0xfffffff;
+}
+
+static void sigsegv(int sig, siginfo_t *info, void *uc_void)
+{
+ printf("\tGot SIGSEGV\n");
+}
+
+int main(void)
+{
+ cpu_set_t set;
+
+ sethandler(SIGUSR1, sigusr1, 0);
+ sethandler(SIGSEGV, sigsegv, 0);
+
+ if (!xsave_enabled()) {
+ printf("[SKIP] CR4.OSXSAVE disabled.\n");
+ return 0;
+ }
+
+ CPU_ZERO(&set);
+ CPU_SET(0, &set);
+
+ /*
+ * Enforce that the child runs on the same CPU
+ * which in turn forces a schedule.
+ */
+ sched_setaffinity(getpid(), sizeof(set), &set);
+
+ printf("[RUN]\tSend ourselves a signal\n");
+ raise(SIGUSR1);
+
+ printf("[OK]\tBack from the signal. Now schedule.\n");
+ pid_t child = fork();
+ if (child < 0)
+ err(1, "fork");
+ if (child == 0)
+ return 0;
+ if (child)
+ waitpid(child, NULL, 0);
+ printf("[OK]\tBack in the main thread.\n");
+
+ /*
+ * We could try to confirm that extended state is still preserved
+ * when we schedule. For now, the only indication of failure is
+ * a warning in the kernel logs.
+ */
+
+ return 0;
+}
next prev parent reply other threads:[~2021-06-08 14:49 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-08 14:36 [patch V3 0/6] x86/fpu: Mop up XSAVES and related damage Thomas Gleixner
2021-06-08 14:36 ` [patch V3 1/6] x86/fpu: Prevent state corruption in __fpu__restore_sig() Thomas Gleixner
2021-06-09 14:46 ` [tip: x86/urgent] " tip-bot2 for Thomas Gleixner
2021-06-08 14:36 ` [patch V3 2/6] x86/fpu: Invalidate FPU state after a failed XRSTOR from a user buffer Thomas Gleixner
2021-06-09 14:46 ` [tip: x86/urgent] " tip-bot2 for Andy Lutomirski
2021-06-08 14:36 ` [patch V3 3/6] x86/process: Check PF_KTHREAD and not current->mm for kernel threads Thomas Gleixner
2021-06-09 14:46 ` [tip: x86/urgent] " tip-bot2 for Thomas Gleixner
2021-06-10 17:10 ` [patch V3 3/6] " Andy Lutomirski
2021-06-10 20:54 ` Thomas Gleixner
2021-06-11 1:04 ` Andy Lutomirski
2021-06-08 14:36 ` [patch V3 4/6] x86/pkru: Make PKRU=0 actually work Thomas Gleixner
2021-06-08 15:40 ` Borislav Petkov
2021-06-08 19:15 ` Thomas Gleixner
2021-06-08 20:06 ` Borislav Petkov
2021-06-08 16:06 ` Dave Hansen
2021-06-08 19:06 ` Thomas Gleixner
2021-06-08 21:37 ` Babu Moger
2021-06-09 14:46 ` [tip: x86/urgent] x86/pkru: Write hardware init value to PKRU when xstate is init tip-bot2 for Thomas Gleixner
2021-06-08 14:36 ` [patch V3 5/6] x86/fpu: Add address range checks to copy_user_to_xstate() Thomas Gleixner
2021-06-09 12:56 ` [tip: x86/fpu] " tip-bot2 for Andy Lutomirski
2021-06-08 14:36 ` Thomas Gleixner [this message]
2021-06-09 8:38 ` [patch V3 6/6] selftests/x86: Test signal frame XSTATE header corruption handling David Edmondson
2021-06-09 12:56 ` [tip: x86/fpu] " tip-bot2 for Andy Lutomirski
2021-06-08 16:08 ` [patch V3 0/6] x86/fpu: Mop up XSAVES and related damage Dave Hansen
2021-06-08 18:46 ` Rik van Riel
2021-06-09 19:18 ` [PATCH] x86/fpu: Reset state for all signal restore failures Thomas Gleixner
2021-06-10 6:39 ` [tip: x86/urgent] " tip-bot2 for Thomas Gleixner
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