130 lines
4.4 KiB
Diff
130 lines
4.4 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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Date: Mon, 4 Dec 2017 15:07:07 +0100
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Subject: [PATCH] x86/entry/64/paravirt: Use paravirt-safe macro to access
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eflags
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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CVE-2017-5754
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Commit 1d3e53e8624a ("x86/entry/64: Refactor IRQ stacks and make them
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NMI-safe") added DEBUG_ENTRY_ASSERT_IRQS_OFF macro that acceses eflags
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using 'pushfq' instruction when testing for IF bit. On PV Xen guests
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looking at IF flag directly will always see it set, resulting in 'ud2'.
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Introduce SAVE_FLAGS() macro that will use appropriate save_fl pv op when
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running paravirt.
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Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Reviewed-by: Juergen Gross <jgross@suse.com>
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Cc: Andy Lutomirski <luto@kernel.org>
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Cc: Borislav Petkov <bp@alien8.de>
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Cc: Borislav Petkov <bpetkov@suse.de>
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Cc: Brian Gerst <brgerst@gmail.com>
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Cc: Dave Hansen <dave.hansen@intel.com>
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Cc: Dave Hansen <dave.hansen@linux.intel.com>
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Cc: David Laight <David.Laight@aculab.com>
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Cc: Denys Vlasenko <dvlasenk@redhat.com>
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Cc: Eduardo Valentin <eduval@amazon.com>
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Cc: Greg KH <gregkh@linuxfoundation.org>
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Cc: H. Peter Anvin <hpa@zytor.com>
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Cc: Josh Poimboeuf <jpoimboe@redhat.com>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>
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Cc: Peter Zijlstra <peterz@infradead.org>
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Cc: Rik van Riel <riel@redhat.com>
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Cc: Will Deacon <will.deacon@arm.com>
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Cc: aliguori@amazon.com
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Cc: daniel.gruss@iaik.tugraz.at
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Cc: hughd@google.com
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Cc: keescook@google.com
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Cc: xen-devel@lists.xenproject.org
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Link: https://lkml.kernel.org/r/20171204150604.899457242@linutronix.de
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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(cherry picked from commit e17f8234538d1ff708673f287a42457c4dee720d)
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Signed-off-by: Andy Whitcroft <apw@canonical.com>
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Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
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(cherry picked from commit 9f4a274842938ce8d55565ced4f45e7ad4a5da90)
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Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
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---
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arch/x86/include/asm/irqflags.h | 3 +++
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arch/x86/include/asm/paravirt.h | 9 +++++++++
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arch/x86/kernel/asm-offsets_64.c | 3 +++
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arch/x86/entry/entry_64.S | 7 ++++---
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4 files changed, 19 insertions(+), 3 deletions(-)
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diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h
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index ac7692dcfa2e..d937781e1047 100644
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--- a/arch/x86/include/asm/irqflags.h
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+++ b/arch/x86/include/asm/irqflags.h
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@@ -141,6 +141,9 @@ static inline notrace unsigned long arch_local_irq_save(void)
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swapgs; \
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sysretl
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+#ifdef CONFIG_DEBUG_ENTRY
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+#define SAVE_FLAGS(x) pushfq; popq %rax
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+#endif
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#else
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#define INTERRUPT_RETURN iret
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#define ENABLE_INTERRUPTS_SYSEXIT sti; sysexit
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diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
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index 43d4f90edebc..52dcd2361a78 100644
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--- a/arch/x86/include/asm/paravirt.h
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+++ b/arch/x86/include/asm/paravirt.h
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@@ -926,6 +926,15 @@ extern void default_banner(void);
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PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_usergs_sysret64), \
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CLBR_NONE, \
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jmp PARA_INDIRECT(pv_cpu_ops+PV_CPU_usergs_sysret64))
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+
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+#ifdef CONFIG_DEBUG_ENTRY
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+#define SAVE_FLAGS(clobbers) \
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+ PARA_SITE(PARA_PATCH(pv_irq_ops, PV_IRQ_save_fl), clobbers, \
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+ PV_SAVE_REGS(clobbers | CLBR_CALLEE_SAVE); \
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+ call PARA_INDIRECT(pv_irq_ops+PV_IRQ_save_fl); \
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+ PV_RESTORE_REGS(clobbers | CLBR_CALLEE_SAVE);)
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+#endif
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+
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#endif /* CONFIG_X86_32 */
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#endif /* __ASSEMBLY__ */
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diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
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index cf42206926af..c21a5315b38e 100644
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--- a/arch/x86/kernel/asm-offsets_64.c
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+++ b/arch/x86/kernel/asm-offsets_64.c
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@@ -22,6 +22,9 @@ int main(void)
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#ifdef CONFIG_PARAVIRT
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OFFSET(PV_CPU_usergs_sysret64, pv_cpu_ops, usergs_sysret64);
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OFFSET(PV_CPU_swapgs, pv_cpu_ops, swapgs);
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+#ifdef CONFIG_DEBUG_ENTRY
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+ OFFSET(PV_IRQ_save_fl, pv_irq_ops, save_fl);
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+#endif
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BLANK();
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#endif
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diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
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index 2491b3b25b9a..6c73e96daf78 100644
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--- a/arch/x86/entry/entry_64.S
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+++ b/arch/x86/entry/entry_64.S
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@@ -461,12 +461,13 @@ END(irq_entries_start)
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.macro DEBUG_ENTRY_ASSERT_IRQS_OFF
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#ifdef CONFIG_DEBUG_ENTRY
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- pushfq
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- testl $X86_EFLAGS_IF, (%rsp)
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+ pushq %rax
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+ SAVE_FLAGS(CLBR_RAX)
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+ testl $X86_EFLAGS_IF, %eax
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jz .Lokay_\@
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ud2
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.Lokay_\@:
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- addq $8, %rsp
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+ popq %rax
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#endif
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.endm
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--
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2.14.2
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