projects / pve-kernel.git / blame
| Commit | Line | Data |
|---|---|---|
| 321d628a FG |
1 | From ee46485b45de9c2008e3ef5f847041fc18743052 Mon Sep 17 00:00:00 2001 |
| 2 | From: Thomas Gleixner <tglx@linutronix.de> | |
| 3 | Date: Wed, 3 Jan 2018 19:52:04 +0100 | |
| e4cdf2a5 | 4 | Subject: [PATCH 225/241] x86/pti: Switch to kernel CR3 at early in |
| 321d628a FG |
5 | entry_SYSCALL_compat() |
| 6 | MIME-Version: 1.0 | |
| 7 | Content-Type: text/plain; charset=UTF-8 | |
| 8 | Content-Transfer-Encoding: 8bit | |
| 9 | ||
| 10 | CVE-2017-5754 | |
| 11 | ||
| 12 | The preparation for PTI which added CR3 switching to the entry code | |
| 13 | misplaced the CR3 switch in entry_SYSCALL_compat(). | |
| 14 | ||
| 15 | With PTI enabled the entry code tries to access a per cpu variable after | |
| 16 | switching to kernel GS. This fails because that variable is not mapped to | |
| 17 | user space. This results in a double fault and in the worst case a kernel | |
| 18 | crash. | |
| 19 | ||
| 20 | Move the switch ahead of the access and clobber RSP which has been saved | |
| 21 | already. | |
| 22 | ||
| 23 | Fixes: 8a09317b895f ("x86/mm/pti: Prepare the x86/entry assembly code for entry/exit CR3 switching") | |
| 24 | Reported-by: Lars Wendler <wendler.lars@web.de> | |
| 25 | Reported-by: Laura Abbott <labbott@redhat.com> | |
| 26 | Signed-off-by: Thomas Gleixner <tglx@linutronix.de> | |
| 27 | Cc: Borislav Betkov <bp@alien8.de> | |
| 28 | Cc: Andy Lutomirski <luto@kernel.org>, | |
| 29 | Cc: Dave Hansen <dave.hansen@linux.intel.com>, | |
| 30 | Cc: Peter Zijlstra <peterz@infradead.org>, | |
| 31 | Cc: Greg KH <gregkh@linuxfoundation.org>, , | |
| 32 | Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>, | |
| 33 | Cc: Juergen Gross <jgross@suse.com> | |
| 34 | Cc: stable@vger.kernel.org | |
| 35 | Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1801031949200.1957@nanos | |
| 36 | Signed-off-by: Andy Whitcroft <apw@canonical.com> | |
| 37 | Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com> | |
| 38 | (cherry picked from commit 2f45cd7a57da0a4d7f3a91a5f577c76b9ed9eb8a) | |
| 39 | Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com> | |
| 40 | --- | |
| 41 | arch/x86/entry/entry_64_compat.S | 13 ++++++------- | |
| 42 | 1 file changed, 6 insertions(+), 7 deletions(-) | |
| 43 | ||
| 44 | diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S | |
| 45 | index 973527e34887..2b5e7685823c 100644 | |
| 46 | --- a/arch/x86/entry/entry_64_compat.S | |
| 47 | +++ b/arch/x86/entry/entry_64_compat.S | |
| 48 | @@ -189,8 +189,13 @@ ENTRY(entry_SYSCALL_compat) | |
| 49 | /* Interrupts are off on entry. */ | |
| 50 | swapgs | |
| 51 | ||
| 52 | - /* Stash user ESP and switch to the kernel stack. */ | |
| 53 | + /* Stash user ESP.*/ | |
| 54 | movl %esp, %r8d | |
| 55 | + | |
| 56 | + /* Use %rsp as scratch reg. User ESP is stashed in r8 */ | |
| 57 | + SWITCH_TO_KERNEL_CR3 scratch_reg=%rsp | |
| 58 | + | |
| 59 | + /* Switch to the kernel stack */ | |
| 60 | movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp | |
| 61 | ||
| 62 | /* Construct struct pt_regs on stack */ | |
| 63 | @@ -218,12 +223,6 @@ GLOBAL(entry_SYSCALL_compat_after_hwframe) | |
| 64 | pushq $0 /* pt_regs->r14 = 0 */ | |
| 65 | pushq $0 /* pt_regs->r15 = 0 */ | |
| 66 | ||
| 67 | - /* | |
| 68 | - * We just saved %rdi so it is safe to clobber. It is not | |
| 69 | - * preserved during the C calls inside TRACE_IRQS_OFF anyway. | |
| 70 | - */ | |
| 71 | - SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi | |
| 72 | - | |
| 73 | /* | |
| 74 | * User mode is traced as though IRQs are on, and SYSENTER | |
| 75 | * turned them off. | |
| 76 | -- | |
| 77 | 2.14.2 | |
| 78 |