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authorThomas Garnier <thgarnie@google.com>2017-03-14 10:05:07 -0700
committerIngo Molnar <mingo@kernel.org>2017-03-16 09:06:35 +0100
commit69218e47994da614e7af600bf06887750ab6657a (patch)
treec1399085e63a1b42cda253a73a0d33b1e84cb864 /drivers/pnp
parentf06bdd4001c257792c54dce9427399f2896470af (diff)
x86: Remap GDT tables in the fixmap section
Each processor holds a GDT in its per-cpu structure. The sgdt instruction gives the base address of the current GDT. This address can be used to bypass KASLR memory randomization. With another bug, an attacker could target other per-cpu structures or deduce the base of the main memory section (PAGE_OFFSET). This patch relocates the GDT table for each processor inside the fixmap section. The space is reserved based on number of supported processors. For consistency, the remapping is done by default on 32 and 64-bit. Each processor switches to its remapped GDT at the end of initialization. For hibernation, the main processor returns with the original GDT and switches back to the remapping at completion. This patch was tested on both architectures. Hibernation and KVM were both tested specially for their usage of the GDT. Thanks to Boris Ostrovsky <boris.ostrovsky@oracle.com> for testing and recommending changes for Xen support. Signed-off-by: Thomas Garnier <thgarnie@google.com> Cc: Alexander Potapenko <glider@google.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Borislav Petkov <bp@suse.de> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Jiri Kosina <jikos@kernel.org> Cc: Joerg Roedel <joro@8bytes.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: Kees Cook <keescook@chromium.org> Cc: Len Brown <len.brown@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Lorenzo Stoakes <lstoakes@gmail.com> Cc: Luis R . Rodriguez <mcgrof@kernel.org> Cc: Matt Fleming <matt@codeblueprint.co.uk> Cc: Michal Hocko <mhocko@suse.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Pavel Machek <pavel@ucw.cz> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Rafael J . Wysocki <rjw@rjwysocki.net> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Stanislaw Gruszka <sgruszka@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: kasan-dev@googlegroups.com Cc: kernel-hardening@lists.openwall.com Cc: kvm@vger.kernel.org Cc: lguest@lists.ozlabs.org Cc: linux-doc@vger.kernel.org Cc: linux-efi@vger.kernel.org Cc: linux-mm@kvack.org Cc: linux-pm@vger.kernel.org Cc: xen-devel@lists.xenproject.org Cc: zijun_hu <zijun_hu@htc.com> Link: http://lkml.kernel.org/r/20170314170508.100882-2-thgarnie@google.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'drivers/pnp')
-rw-r--r--drivers/pnp/pnpbios/bioscalls.c10
1 files changed, 5 insertions, 5 deletions
diff --git a/drivers/pnp/pnpbios/bioscalls.c b/drivers/pnp/pnpbios/bioscalls.c
index 438d4c72c7b3..ff563db025b3 100644
--- a/drivers/pnp/pnpbios/bioscalls.c
+++ b/drivers/pnp/pnpbios/bioscalls.c
@@ -54,7 +54,7 @@ __asm__(".text \n"
#define Q2_SET_SEL(cpu, selname, address, size) \
do { \
- struct desc_struct *gdt = get_cpu_gdt_table((cpu)); \
+ struct desc_struct *gdt = get_cpu_gdt_rw((cpu)); \
set_desc_base(&gdt[(selname) >> 3], (u32)(address)); \
set_desc_limit(&gdt[(selname) >> 3], (size) - 1); \
} while(0)
@@ -95,8 +95,8 @@ static inline u16 call_pnp_bios(u16 func, u16 arg1, u16 arg2, u16 arg3,
return PNP_FUNCTION_NOT_SUPPORTED;
cpu = get_cpu();
- save_desc_40 = get_cpu_gdt_table(cpu)[0x40 / 8];
- get_cpu_gdt_table(cpu)[0x40 / 8] = bad_bios_desc;
+ save_desc_40 = get_cpu_gdt_rw(cpu)[0x40 / 8];
+ get_cpu_gdt_rw(cpu)[0x40 / 8] = bad_bios_desc;
/* On some boxes IRQ's during PnP BIOS calls are deadly. */
spin_lock_irqsave(&pnp_bios_lock, flags);
@@ -134,7 +134,7 @@ static inline u16 call_pnp_bios(u16 func, u16 arg1, u16 arg2, u16 arg3,
:"memory");
spin_unlock_irqrestore(&pnp_bios_lock, flags);
- get_cpu_gdt_table(cpu)[0x40 / 8] = save_desc_40;
+ get_cpu_gdt_rw(cpu)[0x40 / 8] = save_desc_40;
put_cpu();
/* If we get here and this is set then the PnP BIOS faulted on us. */
@@ -477,7 +477,7 @@ void pnpbios_calls_init(union pnp_bios_install_struct *header)
pnp_bios_callpoint.segment = PNP_CS16;
for_each_possible_cpu(i) {
- struct desc_struct *gdt = get_cpu_gdt_table(i);
+ struct desc_struct *gdt = get_cpu_gdt_rw(i);
if (!gdt)
continue;
set_desc_base(&gdt[GDT_ENTRY_PNPBIOS_CS32],

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