linux-stable.git/arch/x86/include/asm, branch linux-3.10.y

x86/io: Add "memory" clobber to insb/insw/insl/outsb/outsw/outsl

2017-11-02T06:16:25+00:00

commit 7206f9bf108eb9513d170c73f151367a1bdf3dbf upstream.

The x86 version of insb/insw/insl uses an inline assembly that does
not have the target buffer listed as an output. This can confuse
the compiler, leading it to think that a subsequent access of the
buffer is uninitialized:

  drivers/net/wireless/wl3501_cs.c: In function ‘wl3501_mgmt_scan_confirm’:
  drivers/net/wireless/wl3501_cs.c:665:9: error: ‘sig.status’ is used uninitialized in this function [-Werror=uninitialized]
  drivers/net/wireless/wl3501_cs.c:668:12: error: ‘sig.cap_info’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
  drivers/net/sb1000.c: In function 'sb1000_rx':
  drivers/net/sb1000.c:775:9: error: 'st[0]' is used uninitialized in this function [-Werror=uninitialized]
  drivers/net/sb1000.c:776:10: error: 'st[1]' may be used uninitialized in this function [-Werror=maybe-uninitialized]
  drivers/net/sb1000.c:784:11: error: 'st[1]' may be used uninitialized in this function [-Werror=maybe-uninitialized]

I tried to mark the exact input buffer as an output here, but couldn't
figure it out. As suggested by Linus, marking all memory as clobbered
however is good enough too. For the outs operations, I also add the
memory clobber, to force the input to be written to local variables.
This is probably already guaranteed by the "asm volatile", but it can't
hurt to do this for symmetry.

Suggested-by: Linus Torvalds 
Signed-off-by: Arnd Bergmann 
Acked-by: Linus Torvalds 
Cc: Borislav Petkov 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Tom Lendacky 
Link: http://lkml.kernel.org/r/20170719125310.2487451-5-arnd@arndb.de
Link: https://lkml.org/lkml/2017/7/12/605
Signed-off-by: Ingo Molnar 
Signed-off-by: Willy Tarreau

x86/vdso: Plug race between mapping and ELF header setup

2017-06-20T12:04:44+00:00

commit 6fdc6dd90272ce7e75d744f71535cfbd8d77da81 upstream.

The vsyscall32 sysctl can racy against a concurrent fork when it switches
from disabled to enabled:

    arch_setup_additional_pages()
	if (vdso32_enabled)
           --> No mapping
                                        sysctl.vsysscall32()
                                          --> vdso32_enabled = true
    create_elf_tables()
      ARCH_DLINFO_IA32
        if (vdso32_enabled) {
           --> Add VDSO entry with NULL pointer

Make ARCH_DLINFO_IA32 check whether the VDSO mapping has been set up for
the newly forked process or not.

Signed-off-by: Thomas Gleixner 
Acked-by: Andy Lutomirski 
Cc: Peter Zijlstra 
Cc: Mathias Krause 
Link: http://lkml.kernel.org/r/20170410151723.602367196@linutronix.de
Signed-off-by: Thomas Gleixner 
Signed-off-by: Willy Tarreau

Fix potential infoleak in older kernels

2017-02-06T22:33:04+00:00

Not upstream as it is not needed there.

So a patch something like this might be a safe way to fix the
potential infoleak in older kernels.

THIS IS UNTESTED. It's a very obvious patch, though, so if it compiles
it probably works. It just initializes the output variable with 0 in
the inline asm description, instead of doing it in the exception
handler.

It will generate slightly worse code (a few unnecessary ALU
operations), but it doesn't have any interactions with the exception
handler implementation.

Signed-off-by: Jiri Slaby 
Signed-off-by: Willy Tarreau

x86/mm: Disable preemption during CR3 read+write

2017-02-06T22:32:51+00:00

commit 5cf0791da5c162ebc14b01eb01631cfa7ed4fa6e upstream.

There's a subtle preemption race on UP kernels:

Usually current->mm (and therefore mm->pgd) stays the same during the
lifetime of a task so it does not matter if a task gets preempted during
the read and write of the CR3.

But then, there is this scenario on x86-UP:

TaskA is in do_exit() and exit_mm() sets current->mm = NULL followed by:

 -> mmput()
 -> exit_mmap()
 -> tlb_finish_mmu()
 -> tlb_flush_mmu()
 -> tlb_flush_mmu_tlbonly()
 -> tlb_flush()
 -> flush_tlb_mm_range()
 -> __flush_tlb_up()
 -> __flush_tlb()
 ->  __native_flush_tlb()

At this point current->mm is NULL but current->active_mm still points to
the "old" mm.

Let's preempt taskA _after_ native_read_cr3() by taskB. TaskB has its
own mm so CR3 has changed.

Now preempt back to taskA. TaskA has no ->mm set so it borrows taskB's
mm and so CR3 remains unchanged. Once taskA gets active it continues
where it was interrupted and that means it writes its old CR3 value
back. Everything is fine because userland won't need its memory
anymore.

Now the fun part:

Let's preempt taskA one more time and get back to taskB. This
time switch_mm() won't do a thing because oldmm (->active_mm)
is the same as mm (as per context_switch()). So we remain
with a bad CR3 / PGD and return to userland.

The next thing that happens is handle_mm_fault() with an address for
the execution of its code in userland. handle_mm_fault() realizes that
it has a PTE with proper rights so it returns doing nothing. But the
CPU looks at the wrong PGD and insists that something is wrong and
faults again. And again. And one more timeâ¦

This pagefault circle continues until the scheduler gets tired of it and
puts another task on the CPU. It gets little difficult if the task is a
RT task with a high priority. The system will either freeze or it gets
fixed by the software watchdog thread which usually runs at RT-max prio.
But waiting for the watchdog will increase the latency of the RT task
which is no good.

Fix this by disabling preemption across the critical code section.

Signed-off-by: Sebastian Andrzej Siewior 
Acked-by: Peter Zijlstra (Intel) 
Acked-by: Rik van Riel 
Acked-by: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Mel Gorman 
Cc: Peter Zijlstra 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/1470404259-26290-1-git-send-email-bigeasy@linutronix.de
[ Prettified the changelog. ]
Signed-off-by: Ingo Molnar 
Signed-off-by: Willy Tarreau

x86/mm/xen: Suppress hugetlbfs in PV guests

2017-02-06T08:04:07+00:00

commit 103f6112f253017d7062cd74d17f4a514ed4485c upstream.

Huge pages are not normally available to PV guests. Not suppressing
hugetlbfs use results in an endless loop of page faults when user mode
code tries to access a hugetlbfs mapped area (since the hypervisor
denies such PTEs to be created, but error indications can't be
propagated out of xen_set_pte_at(), just like for various of its
siblings), and - once killed in an oops like this:

  kernel BUG at .../fs/hugetlbfs/inode.c:428!
  invalid opcode: 0000 [#1] SMP
  ...
  RIP: e030:[]  [] remove_inode_hugepages+0x25b/0x320
  ...
  Call Trace:
   [] hugetlbfs_evict_inode+0x15/0x40
   [] evict+0xbd/0x1b0
   [] __dentry_kill+0x19a/0x1f0
   [] dput+0x1fe/0x220
   [] __fput+0x155/0x200
   [] task_work_run+0x60/0xa0
   [] do_exit+0x160/0x400
   [] do_group_exit+0x3b/0xa0
   [] get_signal+0x1ed/0x470
   [] do_signal+0x14/0x110
   [] prepare_exit_to_usermode+0xe9/0xf0
   [] retint_user+0x8/0x13

This is CVE-2016-3961 / XSA-174.

Reported-by: Vitaly Kuznetsov 
Signed-off-by: Jan Beulich 
Cc: Andrew Morton 
Cc: Andy Lutomirski 
Cc: Boris Ostrovsky 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: David Vrabel 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Juergen Gross 
Cc: Linus Torvalds 
Cc: Luis R. Rodriguez 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Toshi Kani 
Cc: xen-devel 
Link: http://lkml.kernel.org/r/57188ED802000078000E431C@prv-mh.provo.novell.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Willy Tarreau

x86/mm: Improve switch_mm() barrier comments

2016-08-27T09:40:33+00:00

commit 4eaffdd5a5fe6ff9f95e1ab4de1ac904d5e0fa8b upstream.

My previous comments were still a bit confusing and there was a
typo. Fix it up.

Reported-by: Peter Zijlstra 
Signed-off-by: Andy Lutomirski 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Dave Hansen 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Cc: stable@vger.kernel.org
Fixes: 71b3c126e611 ("x86/mm: Add barriers and document switch_mm()-vs-flush synchronization")
Link: http://lkml.kernel.org/r/0a0b43cdcdd241c5faaaecfbcc91a155ddedc9a1.1452631609.git.luto@kernel.org
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Willy Tarreau

x86/mm: Add barriers and document switch_mm()-vs-flush synchronization

2016-08-21T21:22:36+00:00

commit 71b3c126e61177eb693423f2e18a1914205b165e upstream.

When switch_mm() activates a new PGD, it also sets a bit that
tells other CPUs that the PGD is in use so that TLB flush IPIs
will be sent.  In order for that to work correctly, the bit
needs to be visible prior to loading the PGD and therefore
starting to fill the local TLB.

Document all the barriers that make this work correctly and add
a couple that were missing.

CVE-2016-2069

Signed-off-by: Andy Lutomirski 
Cc: Andrew Morton 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Dave Hansen 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Cc: linux-mm@kvack.org
Signed-off-by: Ingo Molnar 
[ luis: backported to 3.16:
  - dropped N/A comment in flush_tlb_mm_range()
  - adjusted context ]
Signed-off-by: Luis Henriques 
[ciwillia@brocade.com: backported to 3.10: adjusted context]
Signed-off-by: Charles (Chas) Williams 
Signed-off-by: Willy Tarreau

x86: Rename X86_CR4_RDWRGSFS to X86_CR4_FSGSBASE

2016-06-07T08:42:44+00:00

commit afcbf13fa6d53d8a97eafaca1dcb344331d2ce0c upstream.

Rename X86_CR4_RDWRGSFS to X86_CR4_FSGSBASE to match the SDM.

Signed-off-by: H. Peter Anvin 
Cc: Marcelo Tosatti 
Cc: Gleb Natapov 
Link: http://lkml.kernel.org/n/tip-buq1evi5dpykxx7ak6amaam0@git.kernel.org
[wt: backported to 3.10 only to keep next patch clean]

Signed-off-by: Willy Tarreau

x86/iopl/64: Properly context-switch IOPL on Xen PV

2016-06-07T08:42:43+00:00

commit b7a584598aea7ca73140cb87b40319944dd3393f upstream.

From: Andy Lutomirski 

On Xen PV, regs->flags doesn't reliably reflect IOPL and the
exit-to-userspace code doesn't change IOPL.  We need to context
switch it manually.

I'm doing this without going through paravirt because this is
specific to Xen PV.  After the dust settles, we can merge this with
the 32-bit code, tidy up the iopl syscall implementation, and remove
the set_iopl pvop entirely.

Fixes XSA-171.

Reviewewd-by: Jan Beulich 
Signed-off-by: Andy Lutomirski 
Cc: Andrew Cooper 
Cc: Andy Lutomirski 
Cc: Boris Ostrovsky 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: David Vrabel 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Jan Beulich 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/693c3bd7aeb4d3c27c92c622b7d0f554a458173c.1458162709.git.luto@kernel.org
Signed-off-by: Ingo Molnar 
[ kamal: backport to 3.19-stable: no X86_FEATURE_XENPV so just call
  xen_pv_domain() directly ]
Acked-by: Andy Lutomirski 
Signed-off-by: Kamal Mostafa 
Signed-off-by: Willy Tarreau

x86/asm/irq: Stop relying on magic JMP behavior for early_idt_handlers

2016-02-25T19:57:49+00:00

commit 425be5679fd292a3c36cb1fe423086708a99f11a upstream.

The early_idt_handlers asm code generates an array of entry
points spaced nine bytes apart.  It's not really clear from that
code or from the places that reference it what's going on, and
the code only works in the first place because GAS never
generates two-byte JMP instructions when jumping to global
labels.

Clean up the code to generate the correct array stride (member size)
explicitly. This should be considerably more robust against
screw-ups, as GAS will warn if a .fill directive has a negative
count.  Using '. =' to advance would have been even more robust
(it would generate an actual error if it tried to move
backwards), but it would pad with nulls, confusing anyone who
tries to disassemble the code.  The new scheme should be much
clearer to future readers.

While we're at it, improve the comments and rename the array and
common code.

Binutils may start relaxing jumps to non-weak labels.  If so,
this change will fix our build, and we may need to backport this
change.

Before, on x86_64:

  0000000000000000 :
     0:   6a 00                   pushq  $0x0
     2:   6a 00                   pushq  $0x0
     4:   e9 00 00 00 00          jmpq   9 
                          5: R_X86_64_PC32        early_idt_handler-0x4
  ...
    48:   66 90                   xchg   %ax,%ax
    4a:   6a 08                   pushq  $0x8
    4c:   e9 00 00 00 00          jmpq   51 
                          4d: R_X86_64_PC32       early_idt_handler-0x4
  ...
   117:   6a 00                   pushq  $0x0
   119:   6a 1f                   pushq  $0x1f
   11b:   e9 00 00 00 00          jmpq   120 
                          11c: R_X86_64_PC32      early_idt_handler-0x4

After:

  0000000000000000 :
     0:   6a 00                   pushq  $0x0
     2:   6a 00                   pushq  $0x0
     4:   e9 14 01 00 00          jmpq   11d 
  ...
    48:   6a 08                   pushq  $0x8
    4a:   e9 d1 00 00 00          jmpq   120 
    4f:   cc                      int3
    50:   cc                      int3
  ...
   117:   6a 00                   pushq  $0x0
   119:   6a 1f                   pushq  $0x1f
   11b:   eb 03                   jmp    120 
   11d:   cc                      int3
   11e:   cc                      int3
   11f:   cc                      int3

Signed-off-by: Andy Lutomirski 
Acked-by: H. Peter Anvin 
Cc: Binutils 
Cc: Borislav Petkov 
Cc: H.J. Lu 
Cc: Jan Beulich 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/ac027962af343b0c599cbfcf50b945ad2ef3d7a8.1432336324.git.luto@kernel.org
Signed-off-by: Ingo Molnar 
Signed-off-by: Jiri Slaby 
Signed-off-by: Greg Kroah-Hartman