linux-stable.git/arch/x86/kernel/process_64.c, branch linux-4.1.y

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

2016-04-18T12:50:32+00:00

commit b7a584598aea7ca73140cb87b40319944dd3393f upstream.

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 4.2-stable: no X86_FEATURE_XENPV so just call
  xen_pv_domain() directly ]
Acked-by: Andy Lutomirski 
Signed-off-by: Kamal Mostafa 
Signed-off-by: Sasha Levin

x86/process: Add proper bound checks in 64bit get_wchan()

2015-10-22T21:43:14+00:00

commit eddd3826a1a0190e5235703d1e666affa4d13b96 upstream.

Dmitry Vyukov reported the following using trinity and the memory
error detector AddressSanitizer
(https://code.google.com/p/address-sanitizer/wiki/AddressSanitizerForKernel).

[ 124.575597] ERROR: AddressSanitizer: heap-buffer-overflow on
address ffff88002e280000
[ 124.576801] ffff88002e280000 is located 131938492886538 bytes to
the left of 28857600-byte region [ffffffff81282e0a, ffffffff82e0830a)
[ 124.578633] Accessed by thread T10915:
[ 124.579295] inlined in describe_heap_address
./arch/x86/mm/asan/report.c:164
[ 124.579295] #0 ffffffff810dd277 in asan_report_error
./arch/x86/mm/asan/report.c:278
[ 124.580137] #1 ffffffff810dc6a0 in asan_check_region
./arch/x86/mm/asan/asan.c:37
[ 124.581050] #2 ffffffff810dd423 in __tsan_read8 ??:0
[ 124.581893] #3 ffffffff8107c093 in get_wchan
./arch/x86/kernel/process_64.c:444

The address checks in the 64bit implementation of get_wchan() are
wrong in several ways:

 - The lower bound of the stack is not the start of the stack
   page. It's the start of the stack page plus sizeof (struct
   thread_info)

 - The upper bound must be:

       top_of_stack - TOP_OF_KERNEL_STACK_PADDING - 2 * sizeof(unsigned long).

   The 2 * sizeof(unsigned long) is required because the stack pointer
   points at the frame pointer. The layout on the stack is: ... IP FP
   ... IP FP. So we need to make sure that both IP and FP are in the
   bounds.

Fix the bound checks and get rid of the mix of numeric constants, u64
and unsigned long. Making all unsigned long allows us to use the same
function for 32bit as well.

Use READ_ONCE() when accessing the stack. This does not prevent a
concurrent wakeup of the task and the stack changing, but at least it
avoids TOCTOU.

Also check task state at the end of the loop. Again that does not
prevent concurrent changes, but it avoids walking for nothing.

Add proper comments while at it.

Reported-by: Dmitry Vyukov 
Reported-by: Sasha Levin 
Based-on-patch-from: Wolfram Gloger 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Borislav Petkov 
Reviewed-by: Dmitry Vyukov 
Cc: Andrey Ryabinin 
Cc: Andy Lutomirski 
Cc: Andrey Konovalov 
Cc: Kostya Serebryany 
Cc: Alexander Potapenko 
Cc: kasan-dev 
Cc: Denys Vlasenko 
Cc: Andi Kleen 
Cc: Wolfram Gloger 
Link: http://lkml.kernel.org/r/20150930083302.694788319@linutronix.de
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

x86/ldt: Make modify_ldt synchronous

2015-09-21T17:05:25+00:00

commit 37868fe113ff2ba814b3b4eb12df214df555f8dc upstream.

modify_ldt() has questionable locking and does not synchronize
threads.  Improve it: redesign the locking and synchronize all
threads' LDTs using an IPI on all modifications.

This will dramatically slow down modify_ldt in multithreaded
programs, but there shouldn't be any multithreaded programs that
care about modify_ldt's performance in the first place.

This fixes some fallout from the CVE-2015-5157 fixes.

Signed-off-by: Andy Lutomirski 
Reviewed-by: Borislav Petkov 
Cc: Andrew Cooper 
Cc: Andy Lutomirski 
Cc: Boris Ostrovsky 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Jan Beulich 
Cc: Konrad Rzeszutek Wilk 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Sasha Levin 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Cc: security@kernel.org 
Cc: xen-devel 
Link: http://lkml.kernel.org/r/4c6978476782160600471bd865b318db34c7b628.1438291540.git.luto@kernel.org
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

x86_64, asm: Work around AMD SYSRET SS descriptor attribute issue

2015-04-27T00:57:38+00:00

AMD CPUs don't reinitialize the SS descriptor on SYSRET, so SYSRET with
SS == 0 results in an invalid usermode state in which SS is apparently
equal to __USER_DS but causes #SS if used.

Work around the issue by setting SS to __KERNEL_DS __switch_to, thus
ensuring that SYSRET never happens with SS set to NULL.

This was exposed by a recent vDSO cleanup.

Fixes: e7d6eefaaa44 x86/vdso32/syscall.S: Do not load __USER32_DS to %ss
Signed-off-by: Andy Lutomirski 
Cc: Peter Anvin 
Cc: Borislav Petkov 
Cc: Denys Vlasenko 
Cc: Brian Gerst 
Signed-off-by: Linus Torvalds

x86/asm/entry: Get rid of KERNEL_STACK_OFFSET

2015-03-24T18:42:38+00:00

PER_CPU_VAR(kernel_stack) was set up in a way where it points
five stack slots below the top of stack.

Presumably, it was done to avoid one "sub $5*8,%rsp"
in syscall/sysenter code paths, where iret frame needs to be
created by hand.

Ironically, none of them benefits from this optimization,
since all of them need to allocate additional data on stack
(struct pt_regs), so they still have to perform subtraction.

This patch eliminates KERNEL_STACK_OFFSET.

PER_CPU_VAR(kernel_stack) now points directly to top of stack.
pt_regs allocations are adjusted to allocate iret frame as well.
Hopefully we can merge it later with 32-bit specific
PER_CPU_VAR(cpu_current_top_of_stack) variable...

Net result in generated code is that constants in several insns
are changed.

This change is necessary for changing struct pt_regs creation
in SYSCALL64 code path from MOV to PUSH instructions.

Signed-off-by: Denys Vlasenko 
Acked-by: Borislav Petkov 
Acked-by: Andy Lutomirski 
Cc: Alexei Starovoitov 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Frederic Weisbecker 
Cc: H. Peter Anvin 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Steven Rostedt 
Cc: Will Drewry 
Link: http://lkml.kernel.org/r/1426785469-15125-2-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar

x86/asm/entry: Fix execve() and sigreturn() syscalls to always return via IRET

2015-03-23T07:52:46+00:00

Both the execve() and sigreturn() family of syscalls have the
ability to change registers in ways that may not be compatabile
with the syscall path they were called from.

In particular, SYSRET and SYSEXIT can't handle non-default %cs and %ss,
and some bits in eflags.

These syscalls have stubs that are hardcoded to jump to the IRET path,
and not return to the original syscall path.

The following commit:

   76f5df43cab5e76 ("Always allocate a complete "struct pt_regs" on the kernel stack")

recently changed this for some 32-bit compat syscalls, but introduced a bug where
execve from a 32-bit program to a 64-bit program would fail because it still returned
via SYSRETL. This caused Wine to fail when built for both 32-bit and 64-bit.

This patch sets TIF_NOTIFY_RESUME for execve() and sigreturn() so
that the IRET path is always taken on exit to userspace.

Signed-off-by: Brian Gerst 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Link: http://lkml.kernel.org/r/1426978461-32089-1-git-send-email-brgerst@gmail.com
[ Improved the changelog and comments. ]
Signed-off-by: Ingo Molnar

x86/asm/entry/64: Rename 'old_rsp' to 'rsp_scratch'

2015-03-17T15:01:42+00:00

Make clear that the usage of PER_CPU(old_rsp) is purely temporary,
by renaming it to 'rsp_scratch'.

Cc: Alexei Starovoitov 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Denys Vlasenko 
Cc: Frederic Weisbecker 
Cc: H. Peter Anvin 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Steven Rostedt 
Cc: Will Drewry 
Signed-off-by: Ingo Molnar

x86/asm/entry/64: Remove thread_struct::usersp

2015-03-17T15:01:41+00:00

Nothing uses thread_struct::usersp anymore, so remove it.

Originally-from: Denys Vlasenko 
Tested-by: Borislav Petkov 
Acked-by: Borislav Petkov 
Cc: Alexei Starovoitov 
Cc: Andy Lutomirski 
Cc: Denys Vlasenko 
Cc: Frederic Weisbecker 
Cc: H. Peter Anvin 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Steven Rostedt 
Cc: Will Drewry 
Signed-off-by: Ingo Molnar

x86/asm/entry/64: Simplify 'old_rsp' usage

2015-03-17T15:01:41+00:00

Remove all manipulations of PER_CPU(old_rsp) in C code:

 - it is not used on SYSRET return anymore, and system entries
   are atomic, so updating it from the fork and context switch
   paths is pointless.

 - Tweak a few related comments as well: we no longer have a
   "partial stack frame" on entry, ever.

Based on (split out of) patch from Denys Vlasenko.

Originally-from: Denys Vlasenko 
Tested-by: Borislav Petkov 
Acked-by: Borislav Petkov 
Cc: Alexei Starovoitov 
Cc: Andy Lutomirski 
Cc: Denys Vlasenko 
Cc: Frederic Weisbecker 
Cc: H. Peter Anvin 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Steven Rostedt 
Cc: Will Drewry 
Link: http://lkml.kernel.org/r/1426599779-8010-2-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar

x86/asm/entry/64: Save user RSP in pt_regs->sp on SYSCALL64 fastpath

2015-03-10T12:56:10+00:00

Prepare for the removal of 'usersp', by simplifying PER_CPU(old_rsp) usage:

  - use it only as temp storage

  - store the userspace stack pointer immediately in pt_regs->sp
    on syscall entry, instead of using it later, on syscall exit.

  - change C code to use pt_regs->sp only, instead of PER_CPU(old_rsp)
    and task->thread.usersp.

FIXUP/RESTORE_TOP_OF_STACK are simplified as well.

Signed-off-by: Denys Vlasenko 
Cc: Alexei Starovoitov 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Frederic Weisbecker 
Cc: H. Peter Anvin 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Steven Rostedt 
Cc: Will Drewry 
Link: http://lkml.kernel.org/r/1425926364-9526-4-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar