linux.git/arch/x86/kernel/stacktrace.c, branch v5.6

x86/stacktrace: Prevent access_ok() warnings in arch_stack_walk_user()

2019-07-22T08:42:36+00:00

When arch_stack_walk_user() is called from atomic contexts, access_ok() can
trigger the following warning if compiled with CONFIG_DEBUG_ATOMIC_SLEEP=y.

Reproducer:

  // CONFIG_DEBUG_ATOMIC_SLEEP=y
  # cd /sys/kernel/debug/tracing
  # echo 1 > options/userstacktrace
  # echo 1 > events/irq/irq_handler_entry/enable

  WARNING: CPU: 0 PID: 2649 at arch/x86/kernel/stacktrace.c:103 arch_stack_walk_user+0x6e/0xf6
  CPU: 0 PID: 2649 Comm: bash Not tainted 5.3.0-rc1+ #99
  RIP: 0010:arch_stack_walk_user+0x6e/0xf6
  Call Trace:
   
   stack_trace_save_user+0x10a/0x16d
   trace_buffer_unlock_commit_regs+0x185/0x240
   trace_event_buffer_commit+0xec/0x330
   trace_event_raw_event_irq_handler_entry+0x159/0x1e0
   __handle_irq_event_percpu+0x22d/0x440
   handle_irq_event_percpu+0x70/0x100
   handle_irq_event+0x5a/0x8b
   handle_edge_irq+0x12f/0x3f0
   handle_irq+0x34/0x40
   do_IRQ+0xa6/0x1f0
   common_interrupt+0xf/0xf
   

Fix it by calling __range_not_ok() directly instead of access_ok() as
copy_from_user_nmi() does. This is fine here because the actual copy is
inside a pagefault disabled region.

Reported-by: Juri Lelli 
Signed-off-by: Eiichi Tsukata 
Signed-off-by: Thomas Gleixner 
Link: https://lkml.kernel.org/r/20190722083216.16192-2-devel@etsukata.com

x86/stacktrace: Prevent infinite loop in arch_stack_walk_user()

2019-07-11T06:22:03+00:00

arch_stack_walk_user() checks `if (fp == frame.next_fp)` to prevent a
infinite loop by self reference but it's not enogh for circular reference.

Once a lack of return address is found, there is no point to continue the
loop, so break out.

Fixes: 02b67518e2b1 ("tracing: add support for userspace stacktraces in tracing/iter_ctrl")
Signed-off-by: Eiichi Tsukata 
Signed-off-by: Thomas Gleixner 
Acked-by: Linus Torvalds 
Link: https://lkml.kernel.org/r/20190711023501.963-1-devel@etsukata.com

x86/stacktrace: Use common infrastructure

2019-04-29T10:37:57+00:00

Replace the stack_trace_save*() functions with the new arch_stack_walk()
interfaces.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Josh Poimboeuf 
Cc: Andy Lutomirski 
Cc: linux-arch@vger.kernel.org
Cc: Steven Rostedt 
Cc: Alexander Potapenko 
Cc: Alexey Dobriyan 
Cc: Andrew Morton 
Cc: Christoph Lameter 
Cc: Pekka Enberg 
Cc: linux-mm@kvack.org
Cc: David Rientjes 
Cc: Catalin Marinas 
Cc: Dmitry Vyukov 
Cc: Andrey Ryabinin 
Cc: kasan-dev@googlegroups.com
Cc: Mike Rapoport 
Cc: Akinobu Mita 
Cc: Christoph Hellwig 
Cc: iommu@lists.linux-foundation.org
Cc: Robin Murphy 
Cc: Marek Szyprowski 
Cc: Johannes Thumshirn 
Cc: David Sterba 
Cc: Chris Mason 
Cc: Josef Bacik 
Cc: linux-btrfs@vger.kernel.org
Cc: dm-devel@redhat.com
Cc: Mike Snitzer 
Cc: Alasdair Kergon 
Cc: Daniel Vetter 
Cc: intel-gfx@lists.freedesktop.org
Cc: Joonas Lahtinen 
Cc: Maarten Lankhorst 
Cc: dri-devel@lists.freedesktop.org
Cc: David Airlie 
Cc: Jani Nikula 
Cc: Rodrigo Vivi 
Cc: Tom Zanussi 
Cc: Miroslav Benes 
Link: https://lkml.kernel.org/r/20190425094803.816485461@linutronix.de

x86/stacktrace: Remove the pointless ULONG_MAX marker

2019-04-14T17:58:27+00:00

Terminating the last trace entry with ULONG_MAX is a completely pointless
exercise and none of the consumers can rely on it because it's
inconsistently implemented across architectures. In fact quite some of the
callers remove the entry and adjust stack_trace.nr_entries afterwards.

Signed-off-by: Thomas Gleixner 
Acked-by: Peter Zijlstra (Intel) 
Cc: Josh Poimboeuf 
Cc: Andy Lutomirski 
Cc: Steven Rostedt 
Cc: Alexander Potapenko 
Link: https://lkml.kernel.org/r/20190410103643.750954603@linutronix.de

Remove 'type' argument from access_ok() function

2019-01-04T02:57:57+00:00

Nobody has actually used the type (VERIFY_READ vs VERIFY_WRITE) argument
of the user address range verification function since we got rid of the
old racy i386-only code to walk page tables by hand.

It existed because the original 80386 would not honor the write protect
bit when in kernel mode, so you had to do COW by hand before doing any
user access.  But we haven't supported that in a long time, and these
days the 'type' argument is a purely historical artifact.

A discussion about extending 'user_access_begin()' to do the range
checking resulted this patch, because there is no way we're going to
move the old VERIFY_xyz interface to that model.  And it's best done at
the end of the merge window when I've done most of my merges, so let's
just get this done once and for all.

This patch was mostly done with a sed-script, with manual fix-ups for
the cases that weren't of the trivial 'access_ok(VERIFY_xyz' form.

There were a couple of notable cases:

 - csky still had the old "verify_area()" name as an alias.

 - the iter_iov code had magical hardcoded knowledge of the actual
   values of VERIFY_{READ,WRITE} (not that they mattered, since nothing
   really used it)

 - microblaze used the type argument for a debug printout

but other than those oddities this should be a total no-op patch.

I tried to fix up all architectures, did fairly extensive grepping for
access_ok() uses, and the changes are trivial, but I may have missed
something.  Any missed conversion should be trivially fixable, though.

Signed-off-by: Linus Torvalds

x86/stacktrace: Do not fail for ORC with regs on stack

2018-06-21T14:34:56+00:00

save_stack_trace_reliable now returns "non reliable" when there are
kernel pt_regs on stack. This means an interrupt or exception happened
somewhere down the route. It is a problem for the frame pointer
unwinder, because the frame might not have been set up yet when the irq
happened, so the unwinder might fail to unwind from the interrupted
function.

With ORC, this is not a problem, as ORC has out-of-band data. We can
find ORC data even for the IP in the interrupted function and always
unwind one level up reliably.

So lift the check to apply only when CONFIG_FRAME_POINTER=y is enabled.

Signed-off-by: Jiri Slaby 
Acked-by: Josh Poimboeuf 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: https://lkml.kernel.org/lkml/20180518064713.26440-4-jslaby@suse.cz
Signed-off-by: Ingo Molnar

x86/stacktrace: Clarify the reliable success paths

2018-06-21T14:34:55+00:00

Make clear which path is for user tasks and for kthreads and idle
tasks. This will allow easier plug-in of the ORC unwinder in the next
patches.

Note that we added a check for unwind error to the top of the loop, so
that an error is returned also for user tasks (the 'goto success' would
skip the check after the loop otherwise).

Signed-off-by: Jiri Slaby 
Acked-by: Josh Poimboeuf 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: https://lkml.kernel.org/lkml/20180518064713.26440-3-jslaby@suse.cz
Signed-off-by: Ingo Molnar

x86/stacktrace: Remove STACKTRACE_DUMP_ONCE

2018-06-21T14:34:55+00:00

The stack unwinding can sometimes fail yet. Especially with the
generated debug info. So do not yell at users -- live patching (the only
user of this interface) will inform the user about the failure
gracefully.

And given this was the only user of the macro, remove the macro proper
too.

Signed-off-by: Jiri Slaby 
Acked-by: Josh Poimboeuf 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: https://lkml.kernel.org/lkml/20180518064713.26440-2-jslaby@suse.cz
Signed-off-by: Ingo Molnar

x86/stacktrace: Do not unwind after user regs

2018-06-21T14:34:55+00:00

Josh pointed out, that there is no way a frame can be after user regs.
So remove the last unwind and the check.

Signed-off-by: Jiri Slaby 
Acked-by: Josh Poimboeuf 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: https://lkml.kernel.org/lkml/20180518064713.26440-1-jslaby@suse.cz
Signed-off-by: Ingo Molnar

Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2018-01-04T00:41:07+00:00

Pull x86 page table isolation fixes from Thomas Gleixner:
 "A couple of urgent fixes for PTI:

   - Fix a PTE mismatch between user and kernel visible mapping of the
     cpu entry area (differs vs. the GLB bit) and causes a TLB mismatch
     MCE on older AMD K8 machines

   - Fix the misplaced CR3 switch in the SYSCALL compat entry code which
     causes access to unmapped kernel memory resulting in double faults.

   - Fix the section mismatch of the cpu_tss_rw percpu storage caused by
     using a different mechanism for declaration and definition.

   - Two fixes for dumpstack which help to decode entry stack issues
     better

   - Enable PTI by default in Kconfig. We should have done that earlier,
     but it slipped through the cracks.

   - Exclude AMD from the PTI enforcement. Not necessarily a fix, but if
     AMD is so confident that they are not affected, then we should not
     burden users with the overhead"

* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/process: Define cpu_tss_rw in same section as declaration
  x86/pti: Switch to kernel CR3 at early in entry_SYSCALL_compat()
  x86/dumpstack: Print registers for first stack frame
  x86/dumpstack: Fix partial register dumps
  x86/pti: Make sure the user/kernel PTEs match
  x86/cpu, x86/pti: Do not enable PTI on AMD processors
  x86/pti: Enable PTI by default