linux-stable.git/arch/x86/kernel/process.c, branch linux-5.14.y

Revert "x86: Fix get_wchan() to support the ORC unwinder"

2021-11-18T13:01:34+00:00

This reverts commit f270511247a5b6257b84db17883e0b1189bf5e16 which is
commit bc9bbb81730ea667c31c5b284f95ee312bab466f upstream.

It has been reported to be causing problems, and is being reworked
upstream and has been dropped from the current 5.15.y stable queue until
it gets resolved.

Reported-by: Chris Rankin 
Reported-by: Thorsten Leemhuis 
Link: https://lore.kernel.org/r/ed000478-2a60-0066-c337-a04bffc112b1@leemhuis.info
Cc: Qi Zheng 
Cc: Stephen Rothwell 
Cc: Peter Zijlstra (Intel) 
Cc: Kees Cook 
Cc: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

Revert "sched: Add wrapper for get_wchan() to keep task blocked"

2021-11-18T13:01:34+00:00

This reverts commit e9ede14c116f1a6246eee89d320d60a90a86b5d5 which is
commit 42a20f86dc19f9282d974df0ba4d226c865ab9dd upstream.

It has been reported to be causing problems, and is being reworked
upstream and has been dropped from the current 5.15.y stable queue until
it gets resolved.

Reported-by: Chris Rankin 
Reported-by: Thorsten Leemhuis 
Link: https://lore.kernel.org/r/ed000478-2a60-0066-c337-a04bffc112b1@leemhuis.info
Cc: Stephen Rothwell 
Cc: Peter Zijlstra (Intel) 
Cc: Kees Cook 
Cc: Geert Uytterhoeven 
Cc: Russell King (Oracle) 
Cc: Mark Rutland 
Cc: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

Revert "x86: Fix __get_wchan() for !STACKTRACE"

2021-11-18T13:01:34+00:00

This reverts commit e1ff40b6194f09c1dd0f45b94fdf30c0374b5823 which is
commit 5d1ceb3969b6b2e47e2df6d17790a7c5a20fcbb4 upstream.

It has been reported to be causing problems, and is being reworked
upstream and has been dropped from the current 5.15.y stable queue until
it gets resolved.

Reported-by: Chris Rankin 
Reported-by: Thorsten Leemhuis 
Link: https://lore.kernel.org/r/ed000478-2a60-0066-c337-a04bffc112b1@leemhuis.info
Cc: Stephen Rothwell 
Cc: Peter Zijlstra (Intel) 
Cc: Kees Cook 
Cc: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

x86: Fix __get_wchan() for !STACKTRACE

2021-11-17T10:04:16+00:00

[ Upstream commit 5d1ceb3969b6b2e47e2df6d17790a7c5a20fcbb4 ]

Use asm/unwind.h to implement wchan, since we cannot always rely on
STACKTRACE=y.

Fixes: bc9bbb81730e ("x86: Fix get_wchan() to support the ORC unwinder")
Reported-by: Stephen Rothwell 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Kees Cook 
Link: https://lkml.kernel.org/r/20211022152104.137058575@infradead.org
Signed-off-by: Sasha Levin

sched: Add wrapper for get_wchan() to keep task blocked

2021-11-17T10:04:16+00:00

[ Upstream commit 42a20f86dc19f9282d974df0ba4d226c865ab9dd ]

Having a stable wchan means the process must be blocked and for it to
stay that way while performing stack unwinding.

Suggested-by: Peter Zijlstra 
Signed-off-by: Kees Cook 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Geert Uytterhoeven 
Acked-by: Russell King (Oracle)  [arm]
Tested-by: Mark Rutland  [arm64]
Link: https://lkml.kernel.org/r/20211008111626.332092234@infradead.org
Signed-off-by: Sasha Levin

x86: Fix get_wchan() to support the ORC unwinder

2021-11-17T10:04:07+00:00

[ Upstream commit bc9bbb81730ea667c31c5b284f95ee312bab466f ]

Currently, the kernel CONFIG_UNWINDER_ORC option is enabled by default
on x86, but the implementation of get_wchan() is still based on the frame
pointer unwinder, so the /proc//wchan usually returned 0 regardless
of whether the task  is running.

Reimplement get_wchan() by calling stack_trace_save_tsk(), which is
adapted to the ORC and frame pointer unwinders.

Fixes: ee9f8fce9964 ("x86/unwind: Add the ORC unwinder")
Signed-off-by: Qi Zheng 
Signed-off-by: Kees Cook 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20211008111626.271115116@infradead.org
Signed-off-by: Sasha Levin

x86/iopl: Fake iopl(3) CLI/STI usage

2021-11-17T10:03:27+00:00

commit b968e84b509da593c50dc3db679e1d33de701f78 upstream.

Since commit c8137ace5638 ("x86/iopl: Restrict iopl() permission
scope") it's possible to emulate iopl(3) using ioperm(), except for
the CLI/STI usage.

Userspace CLI/STI usage is very dubious (read broken), since any
exception taken during that window can lead to rescheduling anyway (or
worse). The IOPL(2) manpage even states that usage of CLI/STI is highly
discouraged and might even crash the system.

Of course, that won't stop people and HP has the dubious honour of
being the first vendor to be found using this in their hp-health
package.

In order to enable this 'software' to still 'work', have the #GP treat
the CLI/STI instructions as NOPs when iopl(3). Warn the user that
their program is doing dubious things.

Fixes: a24ca9976843 ("x86/iopl: Remove legacy IOPL option")
Reported-by: Ondrej Zary 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Thomas Gleixner 
Cc: stable@kernel.org # v5.5+
Link: https://lkml.kernel.org/r/20210918090641.GD5106@worktop.programming.kicks-ass.net
Signed-off-by: Greg Kroah-Hartman

Merge tag 'x86-fpu-2021-07-07' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2021-07-07T18:12:01+00:00

Pull x86 fpu updates from Thomas Gleixner:
 "Fixes and improvements for FPU handling on x86:

   - Prevent sigaltstack out of bounds writes.

     The kernel unconditionally writes the FPU state to the alternate
     stack without checking whether the stack is large enough to
     accomodate it.

     Check the alternate stack size before doing so and in case it's too
     small force a SIGSEGV instead of silently corrupting user space
     data.

   - MINSIGSTKZ and SIGSTKSZ are constants in signal.h and have never
     been updated despite the fact that the FPU state which is stored on
     the signal stack has grown over time which causes trouble in the
     field when AVX512 is available on a CPU. The kernel does not expose
     the minimum requirements for the alternate stack size depending on
     the available and enabled CPU features.

     ARM already added an aux vector AT_MINSIGSTKSZ for the same reason.
     Add it to x86 as well.

   - A major cleanup of the x86 FPU code. The recent discoveries of
     XSTATE related issues unearthed quite some inconsistencies,
     duplicated code and other issues.

     The fine granular overhaul addresses this, makes the code more
     robust and maintainable, which allows to integrate upcoming XSTATE
     related features in sane ways"

* tag 'x86-fpu-2021-07-07' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (74 commits)
  x86/fpu/xstate: Clear xstate header in copy_xstate_to_uabi_buf() again
  x86/fpu/signal: Let xrstor handle the features to init
  x86/fpu/signal: Handle #PF in the direct restore path
  x86/fpu: Return proper error codes from user access functions
  x86/fpu/signal: Split out the direct restore code
  x86/fpu/signal: Sanitize copy_user_to_fpregs_zeroing()
  x86/fpu/signal: Sanitize the xstate check on sigframe
  x86/fpu/signal: Remove the legacy alignment check
  x86/fpu/signal: Move initial checks into fpu__restore_sig()
  x86/fpu: Mark init_fpstate __ro_after_init
  x86/pkru: Remove xstate fiddling from write_pkru()
  x86/fpu: Don't store PKRU in xstate in fpu_reset_fpstate()
  x86/fpu: Remove PKRU handling from switch_fpu_finish()
  x86/fpu: Mask PKRU from kernel XRSTOR[S] operations
  x86/fpu: Hook up PKRU into ptrace()
  x86/fpu: Add PKRU storage outside of task XSAVE buffer
  x86/fpu: Dont restore PKRU in fpregs_restore_userspace()
  x86/fpu: Rename xfeatures_mask_user() to xfeatures_mask_uabi()
  x86/fpu: Move FXSAVE_LEAK quirk info __copy_kernel_to_fpregs()
  x86/fpu: Rename __fpregs_load_activate() to fpregs_restore_userregs()
  ...

x86/fpu: Add PKRU storage outside of task XSAVE buffer

2021-06-23T17:37:45+00:00

PKRU is currently partly XSAVE-managed and partly not. It has space
in the task XSAVE buffer and is context-switched by XSAVE/XRSTOR.
However, it is switched more eagerly than FPU because there may be a
need for PKRU to be up-to-date for things like copy_to/from_user() since
PKRU affects user-permission memory accesses, not just accesses from
userspace itself.

This leaves PKRU in a very odd position. XSAVE brings very little value
to the table for how Linux uses PKRU except for signal related XSTATE
handling.

Prepare to move PKRU away from being XSAVE-managed. Allocate space in
the thread_struct for it and save/restore it in the context-switch path
separately from the XSAVE-managed features. task->thread_struct.pkru
is only valid when the task is scheduled out. For the current task the
authoritative source is the hardware, i.e. it has to be retrieved via
rdpkru().

Leave the XSAVE code in place for now to ensure bisectability.

Signed-off-by: Dave Hansen 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Reviewed-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20210623121456.399107624@linutronix.de

x86/fpu: Clean up the fpu__clear() variants

2021-06-23T17:23:07+00:00

fpu__clear() currently resets both register state and kernel XSAVE buffer
state.  It has two modes: one for all state (supervisor and user) and
another for user state only.  fpu__clear_all() uses the "all state"
(user_only=0) mode, while a number of signal paths use the user_only=1
mode.

Make fpu__clear() work only for user state (user_only=1) and remove the
"all state" (user_only=0) code.  Rename it to match so it can be used by
the signal paths.

Replace the "all state" (user_only=0) fpu__clear() functionality.  Use the
TIF_NEED_FPU_LOAD functionality instead of making any actual hardware
registers changes in this path.

Instead of invoking fpu__initialize() just memcpy() init_fpstate into the
task's FPU state because that has already the correct format and in case of
PKRU also contains the default PKRU value. Move the actual PKRU write out
into flush_thread() where it belongs and where it will end up anyway when
PKRU and XSTATE have been untangled.

For bisectability a workaround is required which stores the PKRU value in
the xstate memory until PKRU is untangled from XSTATE for context
switching and return to user.

[ Dave Hansen: Polished changelog ]
[ tglx: Fixed the PKRU fallout ]

Signed-off-by: Andy Lutomirski 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20210623121455.922729522@linutronix.de