linux-stable.git/arch/x86/kernel/alternative.c, branch linux-5.2.y

treewide: Add SPDX license identifier for missed files

2019-05-21T08:50:45+00:00

Add SPDX license identifiers to all files which:

 - Have no license information of any form

 - Have EXPORT_.*_SYMBOL_GPL inside which was used in the
   initial scan/conversion to ignore the file

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

  GPL-2.0-only

Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

x86/alternatives: Add comment about module removal races

2019-04-30T10:38:01+00:00

Add a comment to clarify that users of text_poke() must ensure that
no races with module removal take place.

Signed-off-by: Nadav Amit 
Signed-off-by: Rick Edgecombe 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Dave Hansen 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Masami Hiramatsu 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Link: https://lkml.kernel.org/r/20190426001143.4983-22-namit@vmware.com
Signed-off-by: Ingo Molnar

x86/alternatives: Remove the return value of text_poke_*()

2019-04-30T10:37:56+00:00

The return value of text_poke_early() and text_poke_bp() is useless.
Remove it.

Signed-off-by: Nadav Amit 
Signed-off-by: Rick Edgecombe 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Dave Hansen 
Cc: H. Peter Anvin 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Masami Hiramatsu 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Link: https://lkml.kernel.org/r/20190426001143.4983-14-namit@vmware.com
Signed-off-by: Ingo Molnar

x86/modules: Avoid breaking W^X while loading modules

2019-04-30T10:37:55+00:00

When modules and BPF filters are loaded, there is a time window in
which some memory is both writable and executable. An attacker that has
already found another vulnerability (e.g., a dangling pointer) might be
able to exploit this behavior to overwrite kernel code. Prevent having
writable executable PTEs in this stage.

In addition, avoiding having W+X mappings can also slightly simplify the
patching of modules code on initialization (e.g., by alternatives and
static-key), as would be done in the next patch. This was actually the
main motivation for this patch.

To avoid having W+X mappings, set them initially as RW (NX) and after
they are set as RO set them as X as well. Setting them as executable is
done as a separate step to avoid one core in which the old PTE is cached
(hence writable), and another which sees the updated PTE (executable),
which would break the W^X protection.

Suggested-by: Thomas Gleixner 
Suggested-by: Andy Lutomirski 
Signed-off-by: Nadav Amit 
Signed-off-by: Rick Edgecombe 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Dave Hansen 
Cc: H. Peter Anvin 
Cc: Jessica Yu 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Masami Hiramatsu 
Cc: Rik van Riel 
Link: https://lkml.kernel.org/r/20190426001143.4983-12-namit@vmware.com
Signed-off-by: Ingo Molnar

x86/alternatives: Use temporary mm for text poking

2019-04-30T10:37:52+00:00

text_poke() can potentially compromise security as it sets temporary
PTEs in the fixmap. These PTEs might be used to rewrite the kernel code
from other cores accidentally or maliciously, if an attacker gains the
ability to write onto kernel memory.

Moreover, since remote TLBs are not flushed after the temporary PTEs are
removed, the time-window in which the code is writable is not limited if
the fixmap PTEs - maliciously or accidentally - are cached in the TLB.
To address these potential security hazards, use a temporary mm for
patching the code.

Finally, text_poke() is also not conservative enough when mapping pages,
as it always tries to map 2 pages, even when a single one is sufficient.
So try to be more conservative, and do not map more than needed.

Signed-off-by: Nadav Amit 
Signed-off-by: Rick Edgecombe 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Dave Hansen 
Cc: H. Peter Anvin 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Masami Hiramatsu 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Link: https://lkml.kernel.org/r/20190426001143.4983-8-namit@vmware.com
Signed-off-by: Ingo Molnar

x86/alternatives: Initialize temporary mm for patching

2019-04-30T10:37:52+00:00

To prevent improper use of the PTEs that are used for text patching, the
next patches will use a temporary mm struct. Initailize it by copying
the init mm.

The address that will be used for patching is taken from the lower area
that is usually used for the task memory. Doing so prevents the need to
frequently synchronize the temporary-mm (e.g., when BPF programs are
installed), since different PGDs are used for the task memory.

Finally, randomize the address of the PTEs to harden against exploits
that use these PTEs.

Suggested-by: Andy Lutomirski 
Tested-by: Masami Hiramatsu 
Signed-off-by: Nadav Amit 
Signed-off-by: Rick Edgecombe 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Masami Hiramatsu 
Cc: Borislav Petkov 
Cc: Dave Hansen 
Cc: H. Peter Anvin 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Cc: akpm@linux-foundation.org
Cc: ard.biesheuvel@linaro.org
Cc: deneen.t.dock@intel.com
Cc: kernel-hardening@lists.openwall.com
Cc: kristen@linux.intel.com
Cc: linux_dti@icloud.com
Cc: will.deacon@arm.com
Link: https://lkml.kernel.org/r/20190426232303.28381-8-nadav.amit@gmail.com
Signed-off-by: Ingo Molnar

x86/alternatives: Add text_poke_kgdb() to not assert the lock when debugging

2019-04-30T10:37:47+00:00

text_mutex is currently expected to be held before text_poke() is
called, but kgdb does not take the mutex, and instead *supposedly*
ensures the lock is not taken and will not be acquired by any other core
while text_poke() is running.

The reason for the "supposedly" comment is that it is not entirely clear
that this would be the case if gdb_do_roundup is zero.

Create two wrapper functions, text_poke() and text_poke_kgdb(), which do
or do not run the lockdep assertion respectively.

While we are at it, change the return code of text_poke() to something
meaningful. One day, callers might actually respect it and the existing
BUG_ON() when patching fails could be removed. For kgdb, the return
value can actually be used.

Suggested-by: Peter Zijlstra 
Signed-off-by: Nadav Amit 
Signed-off-by: Rick Edgecombe 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Masami Hiramatsu 
Acked-by: Jiri Kosina 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Dave Hansen 
Cc: H. Peter Anvin 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Fixes: 9222f606506c ("x86/alternatives: Lockdep-enforce text_mutex in text_poke*()")
Link: https://lkml.kernel.org/r/20190426001143.4983-2-namit@vmware.com
Signed-off-by: Ingo Molnar

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

2019-03-06T16:45:46+00:00

Pull x86 alternative instruction updates from Ingo Molnar:
 "Small RDTSCP opimization, enabled by the newly added ALTERNATIVE_3(),
  and other small improvements"

* 'x86-alternatives-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/TSC: Use RDTSCP
  x86/alternatives: Add an ALTERNATIVE_3() macro
  x86/alternatives: Print containing function
  x86/alternatives: Add macro comments

x86/kprobes: Prohibit probing on functions before kprobe_int3_handler()

2019-02-13T07:16:39+00:00

Prohibit probing on the functions called before kprobe_int3_handler()
in do_int3(). More specifically, ftrace_int3_handler(),
poke_int3_handler(), and ist_enter(). And since rcu_nmi_enter() is
called by ist_enter(), it also should be marked as NOKPROBE_SYMBOL.

Since those are handled before kprobe_int3_handler(), probing those
functions can cause a breakpoint recursion and crash the kernel.

Signed-off-by: Masami Hiramatsu 
Cc: Alexander Shishkin 
Cc: Andrea Righi 
Cc: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Linus Torvalds 
Cc: Mathieu Desnoyers 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/154998793571.31052.11301258949601150994.stgit@devbox
Signed-off-by: Ingo Molnar

x86/alternatives: Print containing function

2019-01-16T11:41:57+00:00

... in the "debug-alternative" output so that one can find her way
easier when staring at the vmlinux disassembly.

For example:

  apply_alternatives: feat: 3*32+18, old: (read_tsc+0x0/0x10 (ffffffff8101d1c0) len: 5), repl: (ffffffff824e6d33, len: 5)
  					   ^^^^^^^^^^^^^^^^^
  ffffffff8101d1c0: old_insn: 0f 31 90 90 90
  ffffffff824e6d33: rpl_insn: 0f ae e8 0f 31
  ffffffff8101d1c0: final_insn: 0f ae e8 0f 31

No functional changes.

Signed-off-by: Borislav Petkov 
Cc: Andy Lutomirski 
Cc: "H. Peter Anvin" 
Cc: Josh Poimboeuf 
Cc: Peter Zijlstra 
Cc: Tom Lendacky 
Cc: X86 ML 
Link: https://lkml.kernel.org/r/20181211222326.14581-3-bp@alien8.de