From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Sat, 15 Jul 2023 03:19:25 +0000 (-0700)
Subject: Merge tag 'x86_urgent_for_6.5_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git... 
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=b6e6cc1f78c772e952495b7416c9ac9029f9390c;p=linux.git

Merge tag 'x86_urgent_for_6.5_rc2' of git://git./linux/kernel/git/tip/tip

Pull x86 CFI fixes from Peter Zijlstra:
 "Fix kCFI/FineIBT weaknesses

  The primary bug Alyssa noticed was that with FineIBT enabled function
  prologues have a spurious ENDBR instruction:

    __cfi_foo:
	endbr64
	subl	$hash, %r10d
	jz	1f
	ud2
	nop
    1:
    foo:
	endbr64 <--- *sadface*

  This means that any indirect call that fails to target the __cfi
  symbol and instead targets (the regular old) foo+0, will succeed due
  to that second ENDBR.

  Fixing this led to the discovery of a single indirect call that was
  still doing this: ret_from_fork(). Since that's an assembly stub the
  compiler would not generate the proper kCFI indirect call magic and it
  would not get patched.

  Brian came up with the most comprehensive fix -- convert the thing to
  C with only a very thin asm wrapper. This ensures the kernel thread
  boostrap is a proper kCFI call.

  While discussing all this, Kees noted that kCFI hashes could/should be
  poisoned to seal all functions whose address is never taken, further
  limiting the valid kCFI targets -- much like we already do for IBT.

  So what was a 'simple' observation and fix cascaded into a bunch of
  inter-related CFI infrastructure fixes"

* tag 'x86_urgent_for_6.5_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/cfi: Only define poison_cfi() if CONFIG_X86_KERNEL_IBT=y
  x86/fineibt: Poison ENDBR at +0
  x86: Rewrite ret_from_fork() in C
  x86/32: Remove schedule_tail_wrapper()
  x86/cfi: Extend ENDBR sealing to kCFI
  x86/alternative: Rename apply_ibt_endbr()
  x86/cfi: Extend {JMP,CAKK}_NOSPEC comment
---

b6e6cc1f78c772e952495b7416c9ac9029f9390c