tree 9795b983ab97f90fcf9a12df1eb1ca065ddae0a5
parent 82f2b0b97b36ee3fcddf0f0780a9a0825d52fec3
parent 073fdbe02c69c43fb7c0d547ec265c7747d4a646
author Linus Torvalds <torvalds@linux-foundation.org> 1747009026 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1747009026 -0700
mergetag object 073fdbe02c69c43fb7c0d547ec265c7747d4a646
 type commit
 tag ibti-hisory-for-linus-2025-05-06
 tagger Dave Hansen <dave.hansen@linux.intel.com> 1746544780 -0700
 
  * Mitigate Intra-mode Branch History Injection via classic BFP
    programs
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Merge tag 'ibti-hisory-for-linus-2025-05-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 IBTI mitigation from Dave Hansen:
 "Mitigate Intra-mode Branch History Injection via classic BFP programs

  This adds the branch history clearing mitigation to cBPF programs for
  x86. Intra-mode BHI attacks via cBPF a.k.a IBTI-History was reported
  by researchers at VUSec.

  For hardware that doesn't support BHI_DIS_S, the recommended
  mitigation is to run the short software sequence followed by the IBHF
  instruction after cBPF execution. On hardware that does support
  BHI_DIS_S, enable BHI_DIS_S and execute the IBHF after cBPF execution.

  The Indirect Branch History Fence (IBHF) is a new instruction that
  prevents indirect branch target predictions after the barrier from
  using branch history from before the barrier while BHI_DIS_S is
  enabled. On older systems this will map to a NOP. It is recommended to
  add this fence at the end of the cBPF program to support VM migration.
  This instruction is required on newer parts with BHI_NO to fully
  mitigate against these attacks.

  The current code disables the mitigation for anything running with the
  SYS_ADMIN capability bit set. The intention was not to waste time
  mitigating a process that has access to anything it wants anyway"

* tag 'ibti-hisory-for-linus-2025-05-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/bhi: Do not set BHI_DIS_S in 32-bit mode
  x86/bpf: Add IBHF call at end of classic BPF
  x86/bpf: Call branch history clearing sequence on exit