Commit 58719daa authored Oct 16, 2024 by Sabyrzhan Tasbolatov Committed by Wen Zhiwei Nov 14, 2024

x86/traps: move kmsan check after instrumentation_begin

stable inclusion
from stable-v6.6.60
commit c117a980185ee3812612e7e453e356a6a4f05305
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IB44K1

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c117a980185ee3812612e7e453e356a6a4f05305

--------------------------------

[ Upstream commit 1db272864ff250b5e607283eaec819e1186c8e26 ]

During x86_64 kernel build with CONFIG_KMSAN, the objtool warns following:

  AR      built-in.a
  AR      vmlinux.a
  LD      vmlinux.o
vmlinux.o: warning: objtool: handle_bug+0x4: call to
    kmsan_unpoison_entry_regs() leaves .noinstr.text section
  OBJCOPY modules.builtin.modinfo
  GEN     modules.builtin
  MODPOST Module.symvers
  CC      .vmlinux.export.o

Moving kmsan_unpoison_entry_regs() _after_ instrumentation_begin() fixes
the warning.

There is decode_bug(regs->ip, &imm) is left before KMSAN unpoisoining, but
it has the return condition and if we include it after
instrumentation_begin() it results the warning "return with
instrumentation enabled", hence, I'm concerned that regs will not be KMSAN
unpoisoned if `ud_type == BUG_NONE` is true.

Link: https://lkml.kernel.org/r/20241016152407.3149001-1-snovitoll@gmail.com


Fixes: ba54d194 ("x86/traps: avoid KMSAN bugs originating from handle_bug()")
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Wen Zhiwei <wenzhiwei@kylinos.cn>

parent ee271ddd

arch/x86/kernel/traps.c

+6 −6

Original line number	Diff line number	Diff line
		@@ -264,12 +264,6 @@ static noinstr bool handle_bug(struct pt_regs *regs)
		int ud_type;
		u32 imm;

		/*
		* Normally @regs are unpoisoned by irqentry_enter(), but handle_bug()
		* is a rare case that uses @regs without passing them to
		* irqentry_enter().
		*/
		kmsan_unpoison_entry_regs(regs);
		ud_type = decode_bug(regs->ip, &imm);
		if (ud_type == BUG_NONE)
		return handled;
		@@ -278,6 +272,12 @@ static noinstr bool handle_bug(struct pt_regs *regs)
		* All lies, just get the WARN/BUG out.
		*/
		instrumentation_begin();
		/*
		* Normally @regs are unpoisoned by irqentry_enter(), but handle_bug()
		* is a rare case that uses @regs without passing them to
		* irqentry_enter().
		*/
		kmsan_unpoison_entry_regs(regs);
		/*
		* Since we're emulating a CALL with exceptions, restore the interrupt
		* state to what it was at the exception site.