This is a note to let you know that I've just added the patch titled
x86/traps: move kmsan check after instrumentation_begin
to the 6.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-traps-move-kmsan-check-after-instrumentation_beg.patch
and it can be found in the queue-6.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 2831a9462bb651fdd49c33fc8be9e64c2dc7212a
Author: Sabyrzhan Tasbolatov <snovitoll@xxxxxxxxx>
Date: Wed Oct 16 20:24:07 2024 +0500
x86/traps: move kmsan check after instrumentation_begin
[ 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@xxxxxxxxx
Fixes: ba54d194f8da ("x86/traps: avoid KMSAN bugs originating from handle_bug()")
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@xxxxxxxxx>
Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 415881607c5df..29ec49209ae01 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -261,12 +261,6 @@ 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;
@@ -275,6 +269,12 @@ 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.
