x86/split-lock: Avoid returning with interrupts enabled

stable inclusion
from stable-5.10.3
commit 84bcbb0779c6a062e51c84abaca356f79be1abeb
bugzilla: 46871

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

commit e14fd4ba upstream.

When a split lock is detected always make sure to disable interrupts
before returning from the trap handler.

The kernel exit code assumes that all exits run with interrupts
disabled, otherwise the SWAPGS sequence can race against interrupts and
cause recursing page faults and later panics.

The problem will only happen on CPUs with split lock disable
functionality, so Icelake Server, Tiger Lake, Snow Ridge, Jacobsville.

Fixes: ca4c6a98 ("x86/traps: Make interrupt enable/disable symmetric in C code")
Fixes: bce9b042 ("x86/traps: Disable interrupts in exc_aligment_check()") # v5.8+
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>

arch/x86/kernel/traps.c

@@ -299,11 +299,12 @@ DEFINE_IDTENTRY_ERRORCODE(exc_alignment_check)
 	local_irq_enable();
 
 	if (handle_user_split_lock(regs, error_code))
-		return;
+		goto out;
 
 	do_trap(X86_TRAP_AC, SIGBUS, "alignment check", regs,
 		error_code, BUS_ADRALN, NULL);
 
+out:
 	local_irq_disable();
 }