Patch "entry: Snapshot thread flags" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    entry: Snapshot thread flags

to the 5.15-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:
     entry-snapshot-thread-flags.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit d3c2defe16ba78ebd44a7249ef6b470a760fa119
Author: Mark Rutland <mark.rutland@xxxxxxx>
Date:   Mon Nov 29 13:06:44 2021 +0000

    entry: Snapshot thread flags
    
    [ Upstream commit 6ce895128b3bff738fe8d9dd74747a03e319e466 ]
    
    Some thread flags can be set remotely, and so even when IRQs are disabled,
    the flags can change under our feet. Generally this is unlikely to cause a
    problem in practice, but it is somewhat unsound, and KCSAN will
    legitimately warn that there is a data race.
    
    To avoid such issues, a snapshot of the flags has to be taken prior to
    using them. Some places already use READ_ONCE() for that, others do not.
    
    Convert them all to the new flag accessor helpers.
    
    Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
    Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
    Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20211129130653.2037928-3-mark.rutland@xxxxxxx
    Stable-dep-of: b41651405481 ("entry/rcu: Check TIF_RESCHED _after_ delayed RCU wake-up")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/linux/entry-kvm.h b/include/linux/entry-kvm.h
index 0d7865a0731ce..07c878d6e323e 100644
--- a/include/linux/entry-kvm.h
+++ b/include/linux/entry-kvm.h
@@ -75,7 +75,7 @@ static inline void xfer_to_guest_mode_prepare(void)
  */
 static inline bool __xfer_to_guest_mode_work_pending(void)
 {
-	unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
+	unsigned long ti_work = read_thread_flags();
 
 	return !!(ti_work & XFER_TO_GUEST_MODE_WORK);
 }
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index 998bdb7b8bf7f..3ce3a0a6c762e 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -187,7 +187,7 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
 		/* Check if any of the above work has queued a deferred wakeup */
 		tick_nohz_user_enter_prepare();
 
-		ti_work = READ_ONCE(current_thread_info()->flags);
+		ti_work = read_thread_flags();
 	}
 
 	/* Return the latest work state for arch_exit_to_user_mode() */
@@ -196,7 +196,7 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
 
 static void exit_to_user_mode_prepare(struct pt_regs *regs)
 {
-	unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
+	unsigned long ti_work = read_thread_flags();
 
 	lockdep_assert_irqs_disabled();
 
diff --git a/kernel/entry/kvm.c b/kernel/entry/kvm.c
index 49972ee99aff6..96d476e06c777 100644
--- a/kernel/entry/kvm.c
+++ b/kernel/entry/kvm.c
@@ -26,7 +26,7 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
 		if (ret)
 			return ret;
 
-		ti_work = READ_ONCE(current_thread_info()->flags);
+		ti_work = read_thread_flags();
 	} while (ti_work & XFER_TO_GUEST_MODE_WORK || need_resched());
 	return 0;
 }
@@ -43,7 +43,7 @@ int xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu)
 	 * disabled in the inner loop before going into guest mode. No need
 	 * to disable interrupts here.
 	 */
-	ti_work = READ_ONCE(current_thread_info()->flags);
+	ti_work = read_thread_flags();
 	if (!(ti_work & XFER_TO_GUEST_MODE_WORK))
 		return 0;