[tip: core/entry] ARM: Snapshot thread flags

[tip-bot2 for Mark Rutland]

The following commit has been merged into the core/entry branch of tip:

Commit-ID:     050e22bfc4f450d342dbb7eaea470858ad567bce
Gitweb:        https://git.kernel.org/tip/050e22bfc4f450d342dbb7eaea470858ad567bce
Author:        Mark Rutland <mark.rutland@xxxxxxx>
AuthorDate:    Mon, 29 Nov 2021 13:06:47 
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Wed, 01 Dec 2021 00:06:43 +01:00

ARM: Snapshot thread flags

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>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20211129130653.2037928-6-mark.rutland@xxxxxxx

---
 arch/arm/kernel/signal.c | 2 +-
 arch/arm/mm/alignment.c  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index a41e27a..c532a60 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -631,7 +631,7 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 			}
 		}
 		local_irq_disable();
-		thread_flags = current_thread_info()->flags;
+		thread_flags = read_thread_flags();
 	} while (thread_flags & _TIF_WORK_MASK);
 	return 0;
 }
diff --git a/arch/arm/mm/alignment.c b/arch/arm/mm/alignment.c
index ea81e89..adbb381 100644
--- a/arch/arm/mm/alignment.c
+++ b/arch/arm/mm/alignment.c
@@ -990,7 +990,7 @@ do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 		 * there is no work pending for this thread.
 		 */
 		raw_local_irq_disable();
-		if (!(current_thread_info()->flags & _TIF_WORK_MASK))
+		if (!(read_thread_flags() & _TIF_WORK_MASK))
 			set_cr(cr_no_alignment);
 	}