[PATCH v4 05/10] arm: snapshot thread flags

From: Mark Rutland
Date: Tue Aug 03 2021 - 05:55:54 EST


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>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
---
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 a3a38d0a4c85..40c1178bd8c2 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -674,7 +674,7 @@ 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 ea81e89e7740..adbb3817d0be 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);
}

--
2.11.0