arm64: 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@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20211129130653.2037928-7-mark.rutland@arm.com

diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index f7408ed..ef7fcef 100644 (file)
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -129,7 +129,7 @@ static __always_inline void prepare_exit_to_user_mode(struct pt_regs *regs)
 
        local_daif_mask();
 
-       flags = READ_ONCE(current_thread_info()->flags);
+       flags = read_thread_flags();
        if (unlikely(flags & _TIF_WORK_MASK))
                do_notify_resume(regs, flags);
 }

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 88a9034..33cac3d 100644 (file)
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -1839,7 +1839,7 @@ static void tracehook_report_syscall(struct pt_regs *regs,
 
 int syscall_trace_enter(struct pt_regs *regs)
 {
-       unsigned long flags = READ_ONCE(current_thread_info()->flags);
+       unsigned long flags = read_thread_flags();
 
        if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) {
                tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
@@ -1862,7 +1862,7 @@ int syscall_trace_enter(struct pt_regs *regs)
 
 void syscall_trace_exit(struct pt_regs *regs)
 {
-       unsigned long flags = READ_ONCE(current_thread_info()->flags);
+       unsigned long flags = read_thread_flags();
 
        audit_syscall_exit(regs);
 

diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 8f6372b..d8aaf4b 100644 (file)
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -948,7 +948,7 @@ void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags)
                }
 
                local_daif_mask();
-               thread_flags = READ_ONCE(current_thread_info()->flags);
+               thread_flags = read_thread_flags();
        } while (thread_flags & _TIF_WORK_MASK);
 }
 

diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index 50a0f1a..c938603 100644 (file)
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -81,7 +81,7 @@ void syscall_trace_exit(struct pt_regs *regs);
 static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
                           const syscall_fn_t syscall_table[])
 {
-       unsigned long flags = current_thread_info()->flags;
+       unsigned long flags = read_thread_flags();
 
        regs->orig_x0 = regs->regs[0];
        regs->syscallno = scno;
@@ -148,7 +148,7 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
         */
        if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) {
                local_daif_mask();
-               flags = current_thread_info()->flags;
+               flags = read_thread_flags();
                if (!has_syscall_work(flags) && !(flags & _TIF_SINGLESTEP))
                        return;
                local_daif_restore(DAIF_PROCCTX);