Commit 342b3808 authored by Mark Rutland's avatar Mark Rutland Committed by Thomas Gleixner
Browse files

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: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarWill Deacon <will@kernel.org>
Acked-by: default avatarPaul 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
parent 050e22bf

arch/arm64/kernel/entry-common.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

}

arch/arm64/kernel/ptrace.c

+2 −2
Original line number Diff line number Diff line
@@ -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);

arch/arm64/kernel/signal.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

}

arch/arm64/kernel/syscall.c

+2 −2
Original line number Diff line number Diff line
@@ -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);