Messages in this thread Patch in this message | | | From | Mark Rutland <> | Subject | [PATCH v6 06/10] arm64: snapshot thread flags | Date | Fri, 22 Oct 2021 14:56:39 +0100 |
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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> Acked-by: Will Deacon <will@kernel.org> Acked-by: Paul E. McKenney <paulmck@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> --- arch/arm64/kernel/entry-common.c | 2 +- arch/arm64/kernel/ptrace.c | 4 ++-- arch/arm64/kernel/signal.c | 2 +- arch/arm64/kernel/syscall.c | 4 ++-- 4 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c index 32f9796c4ffe..83aef3dd6662 100644 --- a/arch/arm64/kernel/entry-common.c +++ b/arch/arm64/kernel/entry-common.c @@ -128,7 +128,7 @@ 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 e26196a33cf4..9dab4f127cfd 100644 --- 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 c287b9407f28..59f4c1b5d0cf 100644 --- 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 50a0f1a38e84..c938603b3ba0 100644 --- 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); -- 2.11.0
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