linux-kernel - [tip: core/entry] arm64: Snapshot thread flags

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Message-ID: <163831372148.11128.11692234489872445198.tip-bot2@tip-bot2>
Date:   Tue, 30 Nov 2021 23:08:41 -0000
From:   "tip-bot2 for Mark Rutland" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Mark Rutland <mark.rutland@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: core/entry] arm64: Snapshot thread flags

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

Commit-ID:     342b3808786518ced347f40b59bae68664e20007
Gitweb:        https://git.kernel.org/tip/342b3808786518ced347f40b59bae68664e20007
Author:        Mark Rutland <mark.rutland@....com>
AuthorDate:    Mon, 29 Nov 2021 13:06:48 
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Wed, 01 Dec 2021 00:06:44 +01:00

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@....com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Will Deacon <will@...nel.org>
Acked-by: Paul E. McKenney <paulmck@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Link: https://lore.kernel.org/r/20211129130653.2037928-7-mark.rutland@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 f7408ed..ef7fcef 100644
--- 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
--- 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
--- 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
--- 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);