linux-kernel - [PATCH] um: Re-evaluate thread flags repeatedly

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-Id: <20250704-uml-thread_flags-v1-1-0e293fd8d627@linutronix.de>
Date: Fri, 04 Jul 2025 14:34:47 +0200
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Richard Weinberger <richard@....at>, 
 Anton Ivanov <anton.ivanov@...bridgegreys.com>, 
 Johannes Berg <johannes@...solutions.net>
Cc: linux-um@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>, 
 Nam Cao <namcao@...utronix.de>
Subject: [PATCH] um: Re-evaluate thread flags repeatedly

The thread flags may change during their processing.
For example a task_work can queue a new signal to be sent.
This signal should be delivered before returning to usespace again.

Evaluate the flags repeatedly similar to other architectures.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Reviewed-by: Nam Cao <namcao@...utronix.de>
---
 arch/um/include/asm/thread_info.h |  4 ++++
 arch/um/kernel/process.c          | 20 ++++++++++++--------
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/arch/um/include/asm/thread_info.h b/arch/um/include/asm/thread_info.h
index f9ad06fcc991a2b10e2aa6059880b993e3d60a2d..eb9b3a6d99e84751a0b48ba516aaf25752e90873 100644
--- a/arch/um/include/asm/thread_info.h
+++ b/arch/um/include/asm/thread_info.h
@@ -50,7 +50,11 @@ struct thread_info {
 #define _TIF_NOTIFY_SIGNAL	(1 << TIF_NOTIFY_SIGNAL)
 #define _TIF_MEMDIE		(1 << TIF_MEMDIE)
 #define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)
+#define _TIF_NOTIFY_RESUME	(1 << TIF_NOTIFY_RESUME)
 #define _TIF_SECCOMP		(1 << TIF_SECCOMP)
 #define _TIF_SINGLESTEP		(1 << TIF_SINGLESTEP)
 
+#define _TIF_WORK_MASK		(_TIF_NEED_RESCHED | _TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL | \
+				 _TIF_NOTIFY_RESUME)
+
 #endif
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index 0cd6fad3d908d43e84ebc821676e05377ec641e9..1be644de9e41ecdb94d379760ee8790c1d0657c6 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -82,14 +82,18 @@ struct task_struct *__switch_to(struct task_struct *from, struct task_struct *to
 void interrupt_end(void)
 {
 	struct pt_regs *regs = &current->thread.regs;
-
-	if (need_resched())
-		schedule();
-	if (test_thread_flag(TIF_SIGPENDING) ||
-	    test_thread_flag(TIF_NOTIFY_SIGNAL))
-		do_signal(regs);
-	if (test_thread_flag(TIF_NOTIFY_RESUME))
-		resume_user_mode_work(regs);
+	unsigned long thread_flags;
+
+	thread_flags = read_thread_flags();
+	while (thread_flags & _TIF_WORK_MASK) {
+		if (thread_flags & _TIF_NEED_RESCHED)
+			schedule();
+		if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
+			do_signal(regs);
+		if (thread_flags & _TIF_NOTIFY_RESUME)
+			resume_user_mode_work(regs);
+		thread_flags = read_thread_flags();
+	}
 }
 
 int get_current_pid(void)

---
base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494
change-id: 20250703-uml-thread_flags-df184535b6c7

Best regards,
-- 
Thomas Weißschuh <thomas.weissschuh@...utronix.de>