The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From c200e4bb44e80b343c09841e7caaaca0aac5e5fa Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" ebiederm@xmission.com Date: Tue, 26 Apr 2022 16:30:17 -0500 Subject: [PATCH] ptrace/um: Replace PT_DTRACE with TIF_SINGLESTEP

User mode linux is the last user of the PT_DTRACE flag. Using the flag to indicate single stepping is a little confusing and worse changing tsk->ptrace without locking could potentionally cause problems.

So use a thread info flag with a better name instead of flag in tsk->ptrace.

Remove the definition PT_DTRACE as uml is the last user.

Cc: stable@vger.kernel.org Acked-by: Johannes Berg johannes@sipsolutions.net Tested-by: Kees Cook keescook@chromium.org Reviewed-by: Oleg Nesterov oleg@redhat.com Link: https://lkml.kernel.org/r/20220505182645.497868-3-ebiederm@xmission.com Signed-off-by: "Eric W. Biederman" ebiederm@xmission.com

diff --git a/arch/um/include/asm/thread_info.h b/arch/um/include/asm/thread_info.h index 1395cbd7e340..c7b4b49826a2 100644 --- a/arch/um/include/asm/thread_info.h +++ b/arch/um/include/asm/thread_info.h @@ -60,6 +60,7 @@ static inline struct thread_info *current_thread_info(void) #define TIF_RESTORE_SIGMASK 7 #define TIF_NOTIFY_RESUME 8 #define TIF_SECCOMP 9 /* secure computing */ +#define TIF_SINGLESTEP 10 /* single stepping userspace */

#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE) #define _TIF_SIGPENDING (1 << TIF_SIGPENDING) @@ -68,5 +69,6 @@ static inline struct thread_info *current_thread_info(void) #define _TIF_MEMDIE (1 << TIF_MEMDIE) #define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT) #define _TIF_SECCOMP (1 << TIF_SECCOMP) +#define _TIF_SINGLESTEP (1 << TIF_SINGLESTEP)

#endif diff --git a/arch/um/kernel/exec.c b/arch/um/kernel/exec.c index c85e40c72779..58938d75871a 100644 --- a/arch/um/kernel/exec.c +++ b/arch/um/kernel/exec.c @@ -43,7 +43,7 @@ void start_thread(struct pt_regs *regs, unsigned long eip, unsigned long esp) { PT_REGS_IP(regs) = eip; PT_REGS_SP(regs) = esp; - current->ptrace &= ~PT_DTRACE; + clear_thread_flag(TIF_SINGLESTEP); #ifdef SUBARCH_EXECVE1 SUBARCH_EXECVE1(regs->regs); #endif diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c index 80504680be08..88c5c7844281 100644 --- a/arch/um/kernel/process.c +++ b/arch/um/kernel/process.c @@ -335,7 +335,7 @@ int singlestepping(void * t) { struct task_struct *task = t ? t : current;

- if (!(task->ptrace & PT_DTRACE)) + if (!test_thread_flag(TIF_SINGLESTEP)) return 0;

if (task->thread.singlestep_syscall) diff --git a/arch/um/kernel/ptrace.c b/arch/um/kernel/ptrace.c index bfaf6ab1ac03..5154b27de580 100644 --- a/arch/um/kernel/ptrace.c +++ b/arch/um/kernel/ptrace.c @@ -11,7 +11,7 @@

void user_enable_single_step(struct task_struct *child) { - child->ptrace |= PT_DTRACE; + set_tsk_thread_flag(child, TIF_SINGLESTEP); child->thread.singlestep_syscall = 0;

#ifdef SUBARCH_SET_SINGLESTEPPING @@ -21,7 +21,7 @@ void user_enable_single_step(struct task_struct *child)

void user_disable_single_step(struct task_struct *child) { - child->ptrace &= ~PT_DTRACE; + clear_tsk_thread_flag(child, TIF_SINGLESTEP); child->thread.singlestep_syscall = 0;

#ifdef SUBARCH_SET_SINGLESTEPPING @@ -120,7 +120,7 @@ static void send_sigtrap(struct uml_pt_regs *regs, int error_code) }

/* - * XXX Check PT_DTRACE vs TIF_SINGLESTEP for singlestepping check and + * XXX Check TIF_SINGLESTEP for singlestepping check and * PT_PTRACED vs TIF_SYSCALL_TRACE for syscall tracing check */ int syscall_trace_enter(struct pt_regs *regs) @@ -144,7 +144,7 @@ void syscall_trace_leave(struct pt_regs *regs) audit_syscall_exit(regs);

/* Fake a debug trap */ - if (ptraced & PT_DTRACE) + if (test_thread_flag(TIF_SINGLESTEP)) send_sigtrap(&regs->regs, 0);

if (!test_thread_flag(TIF_SYSCALL_TRACE)) diff --git a/arch/um/kernel/signal.c b/arch/um/kernel/signal.c index 88cd9b5c1b74..ae4658f576ab 100644 --- a/arch/um/kernel/signal.c +++ b/arch/um/kernel/signal.c @@ -53,7 +53,7 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs) unsigned long sp; int err;

- if ((current->ptrace & PT_DTRACE) && (current->ptrace & PT_PTRACED)) + if (test_thread_flag(TIF_SINGLESTEP) && (current->ptrace & PT_PTRACED)) singlestep = 1;

/* Did we come from a system call? */ @@ -128,7 +128,7 @@ void do_signal(struct pt_regs *regs) * on the host. The tracing thread will check this flag and * PTRACE_SYSCALL if necessary. */ - if (current->ptrace & PT_DTRACE) + if (test_thread_flag(TIF_SINGLESTEP)) current->thread.singlestep_syscall = is_syscall(PT_REGS_IP(&current->thread.regs));

diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h index 15b3d176b6b4..4c06f9f8ef3f 100644 --- a/include/linux/ptrace.h +++ b/include/linux/ptrace.h @@ -30,7 +30,6 @@ extern int ptrace_access_vm(struct task_struct *tsk, unsigned long addr,

#define PT_SEIZED 0x00010000 /* SEIZE used, enable new behavior */ #define PT_PTRACED 0x00000001 -#define PT_DTRACE 0x00000002 /* delayed trace (used on m68k, i386) */

#define PT_OPT_FLAG_SHIFT 3 /* PT_TRACE_* event enable flags */