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authorLinus Torvalds <torvalds@linux-foundation.org>2022-06-03 16:13:25 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-06-03 16:13:25 -0700
commit67850b7bdcd2803e10d019f0da5673a92139b43a (patch)
tree3f8914ce44edd9b5dd3a55ca4fb47efe0a5a2552 /arch/um
parent1ec6574a3c0a22c130c08e8c36c825cb87d68f8e (diff)
parent31cae1eaae4fd65095ad6a3659db467bc3c2599e (diff)
downloadlinux-67850b7bdcd2803e10d019f0da5673a92139b43a.tar.bz2
Merge tag 'ptrace_stop-cleanup-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull ptrace_stop cleanups from Eric Biederman: "While looking at the ptrace problems with PREEMPT_RT and the problems Peter Zijlstra was encountering with ptrace in his freezer rewrite I identified some cleanups to ptrace_stop that make sense on their own and move make resolving the other problems much simpler. The biggest issue is the habit of the ptrace code to change task->__state from the tracer to suppress TASK_WAKEKILL from waking up the tracee. No other code in the kernel does that and it is straight forward to update signal_wake_up and friends to make that unnecessary. Peter's task freezer sets frozen tasks to a new state TASK_FROZEN and then it stores them by calling "wake_up_state(t, TASK_FROZEN)" relying on the fact that all stopped states except the special stop states can tolerate spurious wake up and recover their state. The state of stopped and traced tasked is changed to be stored in task->jobctl as well as in task->__state. This makes it possible for the freezer to recover tasks in these special states, as well as serving as a general cleanup. With a little more work in that direction I believe TASK_STOPPED can learn to tolerate spurious wake ups and become an ordinary stop state. The TASK_TRACED state has to remain a special state as the registers for a process are only reliably available when the process is stopped in the scheduler. Fundamentally ptrace needs acess to the saved register values of a task. There are bunch of semi-random ptrace related cleanups that were found while looking at these issues. One cleanup that deserves to be called out is from commit 57b6de08b5f6 ("ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs"). This makes a change that is technically user space visible, in the handling of what happens to a tracee when a tracer dies unexpectedly. According to our testing and our understanding of userspace nothing cares that spurious SIGTRAPs can be generated in that case" * tag 'ptrace_stop-cleanup-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: sched,signal,ptrace: Rework TASK_TRACED, TASK_STOPPED state ptrace: Always take siglock in ptrace_resume ptrace: Don't change __state ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs ptrace: Document that wait_task_inactive can't fail ptrace: Reimplement PTRACE_KILL by always sending SIGKILL signal: Use lockdep_assert_held instead of assert_spin_locked ptrace: Remove arch_ptrace_attach ptrace/xtensa: Replace PT_SINGLESTEP with TIF_SINGLESTEP ptrace/um: Replace PT_DTRACE with TIF_SINGLESTEP signal: Replace __group_send_sig_info with send_signal_locked signal: Rename send_signal send_signal_locked
Diffstat (limited to 'arch/um')
-rw-r--r--arch/um/include/asm/thread_info.h2
-rw-r--r--arch/um/kernel/exec.c2
-rw-r--r--arch/um/kernel/process.c2
-rw-r--r--arch/um/kernel/ptrace.c8
-rw-r--r--arch/um/kernel/signal.c4
5 files changed, 10 insertions, 8 deletions
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 181cc9aafb25..80b90b1276a1 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -336,7 +336,7 @@ 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));