Merge branch 'per_signal_struct_coredumps-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull per signal_struct coredumps from Eric Biederman:
 "Current coredumps are mixed up with the exit code, the signal handling
  code, and the ptrace code making coredumps much more complicated than
  necessary and difficult to follow.

  This series of changes starts with ptrace_stop and cleans it up,
  making it easier to follow what is happening in ptrace_stop. Then
  cleans up the exec interactions with coredumps. Then cleans up the
  coredump interactions with exit. Finally the coredump interactions
  with the signal handling code is cleaned up.

  The first and last changes are bug fixes for minor bugs.

  I believe the fact that vfork followed by execve can kill the process
  the called vfork if exec fails is sufficient justification to change
  the userspace visible behavior.

  In previous discussions some of these changes were organized
  differently and individually appeared to make the code base worse. As
  currently written I believe they all stand on their own as cleanups
  and bug fixes.

  Which means that even if the worst should happen and the last change
  needs to be reverted for some unimaginable reason, the code base will
  still be improved.

  If the worst does not happen there are a more cleanups that can be
  made. Signals that generate coredumps can easily become eligible for
  short circuit delivery in complete_signal. The entire rendezvous for
  generating a coredump can move into get_signal. The function
  force_sig_info_to_task be written in a way that does not modify the
  signal handling state of the target task (because coredumps are
  eligible for short circuit delivery). Many of these future cleanups
  can be done another way but nothing so cleanly as if coredumps become
  per signal_struct"

* 'per_signal_struct_coredumps-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  coredump: Limit coredumps to a single thread group
  coredump:  Don't perform any cleanups before dumping core
  exit: Factor coredump_exit_mm out of exit_mm
  exec: Check for a pending fatal signal instead of core_state
  ptrace: Remove the unnecessary arguments from arch_ptrace_stop
  signal: Remove the bogus sigkill_pending in ptrace_stop

4 files changed, 23 insertions, 26 deletions

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 8f3131477ec6..f7326c8704bb 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -454,17 +454,6 @@ struct vm_area_struct {
 	struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
 } __randomize_layout;
 
-struct core_thread {
-	struct task_struct *task;
-	struct core_thread *next;
-};
-
-struct core_state {
-	atomic_t nr_threads;
-	struct core_thread dumper;
-	struct completion startup;
-};
-
 struct kioctx_table;
 struct mm_struct {
 	struct {
@@ -585,8 +574,6 @@ struct mm_struct {
 
 		unsigned long flags; /* Must use atomic bitops to access */
 
-		struct core_state *core_state; /* coredumping support */
-
 #ifdef CONFIG_AIO
 		spinlock_t			ioctx_lock;
 		struct kioctx_table __rcu	*ioctx_table;
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index b5ebf6c01292..8aee2945ff08 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -362,29 +362,25 @@ static inline void user_single_step_report(struct pt_regs *regs)
 #ifndef arch_ptrace_stop_needed
 /**
  * arch_ptrace_stop_needed - Decide whether arch_ptrace_stop() should be called
- * @code:	current->exit_code value ptrace will stop with
- * @info:	siginfo_t pointer (or %NULL) for signal ptrace will stop with
  *
  * This is called with the siglock held, to decide whether or not it's
- * necessary to release the siglock and call arch_ptrace_stop() with the
- * same @code and @info arguments.  It can be defined to a constant if
- * arch_ptrace_stop() is never required, or always is.  On machines where
- * this makes sense, it should be defined to a quick test to optimize out
- * calling arch_ptrace_stop() when it would be superfluous.  For example,
- * if the thread has not been back to user mode since the last stop, the
- * thread state might indicate that nothing needs to be done.
+ * necessary to release the siglock and call arch_ptrace_stop().  It can be
+ * defined to a constant if arch_ptrace_stop() is never required, or always
+ * is.  On machines where this makes sense, it should be defined to a quick
+ * test to optimize out calling arch_ptrace_stop() when it would be
+ * superfluous.  For example, if the thread has not been back to user mode
+ * since the last stop, the thread state might indicate that nothing needs
+ * to be done.
  *
  * This is guaranteed to be invoked once before a task stops for ptrace and
  * may include arch-specific operations necessary prior to a ptrace stop.
  */
-#define arch_ptrace_stop_needed(code, info)	(0)
+#define arch_ptrace_stop_needed()	(0)
 #endif
 
 #ifndef arch_ptrace_stop
 /**
  * arch_ptrace_stop - Do machine-specific work before stopping for ptrace
- * @code:	current->exit_code value ptrace will stop with
- * @info:	siginfo_t pointer (or %NULL) for signal ptrace will stop with
  *
  * This is called with no locks held when arch_ptrace_stop_needed() has
  * just returned nonzero.  It is allowed to block, e.g. for user memory
@@ -394,7 +390,7 @@ static inline void user_single_step_report(struct pt_regs *regs)
  * we only do it when the arch requires it for this particular stop, as
  * indicated by arch_ptrace_stop_needed().
  */
-#define arch_ptrace_stop(code, info)		do { } while (0)
+#define arch_ptrace_stop()		do { } while (0)
 #endif
 
 #ifndef current_pt_regs
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6f6f8f340a0f..78c351e35fec 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1661,6 +1661,7 @@ extern struct pid *cad_pid;
 #define PF_VCPU			0x00000001	/* I'm a virtual CPU */
 #define PF_IDLE			0x00000002	/* I am an IDLE thread */
 #define PF_EXITING		0x00000004	/* Getting shut down */
+#define PF_POSTCOREDUMP		0x00000008	/* Coredumps should ignore this task */
 #define PF_IO_WORKER		0x00000010	/* Task is an IO worker */
 #define PF_WQ_WORKER		0x00000020	/* I'm a workqueue worker */
 #define PF_FORKNOEXEC		0x00000040	/* Forked but didn't exec */
diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index e5f4ce622ee6..a8fe2a593a3a 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -72,6 +72,17 @@ struct multiprocess_signals {
 	struct hlist_node node;
 };
 
+struct core_thread {
+	struct task_struct *task;
+	struct core_thread *next;
+};
+
+struct core_state {
+	atomic_t nr_threads;
+	struct core_thread dumper;
+	struct completion startup;
+};
+
 /*
  * NOTE! "signal_struct" does not have its own
  * locking, because a shared signal_struct always
@@ -110,6 +121,8 @@ struct signal_struct {
 	int			group_stop_count;
 	unsigned int		flags; /* see SIGNAL_* flags below */
 
+	struct core_state *core_state; /* coredumping support */
+
 	/*
 	 * PR_SET_CHILD_SUBREAPER marks a process, like a service
 	 * manager, to re-parent orphan (double-forking) child processes