1 files changed, 200 insertions, 45 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index d5f89f9ef29f..d041645d9d17 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -13,6 +13,7 @@
 #include <linux/sched.h>
 #include <linux/sched/mm.h>
 #include <linux/sched/coredump.h>
+#include <linux/sched/exec_state.h>
 #include <linux/sched/task.h>
 #include <linux/errno.h>
 #include <linux/mm.h>
@@ -36,6 +37,30 @@
 
 #include <asm/syscall.h>	/* for syscall_get_* */
 
+/**
+ * ptracer_access_allowed - may current peek/poke @tsk's address space?
+ * @tsk: tracee
+ *
+ * Per-access check used by ptrace_access_vm() and architecture-specific
+ * tag/register accessors.  Returns true iff current is the registered
+ * ptracer of @tsk and either @tsk is owner-dumpable or current holds
+ * CAP_SYS_PTRACE in @tsk's exec namespace.  Lighter than
+ * __ptrace_may_access(): it re-validates only dumpability and
+ * capability on every access, without re-running LSM hooks or
+ * cred_cap_issubset() checks performed at attach time.
+ */
+bool ptracer_access_allowed(struct task_struct *tsk)
+{
+	const struct task_exec_state *es;
+
+	guard(rcu)();
+	if (ptrace_parent(tsk) != current)
+		return false;
+	es = task_exec_state_rcu(tsk);
+	return READ_ONCE(es->dumpable) == TASK_DUMPABLE_OWNER ||
+	       ptracer_capable(tsk, es->user_ns);
+}
+
 /*
  * Access another process' address space via ptrace.
  * Source/target buffer must be kernel space,
@@ -45,21 +70,14 @@ int ptrace_access_vm(struct task_struct *tsk, unsigned long addr,
 		     void *buf, int len, unsigned int gup_flags)
 {
 	struct mm_struct *mm;
-	int ret;
+	int ret = 0;
 
 	mm = get_task_mm(tsk);
 	if (!mm)
 		return 0;
 
-	if (!tsk->ptrace ||
-	    (current != tsk->parent) ||
-	    ((get_dumpable(mm) != SUID_DUMP_USER) &&
-	     !ptracer_capable(tsk, mm->user_ns))) {
-		mmput(mm);
-		return 0;
-	}
-
-	ret = access_remote_vm(mm, addr, buf, len, gup_flags);
+	if (ptracer_access_allowed(tsk))
+		ret = access_remote_vm(mm, addr, buf, len, gup_flags);
 	mmput(mm);
 
 	return ret;
@@ -272,11 +290,21 @@ static bool ptrace_has_cap(struct user_namespace *ns, unsigned int mode)
 	return ns_capable(ns, CAP_SYS_PTRACE);
 }
 
+static bool task_still_dumpable(struct task_struct *task, unsigned int mode)
+{
+	const struct task_exec_state *exec_state;
+
+	guard(rcu)();
+	exec_state = task_exec_state_rcu(task);
+	if (READ_ONCE(exec_state->dumpable) == TASK_DUMPABLE_OWNER)
+		return true;
+	return ptrace_has_cap(exec_state->user_ns, mode);
+}
+
 /* Returns 0 on success, -errno on denial. */
 static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
 {
 	const struct cred *cred = current_cred(), *tcred;
-	struct mm_struct *mm;
 	kuid_t caller_uid;
 	kgid_t caller_gid;
 
@@ -337,11 +365,8 @@ ok:
 	 * Pairs with a write barrier in commit_creds().
 	 */
 	smp_rmb();
-	mm = task->mm;
-	if (mm &&
-	    ((get_dumpable(mm) != SUID_DUMP_USER) &&
-	     !ptrace_has_cap(mm->user_ns, mode)))
-	    return -EPERM;
+	if (!task_still_dumpable(task, mode))
+		return -EPERM;
 
 	return security_ptrace_access_check(task, mode);
 }
@@ -549,7 +574,8 @@ static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
 	if (!dead && thread_group_empty(p)) {
 		if (!same_thread_group(p->real_parent, tracer))
 			dead = do_notify_parent(p, p->exit_signal);
-		else if (ignoring_children(tracer->sighand)) {
+		else if (ignoring_children(tracer->sighand) ||
+			 p->signal->autoreap) {
 			__wake_up_parent(p, tracer);
 			dead = true;
 		}
@@ -793,9 +819,9 @@ static long ptrace_get_rseq_configuration(struct task_struct *task,
 					  unsigned long size, void __user *data)
 {
 	struct ptrace_rseq_configuration conf = {
-		.rseq_abi_pointer = (u64)(uintptr_t)task->rseq,
-		.rseq_abi_size = task->rseq_len,
-		.signature = task->rseq_sig,
+		.rseq_abi_pointer = (u64)(uintptr_t)task->rseq.usrptr,
+		.rseq_abi_size = task->rseq.len,
+		.signature = task->rseq.sig,
 		.flags = 0,
 	};
 
@@ -921,7 +947,6 @@ ptrace_get_syscall_info_entry(struct task_struct *child, struct pt_regs *regs,
 	unsigned long args[ARRAY_SIZE(info->entry.args)];
 	int i;
 
-	info->op = PTRACE_SYSCALL_INFO_ENTRY;
 	info->entry.nr = syscall_get_nr(child, regs);
 	syscall_get_arguments(child, regs, args);
 	for (i = 0; i < ARRAY_SIZE(args); i++)
@@ -943,10 +968,12 @@ ptrace_get_syscall_info_seccomp(struct task_struct *child, struct pt_regs *regs,
 	 * diverge significantly enough.
 	 */
 	ptrace_get_syscall_info_entry(child, regs, info);
-	info->op = PTRACE_SYSCALL_INFO_SECCOMP;
 	info->seccomp.ret_data = child->ptrace_message;
 
-	/* ret_data is the last field in struct ptrace_syscall_info.seccomp */
+	/*
+	 * ret_data is the last non-reserved field
+	 * in struct ptrace_syscall_info.seccomp
+	 */
 	return offsetofend(struct ptrace_syscall_info, seccomp.ret_data);
 }
 
@@ -954,7 +981,6 @@ static unsigned long
 ptrace_get_syscall_info_exit(struct task_struct *child, struct pt_regs *regs,
 			     struct ptrace_syscall_info *info)
 {
-	info->op = PTRACE_SYSCALL_INFO_EXIT;
 	info->exit.rval = syscall_get_error(child, regs);
 	info->exit.is_error = !!info->exit.rval;
 	if (!info->exit.is_error)
@@ -965,19 +991,8 @@ ptrace_get_syscall_info_exit(struct task_struct *child, struct pt_regs *regs,
 }
 
 static int
-ptrace_get_syscall_info(struct task_struct *child, unsigned long user_size,
-			void __user *datavp)
+ptrace_get_syscall_info_op(struct task_struct *child)
 {
-	struct pt_regs *regs = task_pt_regs(child);
-	struct ptrace_syscall_info info = {
-		.op = PTRACE_SYSCALL_INFO_NONE,
-		.arch = syscall_get_arch(child),
-		.instruction_pointer = instruction_pointer(regs),
-		.stack_pointer = user_stack_pointer(regs),
-	};
-	unsigned long actual_size = offsetof(struct ptrace_syscall_info, entry);
-	unsigned long write_size;
-
 	/*
 	 * This does not need lock_task_sighand() to access
 	 * child->last_siginfo because ptrace_freeze_traced()
@@ -988,24 +1003,160 @@ ptrace_get_syscall_info(struct task_struct *child, unsigned long user_size,
 	case SIGTRAP | 0x80:
 		switch (child->ptrace_message) {
 		case PTRACE_EVENTMSG_SYSCALL_ENTRY:
-			actual_size = ptrace_get_syscall_info_entry(child, regs,
-								    &info);
-			break;
+			return PTRACE_SYSCALL_INFO_ENTRY;
 		case PTRACE_EVENTMSG_SYSCALL_EXIT:
-			actual_size = ptrace_get_syscall_info_exit(child, regs,
-								   &info);
-			break;
+			return PTRACE_SYSCALL_INFO_EXIT;
+		default:
+			return PTRACE_SYSCALL_INFO_NONE;
 		}
-		break;
 	case SIGTRAP | (PTRACE_EVENT_SECCOMP << 8):
-		actual_size = ptrace_get_syscall_info_seccomp(child, regs,
-							      &info);
+		return PTRACE_SYSCALL_INFO_SECCOMP;
+	default:
+		return PTRACE_SYSCALL_INFO_NONE;
+	}
+}
+
+static int
+ptrace_get_syscall_info(struct task_struct *child, unsigned long user_size,
+			void __user *datavp)
+{
+	struct pt_regs *regs = task_pt_regs(child);
+	struct ptrace_syscall_info info = {
+		.op = ptrace_get_syscall_info_op(child),
+		.arch = syscall_get_arch(child),
+		.instruction_pointer = instruction_pointer(regs),
+		.stack_pointer = user_stack_pointer(regs),
+	};
+	unsigned long actual_size = offsetof(struct ptrace_syscall_info, entry);
+	unsigned long write_size;
+
+	switch (info.op) {
+	case PTRACE_SYSCALL_INFO_ENTRY:
+		actual_size = ptrace_get_syscall_info_entry(child, regs, &info);
+		break;
+	case PTRACE_SYSCALL_INFO_EXIT:
+		actual_size = ptrace_get_syscall_info_exit(child, regs, &info);
+		break;
+	case PTRACE_SYSCALL_INFO_SECCOMP:
+		actual_size = ptrace_get_syscall_info_seccomp(child, regs, &info);
 		break;
 	}
 
 	write_size = min(actual_size, user_size);
 	return copy_to_user(datavp, &info, write_size) ? -EFAULT : actual_size;
 }
+
+static int
+ptrace_set_syscall_info_entry(struct task_struct *child, struct pt_regs *regs,
+			      struct ptrace_syscall_info *info)
+{
+	unsigned long args[ARRAY_SIZE(info->entry.args)];
+	int nr = info->entry.nr;
+	int i;
+
+	/*
+	 * Check that the syscall number specified in info->entry.nr
+	 * is either a value of type "int" or a sign-extended value
+	 * of type "int".
+	 */
+	if (nr != info->entry.nr)
+		return -ERANGE;
+
+	for (i = 0; i < ARRAY_SIZE(args); i++) {
+		args[i] = info->entry.args[i];
+		/*
+		 * Check that the syscall argument specified in
+		 * info->entry.args[i] is either a value of type
+		 * "unsigned long" or a sign-extended value of type "long".
+		 */
+		if (args[i] != info->entry.args[i])
+			return -ERANGE;
+	}
+
+	syscall_set_nr(child, regs, nr);
+	/*
+	 * If the syscall number is set to -1, setting syscall arguments is not
+	 * just pointless, it would also clobber the syscall return value on
+	 * those architectures that share the same register both for the first
+	 * argument of syscall and its return value.
+	 */
+	if (nr != -1)
+		syscall_set_arguments(child, regs, args);
+
+	return 0;
+}
+
+static int
+ptrace_set_syscall_info_seccomp(struct task_struct *child, struct pt_regs *regs,
+				struct ptrace_syscall_info *info)
+{
+	/*
+	 * info->entry is currently a subset of info->seccomp,
+	 * info->seccomp.ret_data is currently ignored.
+	 */
+	return ptrace_set_syscall_info_entry(child, regs, info);
+}
+
+static int
+ptrace_set_syscall_info_exit(struct task_struct *child, struct pt_regs *regs,
+			     struct ptrace_syscall_info *info)
+{
+	long rval = info->exit.rval;
+
+	/*
+	 * Check that the return value specified in info->exit.rval
+	 * is either a value of type "long" or a sign-extended value
+	 * of type "long".
+	 */
+	if (rval != info->exit.rval)
+		return -ERANGE;
+
+	if (info->exit.is_error)
+		syscall_set_return_value(child, regs, rval, 0);
+	else
+		syscall_set_return_value(child, regs, 0, rval);
+
+	return 0;
+}
+
+static int
+ptrace_set_syscall_info(struct task_struct *child, unsigned long user_size,
+			const void __user *datavp)
+{
+	struct pt_regs *regs = task_pt_regs(child);
+	struct ptrace_syscall_info info;
+
+	if (user_size < sizeof(info))
+		return -EINVAL;
+
+	/*
+	 * The compatibility is tracked by info.op and info.flags: if user-space
+	 * does not instruct us to use unknown extra bits from future versions
+	 * of ptrace_syscall_info, we are not going to read them either.
+	 */
+	if (copy_from_user(&info, datavp, sizeof(info)))
+		return -EFAULT;
+
+	/* Reserved for future use. */
+	if (info.flags || info.reserved)
+		return -EINVAL;
+
+	/* Changing the type of the system call stop is not supported yet. */
+	if (ptrace_get_syscall_info_op(child) != info.op)
+		return -EINVAL;
+
+	switch (info.op) {
+	case PTRACE_SYSCALL_INFO_ENTRY:
+		return ptrace_set_syscall_info_entry(child, regs, &info);
+	case PTRACE_SYSCALL_INFO_EXIT:
+		return ptrace_set_syscall_info_exit(child, regs, &info);
+	case PTRACE_SYSCALL_INFO_SECCOMP:
+		return ptrace_set_syscall_info_seccomp(child, regs, &info);
+	default:
+		/* Other types of system call stops are not supported yet. */
+		return -EINVAL;
+	}
+}
 #endif /* CONFIG_HAVE_ARCH_TRACEHOOK */
 
 int ptrace_request(struct task_struct *child, long request,
@@ -1224,6 +1375,10 @@ int ptrace_request(struct task_struct *child, long request,
 	case PTRACE_GET_SYSCALL_INFO:
 		ret = ptrace_get_syscall_info(child, addr, datavp);
 		break;
+
+	case PTRACE_SET_SYSCALL_INFO:
+		ret = ptrace_set_syscall_info(child, addr, datavp);
+		break;
 #endif
 
 	case PTRACE_SECCOMP_GET_FILTER: