1 files changed, 68 insertions, 25 deletions

diff --git a/fs/coredump.c b/fs/coredump.c
index a8f75640ac86..47c32c3bfa1d 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -32,6 +32,10 @@
 #include <linux/pipe_fs_i.h>
 #include <linux/oom.h>
 #include <linux/compat.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/path.h>
+#include <linux/timekeeping.h>
 
 #include <asm/uaccess.h>
 #include <asm/mmu_context.h>
@@ -117,6 +121,26 @@ int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
 	ret = cn_vprintf(cn, fmt, arg);
 	va_end(arg);
 
+	if (ret == 0) {
+		/*
+		 * Ensure that this coredump name component can't cause the
+		 * resulting corefile path to consist of a ".." or ".".
+		 */
+		if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
+				(cn->used - cur == 2 && cn->corename[cur] == '.'
+				&& cn->corename[cur+1] == '.'))
+			cn->corename[cur] = '!';
+
+		/*
+		 * Empty names are fishy and could be used to create a "//" in a
+		 * corefile name, causing the coredump to happen one directory
+		 * level too high. Enforce that all components of the core
+		 * pattern are at least one character long.
+		 */
+		if (cn->used == cur)
+			ret = cn_printf(cn, "!");
+	}
+
 	for (; cur < cn->used; ++cur) {
 		if (cn->corename[cur] == '/')
 			cn->corename[cur] = '!';
@@ -232,9 +256,10 @@ static int format_corename(struct core_name *cn, struct coredump_params *cprm)
 				break;
 			/* UNIX time of coredump */
 			case 't': {
-				struct timeval tv;
-				do_gettimeofday(&tv);
-				err = cn_printf(cn, "%lu", tv.tv_sec);
+				time64_t time;
+
+				time = ktime_get_real_seconds();
+				err = cn_printf(cn, "%lld", time);
 				break;
 			}
 			/* hostname */
@@ -280,23 +305,24 @@ out:
 	return ispipe;
 }
 
-static int zap_process(struct task_struct *start, int exit_code)
+static int zap_process(struct task_struct *start, int exit_code, int flags)
 {
 	struct task_struct *t;
 	int nr = 0;
 
+	/* ignore all signals except SIGKILL, see prepare_signal() */
+	start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;
 	start->signal->group_exit_code = exit_code;
 	start->signal->group_stop_count = 0;
 
-	t = start;
-	do {
+	for_each_thread(start, t) {
 		task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
 		if (t != current && t->mm) {
 			sigaddset(&t->pending.signal, SIGKILL);
 			signal_wake_up(t, 1);
 			nr++;
 		}
-	} while_each_thread(start, t);
+	}
 
 	return nr;
 }
@@ -311,10 +337,8 @@ static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
 	spin_lock_irq(&tsk->sighand->siglock);
 	if (!signal_group_exit(tsk->signal)) {
 		mm->core_state = core_state;
-		nr = zap_process(tsk, exit_code);
 		tsk->signal->group_exit_task = tsk;
-		/* ignore all signals except SIGKILL, see prepare_signal() */
-		tsk->signal->flags = SIGNAL_GROUP_COREDUMP;
+		nr = zap_process(tsk, exit_code, 0);
 		clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
 	}
 	spin_unlock_irq(&tsk->sighand->siglock);
@@ -360,18 +384,18 @@ static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
 			continue;
 		if (g->flags & PF_KTHREAD)
 			continue;
-		p = g;
-		do {
-			if (p->mm) {
-				if (unlikely(p->mm == mm)) {
-					lock_task_sighand(p, &flags);
-					nr += zap_process(p, exit_code);
-					p->signal->flags = SIGNAL_GROUP_EXIT;
-					unlock_task_sighand(p, &flags);
-				}
-				break;
+
+		for_each_thread(g, p) {
+			if (unlikely(!p->mm))
+				continue;
+			if (unlikely(p->mm == mm)) {
+				lock_task_sighand(p, &flags);
+				nr += zap_process(p, exit_code,
+							SIGNAL_GROUP_EXIT);
+				unlock_task_sighand(p, &flags);
 			}
-		} while_each_thread(g, p);
+			break;
+		}
 	}
 	rcu_read_unlock();
 done:
@@ -628,6 +652,8 @@ void do_coredump(const siginfo_t *siginfo)
 		}
 	} else {
 		struct inode *inode;
+		int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
+				 O_LARGEFILE | O_EXCL;
 
 		if (cprm.limit < binfmt->min_coredump)
 			goto fail_unlock;
@@ -666,10 +692,27 @@ void do_coredump(const siginfo_t *siginfo)
 		 * what matters is that at least one of the two processes
 		 * writes its coredump successfully, not which one.
 		 */
-		cprm.file = filp_open(cn.corename,
-				 O_CREAT | 2 | O_NOFOLLOW |
-				 O_LARGEFILE | O_EXCL,
-				 0600);
+		if (need_suid_safe) {
+			/*
+			 * Using user namespaces, normal user tasks can change
+			 * their current->fs->root to point to arbitrary
+			 * directories. Since the intention of the "only dump
+			 * with a fully qualified path" rule is to control where
+			 * coredumps may be placed using root privileges,
+			 * current->fs->root must not be used. Instead, use the
+			 * root directory of init_task.
+			 */
+			struct path root;
+
+			task_lock(&init_task);
+			get_fs_root(init_task.fs, &root);
+			task_unlock(&init_task);
+			cprm.file = file_open_root(root.dentry, root.mnt,
+				cn.corename, open_flags, 0600);
+			path_put(&root);
+		} else {
+			cprm.file = filp_open(cn.corename, open_flags, 0600);
+		}
 		if (IS_ERR(cprm.file))
 			goto fail_unlock;