From 3c2eafb460eaca2ea2c3ae62b10f0da3cfa2d915 Mon Sep 17 00:00:00 2001
From: Saied Kazemi <sidkaz@yahoo.com>
Date: Sun, 7 Sep 2014 23:15:58 -0700
Subject: [PATCH] Return AUFS root mountpoint if mnt_id is not found

When reading mnt_id from /proc/<pid>/fdinfo/<fd> for AUFS files in the
/proc/<pid>/map_files directory, the mnt_id value can be for a mountpoint
that is not visible in the process's mount namespace.  In such a case,
instead of failing use the process's root mountpoint.

Signed-off-by: Saied Kazemi <sidkaz@yahoo.com>
---
 crtools.c |  5 +++++
 mount.c   | 14 +++++++++-----
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/crtools.c b/crtools.c
index 1c31392..75ad209 100644
--- a/crtools.c
+++ b/crtools.c
@@ -176,6 +176,7 @@ int main(int argc, char *argv[], char *envp[])
 		{ "exec-cmd", no_argument, 0, 1059},
 		{ "manage-cgroups", no_argument, 0, 1060},
 		{ "cgroup-root", required_argument, 0, 1061},
+		{ "aufs", no_argument, 0, 1062},
 		{ },
 	};
 
@@ -399,6 +400,9 @@ int main(int argc, char *argv[], char *envp[])
 		case 'h':
 			usage_error = false;
 			goto usage;
+		case 1062:
+			opts.aufs = 1;
+			break;
 		default:
 			goto usage;
 		}
@@ -550,6 +554,7 @@ usage:
 "                        'fpu','all'. To disable capability, prefix it with '^'.\n"
 "     --exec-cmd         execute the command specified after '--' on successful\n"
 "                        restore making it the parent of the restored process\n"
+"     --aufs             root filesystem is an AUFS mountpoint\n"
 "\n"
 "* Special resources support:\n"
 "  -x|--" USK_EXT_PARAM "      allow external unix connections\n"
diff --git a/mount.c b/mount.c
index f7bb5f0..9e7df0b 100644
--- a/mount.c
+++ b/mount.c
@@ -137,20 +137,24 @@ int open_mount(unsigned int s_dev)
 	return -ENOENT;
 }
 
-static struct mount_info *__lookup_mnt_id(struct mount_info *list, int id)
+static struct mount_info *__lookup_mnt_id(struct mount_info *list, int id, int root_ok)
 {
 	struct mount_info *m;
+	struct mount_info *root_mount = NULL;
 
-	for (m = list; m != NULL; m = m->next)
+	for (m = list; m != NULL; m = m->next) {
 		if (m->mnt_id == id)
 			return m;
+		if (root_ok && is_root_mount(m))
+			root_mount = m;
+	}
 
-	return NULL;
+	return root_ok ? root_mount : NULL;
 }
 
 struct mount_info *lookup_mnt_id(unsigned int id)
 {
-	return __lookup_mnt_id(mntinfo, id);
+	return __lookup_mnt_id(mntinfo, id, opts.aufs ? 1 : 0);
 }
 
 struct mount_info *lookup_mnt_sdev(unsigned int s_dev)
@@ -251,7 +255,7 @@ static struct mount_info *mnt_build_ids_tree(struct mount_info *list)
 		struct mount_info *p;
 
 		pr_debug("\t\tWorking on %d->%d\n", m->mnt_id, m->parent_mnt_id);
-		p = __lookup_mnt_id(list, m->parent_mnt_id);
+		p = __lookup_mnt_id(list, m->parent_mnt_id, 0);
 		if (!p) {
 			/* This should be / */
 			if (root == NULL && is_root_mount(m)) {
-- 
1.9.1