ovl: add NULL check in ovl_alloc_inode

[mirror_ubuntu-artful-kernel.git] / fs / overlayfs / super.c

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index d86e89f972016b4046b20a7a45c2f3f436c50f02..d9bc32d2e6bb25e777f9ded189ee6d1147ebb19c 100644 (file)
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -174,6 +174,9 @@ static struct inode *ovl_alloc_inode(struct super_block *sb)
 {
        struct ovl_inode *oi = kmem_cache_alloc(ovl_inode_cachep, GFP_KERNEL);
 
+       if (!oi)
+               return NULL;
+
        oi->cache = NULL;
        oi->redirect = NULL;
        oi->version = 0;
@@ -210,9 +213,10 @@ static void ovl_put_super(struct super_block *sb)
 
        dput(ufs->indexdir);
        dput(ufs->workdir);
-       ovl_inuse_unlock(ufs->workbasedir);
+       if (ufs->workdir_locked)
+               ovl_inuse_unlock(ufs->workbasedir);
        dput(ufs->workbasedir);
-       if (ufs->upper_mnt)
+       if (ufs->upper_mnt && ufs->upperdir_locked)
                ovl_inuse_unlock(ufs->upper_mnt->mnt_root);
        mntput(ufs->upper_mnt);
        for (i = 0; i < ufs->numlower; i++)
@@ -880,9 +884,13 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
                        goto out_put_upperpath;
 
                err = -EBUSY;
-               if (!ovl_inuse_trylock(upperpath.dentry)) {
-                       pr_err("overlayfs: upperdir is in-use by another mount\n");
+               if (ovl_inuse_trylock(upperpath.dentry)) {
+                       ufs->upperdir_locked = true;
+               } else if (ufs->config.index) {
+                       pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
                        goto out_put_upperpath;
+               } else {
+                       pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
                }
 
                err = ovl_mount_dir(ufs->config.workdir, &workpath);
@@ -900,9 +908,13 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
                }
 
                err = -EBUSY;
-               if (!ovl_inuse_trylock(workpath.dentry)) {
-                       pr_err("overlayfs: workdir is in-use by another mount\n");
+               if (ovl_inuse_trylock(workpath.dentry)) {
+                       ufs->workdir_locked = true;
+               } else if (ufs->config.index) {
+                       pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n");
                        goto out_put_workpath;
+               } else {
+                       pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
                }
 
                ufs->workbasedir = workpath.dentry;
@@ -960,6 +972,9 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 
                sb->s_time_gran = ufs->upper_mnt->mnt_sb->s_time_gran;
 
+               if (ufs->upper_mnt->mnt_flags & MNT_NOSUID)
+                       sb->s_iflags |= SB_I_NOSUID;
+
                ufs->workdir = ovl_workdir_create(sb, ufs, workpath.dentry,
                                                  OVL_WORKDIR_NAME, false);
                /*
@@ -1031,6 +1046,9 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
                 */
                mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
 
+               if (mnt->mnt_flags & MNT_NOSUID)
+                       sb->s_iflags |= SB_I_NOSUID;
+
                ufs->lower_mnt[ufs->numlower] = mnt;
                ufs->numlower++;
 
@@ -1155,11 +1173,13 @@ out_put_lowerpath:
 out_free_lowertmp:
        kfree(lowertmp);
 out_unlock_workdentry:
-       ovl_inuse_unlock(workpath.dentry);
+       if (ufs->workdir_locked)
+               ovl_inuse_unlock(workpath.dentry);
 out_put_workpath:
        path_put(&workpath);
 out_unlock_upperdentry:
-       ovl_inuse_unlock(upperpath.dentry);
+       if (ufs->upperdir_locked)
+               ovl_inuse_unlock(upperpath.dentry);
 out_put_upperpath:
        path_put(&upperpath);
 out_free_config:
@@ -1182,6 +1202,7 @@ static struct file_system_type ovl_fs_type = {
        .name           = "overlay",
        .mount          = ovl_mount,
        .kill_sb        = kill_anon_super,
+       .fs_flags       = FS_USERNS_MOUNT,
 };
 MODULE_ALIAS_FS("overlay");