diff --git a/Documentation/filesystems/overlayfs.txt b/Documentation/filesystems/overlayfs.txt
index 36f528a7fdd64d18c7ee7b3a50849b45bc046ef3..8caa60734647f70a777b8a568ba9f2dd99182fb8 100644
--- a/Documentation/filesystems/overlayfs.txt
+++ b/Documentation/filesystems/overlayfs.txt
@@ -210,8 +210,11 @@ path as another overlay mount and it may use a lower layer path that is
beneath or above the path of another overlay lower layer path.
Using an upper layer path and/or a workdir path that are already used by
-another overlay mount is not allowed and will fail with EBUSY. Using
+another overlay mount is not allowed and may fail with EBUSY. Using
partially overlapping paths is not allowed but will not fail with EBUSY.
+If files are accessed from two overlayfs mounts which share or overlap the
+upper layer and/or workdir path the behavior of the overlay is undefined,
+though it will not result in a crash or deadlock.
Mounting an overlay using an upper layer path, where the upper layer path
was previously used by another mounted overlay in combination with a
diff --git a/fs/namespace.c b/fs/namespace.c
index 54059b142d6ba1153b8adab7114cd7587e0c3aad..3b601f115b6cb72a9f02a82f5e8a41c458729b4b 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -468,7 +468,9 @@ static inline int may_write_real(struct file *file)
/* File refers to upper, writable layer? */
upperdentry = d_real(dentry, NULL, 0, D_REAL_UPPER);
- if (upperdentry && file_inode(file) == d_inode(upperdentry))
+ if (upperdentry &&
+ (file_inode(file) == d_inode(upperdentry) ||
+ file_inode(file) == d_inode(dentry)))
return 0;
/* Lower layer: can't write to real file, sorry... */
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index aad97b30d5e657199f741f02700208c41e5424ae..c441f9387a1ba0f2ddf1f1426a114a5533fb6e30 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -561,10 +561,8 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c)
c->tmpfile = true;
err = ovl_copy_up_locked(c);
} else {
- err = -EIO;
- if (lock_rename(c->workdir, c->destdir) != NULL) {
- pr_err("overlayfs: failed to lock workdir+upperdir\n");
- } else {
+ err = ovl_lock_rename_workdir(c->workdir, c->destdir);
+ if (!err) {
err = ovl_copy_up_locked(c);
unlock_rename(c->workdir, c->destdir);
}
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 3309b1912241769bba93e2caba483a4e2f57035a..cc961a3bd3bdec34fcace34553f9e8cfb319db25 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -216,26 +216,6 @@ out_unlock:
return err;
}
-static int ovl_lock_rename_workdir(struct dentry *workdir,
- struct dentry *upperdir)
-{
- /* Workdir should not be the same as upperdir */
- if (workdir == upperdir)
- goto err;
-
- /* Workdir should not be subdir of upperdir and vice versa */
- if (lock_rename(workdir, upperdir) != NULL)
- goto err_unlock;
-
- return 0;
-
-err_unlock:
- unlock_rename(workdir, upperdir);
-err:
- pr_err("overlayfs: failed to lock workdir+upperdir\n");
- return -EIO;
-}
-
static struct dentry *ovl_clear_empty(struct dentry *dentry,
struct list_head *list)
{
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index c3addd1114f1f562464370e6d640abd22cd3a3e4..654bea1a5ac9f38c587919d1fac6d53fd6867ee0 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -506,6 +506,7 @@ static struct dentry *ovl_lookup_index(struct dentry *dentry,
index = lookup_one_len_unlocked(name.name, ofs->indexdir, name.len);
if (IS_ERR(index)) {
+ err = PTR_ERR(index);
pr_warn_ratelimited("overlayfs: failed inode index lookup (ino=%lu, key=%*s, err=%i);\n"
"overlayfs: mount with '-o index=off' to disable inodes index.\n",
d_inode(origin)->i_ino, name.len, name.name,
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index d4e8c1a08fb0f5d7b4c79de7aa88a5211a4996a4..c706a6f999288136b567d75777f5f6742682a9a2 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -235,6 +235,7 @@ bool ovl_inuse_trylock(struct dentry *dentry);
void ovl_inuse_unlock(struct dentry *dentry);
int ovl_nlink_start(struct dentry *dentry, bool *locked);
void ovl_nlink_end(struct dentry *dentry, bool locked);
+int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir);
static inline bool ovl_is_impuredir(struct dentry *dentry)
{
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index 878a750986dd799ad17d9acfc3818e93dcf288fa..25d9b5adcd429071537c5edf3185b58a6ab9cd60 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -37,6 +37,9 @@ struct ovl_fs {
bool noxattr;
/* sb common to all layers */
struct super_block *same_sb;
+ /* Did we take the inuse lock? */
+ bool upperdir_locked;
+ bool workdir_locked;
};
/* private information held for every overlayfs dentry */
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index 62e9b22a2077ac2ac9acb382dd5617a34e9e7636..0f85ee9c3268adb320dcc6c4d37e88ae3ea92013 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -988,6 +988,7 @@ int ovl_indexdir_cleanup(struct dentry *dentry, struct vfsmount *mnt,
struct path *lowerstack, unsigned int numlower)
{
int err;
+ struct dentry *index = NULL;
struct inode *dir = dentry->d_inode;
struct path path = { .mnt = mnt, .dentry = dentry };
LIST_HEAD(list);
@@ -1007,8 +1008,6 @@ int ovl_indexdir_cleanup(struct dentry *dentry, struct vfsmount *mnt,
inode_lock_nested(dir, I_MUTEX_PARENT);
list_for_each_entry(p, &list, l_node) {
- struct dentry *index;
-
if (p->name[0] == '.') {
if (p->len == 1)
continue;
@@ -1018,6 +1017,7 @@ int ovl_indexdir_cleanup(struct dentry *dentry, struct vfsmount *mnt,
index = lookup_one_len(p->name, dentry, p->len);
if (IS_ERR(index)) {
err = PTR_ERR(index);
+ index = NULL;
break;
}
err = ovl_verify_index(index, lowerstack, numlower);
@@ -1029,7 +1029,9 @@ int ovl_indexdir_cleanup(struct dentry *dentry, struct vfsmount *mnt,
break;
}
dput(index);
+ index = NULL;
}
+ dput(index);
inode_unlock(dir);
out:
ovl_cache_free(&list);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index fd5ea4facc622f80861f1495d93b148ecde2a003..092d150643c12061407be0ecab554a38fe88d9fc 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -211,9 +211,10 @@ 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++)
@@ -881,9 +882,13 @@ 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);
@@ -901,9 +906,13 @@ 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;
@@ -1156,11 +1165,13 @@ 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:
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 117794582f9fa597d34d8843aa8bdfb7a99cbe76..b9b239fa5cfd28d18b120696d05e817330e44241 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -430,7 +430,7 @@ void ovl_inuse_unlock(struct dentry *dentry)
}
}
-/* Called must hold OVL_I(inode)->oi_lock */
+/* Caller must hold OVL_I(inode)->lock */
static void ovl_cleanup_index(struct dentry *dentry)
{
struct inode *dir = ovl_indexdir(dentry->d_sb)->d_inode;
@@ -469,6 +469,9 @@ static void ovl_cleanup_index(struct dentry *dentry)
err = PTR_ERR(index);
if (!IS_ERR(index))
err = ovl_cleanup(dir, index);
+ else
+ index = NULL;
+
inode_unlock(dir);
if (err)
goto fail;
@@ -557,3 +560,22 @@ void ovl_nlink_end(struct dentry *dentry, bool locked)
mutex_unlock(&OVL_I(d_inode(dentry))->lock);
}
}
+
+int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir)
+{
+ /* Workdir should not be the same as upperdir */
+ if (workdir == upperdir)
+ goto err;
+
+ /* Workdir should not be subdir of upperdir and vice versa */
+ if (lock_rename(workdir, upperdir) != NULL)
+ goto err_unlock;
+
+ return 0;
+
+err_unlock:
+ unlock_rename(workdir, upperdir);
+err:
+ pr_err("overlayfs: failed to lock workdir+upperdir\n");
+ return -EIO;
+}