diff --git a/Documentation/filesystems/overlayfs.txt b/Documentation/filesystems/overlayfs.txt
index eef7d9d259e8570d102be8c7f1641158950262c2..1da2f1668f0891a9151cd27218f4e1f6ca5c3732 100644
--- a/Documentation/filesystems/overlayfs.txt
+++ b/Documentation/filesystems/overlayfs.txt
@@ -336,8 +336,20 @@ the copied layers will fail the verification of the lower root file handle.
Non-standard behavior
---------------------
-Overlayfs can now act as a POSIX compliant filesystem with the following
-features turned on:
+Current version of overlayfs can act as a mostly POSIX compliant
+filesystem.
+
+This is the list of cases that overlayfs doesn't currently handle:
+
+a) POSIX mandates updating st_atime for reads. This is currently not
+done in the case when the file resides on a lower layer.
+
+b) If a file residing on a lower layer is opened for read-only and then
+memory mapped with MAP_SHARED, then subsequent changes to the file are not
+reflected in the memory mapping.
+
+The following options allow overlayfs to act more like a standards
+compliant filesystem:
1) "redirect_dir"
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 540a8b8451452f2b624121556e55066b507c353c..340a6ad45914fb01d59fbb386597d9f5d7830a95 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -426,7 +426,8 @@ static unsigned int ovl_get_inode_flags(struct inode *inode)
return ovl_iflags;
}
-static long ovl_ioctl_set_flags(struct file *file, unsigned long arg)
+static long ovl_ioctl_set_flags(struct file *file, unsigned int cmd,
+ unsigned long arg)
{
long ret;
struct inode *inode = file_inode(file);
@@ -456,7 +457,7 @@ static long ovl_ioctl_set_flags(struct file *file, unsigned long arg)
if (ret)
goto unlock;
- ret = ovl_real_ioctl(file, FS_IOC_SETFLAGS, arg);
+ ret = ovl_real_ioctl(file, cmd, arg);
ovl_copyflags(ovl_inode_real(inode), inode);
unlock:
@@ -474,11 +475,13 @@ static long ovl_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
switch (cmd) {
case FS_IOC_GETFLAGS:
+ case FS_IOC_FSGETXATTR:
ret = ovl_real_ioctl(file, cmd, arg);
break;
case FS_IOC_SETFLAGS:
- ret = ovl_ioctl_set_flags(file, arg);
+ case FS_IOC_FSSETXATTR:
+ ret = ovl_ioctl_set_flags(file, cmd, arg);
break;
default:
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index b48273e846adc524eeaa50bde608a93b8bdeb102..f7eba21effa5dbf8c0d5fdb4d922d81f32111cc3 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -777,6 +777,54 @@ struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *real,
return inode;
}
+bool ovl_lookup_trap_inode(struct super_block *sb, struct dentry *dir)
+{
+ struct inode *key = d_inode(dir);
+ struct inode *trap;
+ bool res;
+
+ trap = ilookup5(sb, (unsigned long) key, ovl_inode_test, key);
+ if (!trap)
+ return false;
+
+ res = IS_DEADDIR(trap) && !ovl_inode_upper(trap) &&
+ !ovl_inode_lower(trap);
+
+ iput(trap);
+ return res;
+}
+
+/*
+ * Create an inode cache entry for layer root dir, that will intentionally
+ * fail ovl_verify_inode(), so any lookup that will find some layer root
+ * will fail.
+ */
+struct inode *ovl_get_trap_inode(struct super_block *sb, struct dentry *dir)
+{
+ struct inode *key = d_inode(dir);
+ struct inode *trap;
+
+ if (!d_is_dir(dir))
+ return ERR_PTR(-ENOTDIR);
+
+ trap = iget5_locked(sb, (unsigned long) key, ovl_inode_test,
+ ovl_inode_set, key);
+ if (!trap)
+ return ERR_PTR(-ENOMEM);
+
+ if (!(trap->i_state & I_NEW)) {
+ /* Conflicting layer roots? */
+ iput(trap);
+ return ERR_PTR(-ELOOP);
+ }
+
+ trap->i_mode = S_IFDIR;
+ trap->i_flags = S_DEAD;
+ unlock_new_inode(trap);
+
+ return trap;
+}
+
/*
* Does overlay inode need to be hashed by lower inode?
*/
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index efd372312ef1000709827eab0291b760ea224ae1..badf039267a2fdb415fdcbb1493dc2db1d4ecd35 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -18,6 +18,7 @@
#include "overlayfs.h"
struct ovl_lookup_data {
+ struct super_block *sb;
struct qstr name;
bool is_dir;
bool opaque;
@@ -244,6 +245,12 @@ static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
if (!d->metacopy || d->last)
goto out;
} else {
+ if (ovl_lookup_trap_inode(d->sb, this)) {
+ /* Caught in a trap of overlapping layers */
+ err = -ELOOP;
+ goto out_err;
+ }
+
if (last_element)
d->is_dir = true;
if (d->last)
@@ -819,6 +826,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
int err;
bool metacopy = false;
struct ovl_lookup_data d = {
+ .sb = dentry->d_sb,
.name = dentry->d_name,
.is_dir = false,
.opaque = false,
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index d26efed9f80af753767fbac1b28f38edacc491ea..cec40077b522456fb9b3daa1ea6c886090eeedae 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -270,6 +270,7 @@ void ovl_clear_flag(unsigned long flag, struct inode *inode);
bool ovl_test_flag(unsigned long flag, struct inode *inode);
bool ovl_inuse_trylock(struct dentry *dentry);
void ovl_inuse_unlock(struct dentry *dentry);
+bool ovl_is_inuse(struct dentry *dentry);
bool ovl_need_index(struct dentry *dentry);
int ovl_nlink_start(struct dentry *dentry);
void ovl_nlink_end(struct dentry *dentry);
@@ -376,6 +377,8 @@ struct ovl_inode_params {
struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev);
struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *real,
bool is_upper);
+bool ovl_lookup_trap_inode(struct super_block *sb, struct dentry *dir);
+struct inode *ovl_get_trap_inode(struct super_block *sb, struct dentry *dir);
struct inode *ovl_get_inode(struct super_block *sb,
struct ovl_inode_params *oip);
static inline void ovl_copyattr(struct inode *from, struct inode *to)
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index ec237035333afcbb8ffab21951a172e384a6597a..6ed1ace8f8b30092e9455de3ace45461d53a2eeb 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -29,6 +29,8 @@ struct ovl_sb {
struct ovl_layer {
struct vfsmount *mnt;
+ /* Trap in ovl inode cache */
+ struct inode *trap;
struct ovl_sb *fs;
/* Index of this layer in fs root (upper idx == 0) */
int idx;
@@ -65,6 +67,10 @@ struct ovl_fs {
/* Did we take the inuse lock? */
bool upperdir_locked;
bool workdir_locked;
+ /* Traps in ovl inode cache */
+ struct inode *upperdir_trap;
+ struct inode *workdir_trap;
+ struct inode *indexdir_trap;
/* Inode numbers in all layers do not use the high xino_bits */
unsigned int xino_bits;
};
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 5ec4fc2f5d7e7cd0b9ccf8816e84bda38805306d..746ea36f3171d5e5ef75bbf108ee3b2e004af93a 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -215,6 +215,9 @@ static void ovl_free_fs(struct ovl_fs *ofs)
{
unsigned i;
+ iput(ofs->indexdir_trap);
+ iput(ofs->workdir_trap);
+ iput(ofs->upperdir_trap);
dput(ofs->indexdir);
dput(ofs->workdir);
if (ofs->workdir_locked)
@@ -223,8 +226,10 @@ static void ovl_free_fs(struct ovl_fs *ofs)
if (ofs->upperdir_locked)
ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
mntput(ofs->upper_mnt);
- for (i = 0; i < ofs->numlower; i++)
+ for (i = 0; i < ofs->numlower; i++) {
+ iput(ofs->lower_layers[i].trap);
mntput(ofs->lower_layers[i].mnt);
+ }
for (i = 0; i < ofs->numlowerfs; i++)
free_anon_bdev(ofs->lower_fs[i].pseudo_dev);
kfree(ofs->lower_layers);
@@ -983,7 +988,26 @@ static const struct xattr_handler *ovl_xattr_handlers[] = {
NULL
};
-static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath)
+static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
+ struct inode **ptrap, const char *name)
+{
+ struct inode *trap;
+ int err;
+
+ trap = ovl_get_trap_inode(sb, dir);
+ err = PTR_ERR(trap);
+ if (IS_ERR(trap)) {
+ if (err == -ELOOP)
+ pr_err("overlayfs: conflicting %s path\n", name);
+ return err;
+ }
+
+ *ptrap = trap;
+ return 0;
+}
+
+static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
+ struct path *upperpath)
{
struct vfsmount *upper_mnt;
int err;
@@ -1003,6 +1027,11 @@ static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath)
if (err)
goto out;
+ err = ovl_setup_trap(sb, upperpath->dentry, &ofs->upperdir_trap,
+ "upperdir");
+ if (err)
+ goto out;
+
upper_mnt = clone_private_mount(upperpath);
err = PTR_ERR(upper_mnt);
if (IS_ERR(upper_mnt)) {
@@ -1029,7 +1058,8 @@ static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath)
return err;
}
-static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath)
+static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
+ struct path *workpath)
{
struct vfsmount *mnt = ofs->upper_mnt;
struct dentry *temp;
@@ -1044,6 +1074,10 @@ static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath)
if (!ofs->workdir)
goto out;
+ err = ovl_setup_trap(sb, ofs->workdir, &ofs->workdir_trap, "workdir");
+ if (err)
+ goto out;
+
/*
* Upper should support d_type, else whiteouts are visible. Given
* workdir and upper are on same fs, we can do iterate_dir() on
@@ -1104,7 +1138,8 @@ static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath)
return err;
}
-static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath)
+static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs,
+ struct path *upperpath)
{
int err;
struct path workpath = { };
@@ -1135,19 +1170,16 @@ static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath)
pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
}
- err = ovl_make_workdir(ofs, &workpath);
- if (err)
- goto out;
+ err = ovl_make_workdir(sb, ofs, &workpath);
- err = 0;
out:
path_put(&workpath);
return err;
}
-static int ovl_get_indexdir(struct ovl_fs *ofs, struct ovl_entry *oe,
- struct path *upperpath)
+static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
+ struct ovl_entry *oe, struct path *upperpath)
{
struct vfsmount *mnt = ofs->upper_mnt;
int err;
@@ -1166,6 +1198,11 @@ static int ovl_get_indexdir(struct ovl_fs *ofs, struct ovl_entry *oe,
ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
if (ofs->indexdir) {
+ err = ovl_setup_trap(sb, ofs->indexdir, &ofs->indexdir_trap,
+ "indexdir");
+ if (err)
+ goto out;
+
/*
* Verify upper root is exclusively associated with index dir.
* Older kernels stored upper fh in "trusted.overlay.origin"
@@ -1253,8 +1290,8 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
return ofs->numlowerfs;
}
-static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
- unsigned int numlower)
+static int ovl_get_lower_layers(struct super_block *sb, struct ovl_fs *ofs,
+ struct path *stack, unsigned int numlower)
{
int err;
unsigned int i;
@@ -1272,16 +1309,28 @@ static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
for (i = 0; i < numlower; i++) {
struct vfsmount *mnt;
+ struct inode *trap;
int fsid;
err = fsid = ovl_get_fsid(ofs, &stack[i]);
if (err < 0)
goto out;
+ err = -EBUSY;
+ if (ovl_is_inuse(stack[i].dentry)) {
+ pr_err("overlayfs: lowerdir is in-use as upperdir/workdir\n");
+ goto out;
+ }
+
+ err = ovl_setup_trap(sb, stack[i].dentry, &trap, "lowerdir");
+ if (err)
+ goto out;
+
mnt = clone_private_mount(&stack[i]);
err = PTR_ERR(mnt);
if (IS_ERR(mnt)) {
pr_err("overlayfs: failed to clone lowerpath\n");
+ iput(trap);
goto out;
}
@@ -1291,6 +1340,7 @@ static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
*/
mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
+ ofs->lower_layers[ofs->numlower].trap = trap;
ofs->lower_layers[ofs->numlower].mnt = mnt;
ofs->lower_layers[ofs->numlower].idx = i + 1;
ofs->lower_layers[ofs->numlower].fsid = fsid;
@@ -1385,7 +1435,7 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
goto out_err;
}
- err = ovl_get_lower_layers(ofs, stack, numlower);
+ err = ovl_get_lower_layers(sb, ofs, stack, numlower);
if (err)
goto out_err;
@@ -1417,6 +1467,85 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
goto out;
}
+/*
+ * Check if this layer root is a descendant of:
+ * - another layer of this overlayfs instance
+ * - upper/work dir of any overlayfs instance
+ * - a disconnected dentry (detached root)
+ */
+static int ovl_check_layer(struct super_block *sb, struct dentry *dentry,
+ const char *name)
+{
+ struct dentry *next, *parent;
+ bool is_root = false;
+ int err = 0;
+
+ if (!dentry || dentry == dentry->d_sb->s_root)
+ return 0;
+
+ next = dget(dentry);
+ /* Walk back ancestors to fs root (inclusive) looking for traps */
+ do {
+ parent = dget_parent(next);
+ is_root = (parent == next);
+ if (ovl_is_inuse(parent)) {
+ err = -EBUSY;
+ pr_err("overlayfs: %s path overlapping in-use upperdir/workdir\n",
+ name);
+ } else if (ovl_lookup_trap_inode(sb, parent)) {
+ err = -ELOOP;
+ pr_err("overlayfs: overlapping %s path\n", name);
+ }
+ dput(next);
+ next = parent;
+ } while (!err && !is_root);
+
+ /* Did we really walk to fs root or found a detached root? */
+ if (!err && next != dentry->d_sb->s_root) {
+ err = -ESTALE;
+ pr_err("overlayfs: disconnected %s path\n", name);
+ }
+
+ dput(next);
+
+ return err;
+}
+
+/*
+ * Check if any of the layers or work dirs overlap.
+ */
+static int ovl_check_overlapping_layers(struct super_block *sb,
+ struct ovl_fs *ofs)
+{
+ int i, err;
+
+ if (ofs->upper_mnt) {
+ err = ovl_check_layer(sb, ofs->upper_mnt->mnt_root, "upperdir");
+ if (err)
+ return err;
+
+ /*
+ * Checking workbasedir avoids hitting ovl_is_inuse(parent) of
+ * this instance and covers overlapping work and index dirs,
+ * unless work or index dir have been moved since created inside
+ * workbasedir. In that case, we already have their traps in
+ * inode cache and we will catch that case on lookup.
+ */
+ err = ovl_check_layer(sb, ofs->workbasedir, "workdir");
+ if (err)
+ return err;
+ }
+
+ for (i = 0; i < ofs->numlower; i++) {
+ err = ovl_check_layer(sb, ofs->lower_layers[i].mnt->mnt_root,
+ "lowerdir");
+ if (err)
+ return err;
+ }
+
+ return 0;
+}
+
static int ovl_fill_super(struct super_block *sb, void *data, int silent)
{
struct path upperpath = { };
@@ -1456,17 +1585,20 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
if (ofs->config.xino != OVL_XINO_OFF)
ofs->xino_bits = BITS_PER_LONG - 32;
+ /* alloc/destroy_inode needed for setting up traps in inode cache */
+ sb->s_op = &ovl_super_operations;
+
if (ofs->config.upperdir) {
if (!ofs->config.workdir) {
pr_err("overlayfs: missing 'workdir'\n");
goto out_err;
}
- err = ovl_get_upper(ofs, &upperpath);
+ err = ovl_get_upper(sb, ofs, &upperpath);
if (err)
goto out_err;
- err = ovl_get_workdir(ofs, &upperpath);
+ err = ovl_get_workdir(sb, ofs, &upperpath);
if (err)
goto out_err;
@@ -1487,7 +1619,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
sb->s_flags |= SB_RDONLY;
if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
- err = ovl_get_indexdir(ofs, oe, &upperpath);
+ err = ovl_get_indexdir(sb, ofs, oe, &upperpath);
if (err)
goto out_free_oe;
@@ -1500,6 +1632,10 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
}
+ err = ovl_check_overlapping_layers(sb, ofs);
+ if (err)
+ goto out_free_oe;
+
/* Show index=off in /proc/mounts for forced r/o mount */
if (!ofs->indexdir) {
ofs->config.index = false;
@@ -1521,7 +1657,6 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
sb->s_magic = OVERLAYFS_SUPER_MAGIC;
- sb->s_op = &ovl_super_operations;
sb->s_xattr = ovl_xattr_handlers;
sb->s_fs_info = ofs;
sb->s_flags |= SB_POSIXACL;
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 4035e640f40211713fca5fea72fe7fb28babcd29..e135064e87ad35b8a93afd60f226e2cd87821c91 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -652,6 +652,18 @@ void ovl_inuse_unlock(struct dentry *dentry)
}
}
+bool ovl_is_inuse(struct dentry *dentry)
+{
+ struct inode *inode = d_inode(dentry);
+ bool inuse;
+
+ spin_lock(&inode->i_lock);
+ inuse = (inode->i_state & I_OVL_INUSE);
+ spin_unlock(&inode->i_lock);
+
+ return inuse;
+}
+
/*
* Does this overlay dentry need to be indexed on copy up?
*/