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authorLinus Torvalds <torvalds@linux-foundation.org>2018-03-09 09:46:14 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2018-03-09 09:46:14 -0800
commit719ea86151f31f9d30dc854e028d05dc4afb3224 (patch)
treeaf46f4307cc5c730baabfe25b8939011ee2dfd3d /fs
parent2d9b1d69c3e2f1cc82029e58f36c4f0fa19984ef (diff)
parent36cd95dfa1ed76b59e2dcaafaa89c5479cec32b5 (diff)
Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs
Pull overlayfs fixes from Miklos Szeredi: "This fixes a corner case for NFS exporting (introduced in this cycle) as well as fixing miscellaneous bugs" * 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs: ovl: update Kconfig texts ovl: redirect_dir=nofollow should not follow redirect for opaque lower ovl: fix ptr_ret.cocci warnings ovl: check ERR_PTR() return value from ovl_lookup_real() ovl: check lower ancestry on encode of lower dir file handle ovl: hash non-dir by lower inode for fsnotify
Diffstat (limited to 'fs')
-rw-r--r--fs/overlayfs/Kconfig14
-rw-r--r--fs/overlayfs/export.c216
-rw-r--r--fs/overlayfs/inode.c58
-rw-r--r--fs/overlayfs/namei.c6
-rw-r--r--fs/overlayfs/overlayfs.h1
-rw-r--r--fs/overlayfs/super.c1
6 files changed, 228 insertions, 68 deletions
diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig
index 406e72de88f6..ce6ff5a0a6e4 100644
--- a/fs/overlayfs/Kconfig
+++ b/fs/overlayfs/Kconfig
@@ -24,6 +24,8 @@ config OVERLAY_FS_REDIRECT_DIR
an overlay which has redirects on a kernel that doesn't support this
feature will have unexpected results.
+ If unsure, say N.
+
config OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW
bool "Overlayfs: follow redirects even if redirects are turned off"
default y
@@ -32,8 +34,13 @@ config OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW
Disable this to get a possibly more secure configuration, but that
might not be backward compatible with previous kernels.
+ If backward compatibility is not an issue, then it is safe and
+ recommended to say N here.
+
For more information, see Documentation/filesystems/overlayfs.txt
+ If unsure, say Y.
+
config OVERLAY_FS_INDEX
bool "Overlayfs: turn on inodes index feature by default"
depends on OVERLAY_FS
@@ -51,6 +58,8 @@ config OVERLAY_FS_INDEX
That is, mounting an overlay which has an inodes index on a kernel
that doesn't support this feature will have unexpected results.
+ If unsure, say N.
+
config OVERLAY_FS_NFS_EXPORT
bool "Overlayfs: turn on NFS export feature by default"
depends on OVERLAY_FS
@@ -72,3 +81,8 @@ config OVERLAY_FS_NFS_EXPORT
Note, that the NFS export feature is not backward compatible.
That is, mounting an overlay which has a full index on a kernel
that doesn't support this feature will have unexpected results.
+
+ Most users should say N here and enable this feature on a case-by-
+ case basis with the "nfs_export=on" mount option.
+
+ Say N unless you fully understand the consequences.
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index bb94ce9da5c8..87bd4148f4fb 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -19,6 +19,142 @@
#include <linux/ratelimit.h>
#include "overlayfs.h"
+static int ovl_encode_maybe_copy_up(struct dentry *dentry)
+{
+ int err;
+
+ if (ovl_dentry_upper(dentry))
+ return 0;
+
+ err = ovl_want_write(dentry);
+ if (!err) {
+ err = ovl_copy_up(dentry);
+ ovl_drop_write(dentry);
+ }
+
+ if (err) {
+ pr_warn_ratelimited("overlayfs: failed to copy up on encode (%pd2, err=%i)\n",
+ dentry, err);
+ }
+
+ return err;
+}
+
+/*
+ * Before encoding a non-upper directory file handle from real layer N, we need
+ * to check if it will be possible to reconnect an overlay dentry from the real
+ * lower decoded dentry. This is done by following the overlay ancestry up to a
+ * "layer N connected" ancestor and verifying that all parents along the way are
+ * "layer N connectable". If an ancestor that is NOT "layer N connectable" is
+ * found, we need to copy up an ancestor, which is "layer N connectable", thus
+ * making that ancestor "layer N connected". For example:
+ *
+ * layer 1: /a
+ * layer 2: /a/b/c
+ *
+ * The overlay dentry /a is NOT "layer 2 connectable", because if dir /a is
+ * copied up and renamed, upper dir /a will be indexed by lower dir /a from
+ * layer 1. The dir /a from layer 2 will never be indexed, so the algorithm (*)
+ * in ovl_lookup_real_ancestor() will not be able to lookup a connected overlay
+ * dentry from the connected lower dentry /a/b/c.
+ *
+ * To avoid this problem on decode time, we need to copy up an ancestor of
+ * /a/b/c, which is "layer 2 connectable", on encode time. That ancestor is
+ * /a/b. After copy up (and index) of /a/b, it will become "layer 2 connected"
+ * and when the time comes to decode the file handle from lower dentry /a/b/c,
+ * ovl_lookup_real_ancestor() will find the indexed ancestor /a/b and decoding
+ * a connected overlay dentry will be accomplished.
+ *
+ * (*) the algorithm in ovl_lookup_real_ancestor() can be improved to lookup an
+ * entry /a in the lower layers above layer N and find the indexed dir /a from
+ * layer 1. If that improvement is made, then the check for "layer N connected"
+ * will need to verify there are no redirects in lower layers above N. In the
+ * example above, /a will be "layer 2 connectable". However, if layer 2 dir /a
+ * is a target of a layer 1 redirect, then /a will NOT be "layer 2 connectable":
+ *
+ * layer 1: /A (redirect = /a)
+ * layer 2: /a/b/c
+ */
+
+/* Return the lowest layer for encoding a connectable file handle */
+static int ovl_connectable_layer(struct dentry *dentry)
+{
+ struct ovl_entry *oe = OVL_E(dentry);
+
+ /* We can get overlay root from root of any layer */
+ if (dentry == dentry->d_sb->s_root)
+ return oe->numlower;
+
+ /*
+ * If it's an unindexed merge dir, then it's not connectable with any
+ * lower layer
+ */
+ if (ovl_dentry_upper(dentry) &&
+ !ovl_test_flag(OVL_INDEX, d_inode(dentry)))
+ return 0;
+
+ /* We can get upper/overlay path from indexed/lower dentry */
+ return oe->lowerstack[0].layer->idx;
+}
+
+/*
+ * @dentry is "connected" if all ancestors up to root or a "connected" ancestor
+ * have the same uppermost lower layer as the origin's layer. We may need to
+ * copy up a "connectable" ancestor to make it "connected". A "connected" dentry
+ * cannot become non "connected", so cache positive result in dentry flags.
+ *
+ * Return the connected origin layer or < 0 on error.
+ */
+static int ovl_connect_layer(struct dentry *dentry)
+{
+ struct dentry *next, *parent = NULL;
+ int origin_layer;
+ int err = 0;
+
+ if (WARN_ON(dentry == dentry->d_sb->s_root) ||
+ WARN_ON(!ovl_dentry_lower(dentry)))
+ return -EIO;
+
+ origin_layer = OVL_E(dentry)->lowerstack[0].layer->idx;
+ if (ovl_dentry_test_flag(OVL_E_CONNECTED, dentry))
+ return origin_layer;
+
+ /* Find the topmost origin layer connectable ancestor of @dentry */
+ next = dget(dentry);
+ for (;;) {
+ parent = dget_parent(next);
+ if (WARN_ON(parent == next)) {
+ err = -EIO;
+ break;
+ }
+
+ /*
+ * If @parent is not origin layer connectable, then copy up
+ * @next which is origin layer connectable and we are done.
+ */
+ if (ovl_connectable_layer(parent) < origin_layer) {
+ err = ovl_encode_maybe_copy_up(next);
+ break;
+ }
+
+ /* If @parent is connected or indexed we are done */
+ if (ovl_dentry_test_flag(OVL_E_CONNECTED, parent) ||
+ ovl_test_flag(OVL_INDEX, d_inode(parent)))
+ break;
+
+ dput(next);
+ next = parent;
+ }
+
+ dput(parent);
+ dput(next);
+
+ if (!err)
+ ovl_dentry_set_flag(OVL_E_CONNECTED, dentry);
+
+ return err ?: origin_layer;
+}
+
/*
* We only need to encode origin if there is a chance that the same object was
* encoded pre copy up and then we need to stay consistent with the same
@@ -41,73 +177,59 @@
* L = lower file handle
*
* (*) Connecting an overlay dir from real lower dentry is not always
- * possible when there are redirects in lower layers. To mitigate this case,
- * we copy up the lower dir first and then encode an upper dir file handle.
+ * possible when there are redirects in lower layers and non-indexed merge dirs.
+ * To mitigate those case, we may copy up the lower dir ancestor before encode
+ * a lower dir file handle.
+ *
+ * Return 0 for upper file handle, > 0 for lower file handle or < 0 on error.
*/
-static bool ovl_should_encode_origin(struct dentry *dentry)
+static int ovl_check_encode_origin(struct dentry *dentry)
{
struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+ /* Upper file handle for pure upper */
if (!ovl_dentry_lower(dentry))
- return false;
+ return 0;
/*
- * Decoding a merge dir, whose origin's parent is under a redirected
- * lower dir is not always possible. As a simple aproximation, we do
- * not encode lower dir file handles when overlay has multiple lower
- * layers and origin is below the topmost lower layer.
+ * Upper file handle for non-indexed upper.
*
- * TODO: copy up only the parent that is under redirected lower.
+ * Root is never indexed, so if there's an upper layer, encode upper for
+ * root.
*/
- if (d_is_dir(dentry) && ofs->upper_mnt &&
- OVL_E(dentry)->lowerstack[0].layer->idx > 1)
- return false;
-
- /* Decoding a non-indexed upper from origin is not implemented */
if (ovl_dentry_upper(dentry) &&
!ovl_test_flag(OVL_INDEX, d_inode(dentry)))
- return false;
-
- return true;
-}
-
-static int ovl_encode_maybe_copy_up(struct dentry *dentry)
-{
- int err;
-
- if (ovl_dentry_upper(dentry))
return 0;
- err = ovl_want_write(dentry);
- if (err)
- return err;
-
- err = ovl_copy_up(dentry);
+ /*
+ * Decoding a merge dir, whose origin's ancestor is under a redirected
+ * lower dir or under a non-indexed upper is not always possible.
+ * ovl_connect_layer() will try to make origin's layer "connected" by
+ * copying up a "connectable" ancestor.
+ */
+ if (d_is_dir(dentry) && ofs->upper_mnt)
+ return ovl_connect_layer(dentry);
- ovl_drop_write(dentry);
- return err;
+ /* Lower file handle for indexed and non-upper dir/non-dir */
+ return 1;
}
static int ovl_d_to_fh(struct dentry *dentry, char *buf, int buflen)
{
- struct dentry *origin = ovl_dentry_lower(dentry);
struct ovl_fh *fh = NULL;
- int err;
+ int err, enc_lower;
/*
- * If we should not encode a lower dir file handle, copy up and encode
- * an upper dir file handle.
+ * Check if we should encode a lower or upper file handle and maybe
+ * copy up an ancestor to make lower file handle connectable.
*/
- if (!ovl_should_encode_origin(dentry)) {
- err = ovl_encode_maybe_copy_up(dentry);
- if (err)
- goto fail;
-
- origin = NULL;
- }
+ err = enc_lower = ovl_check_encode_origin(dentry);
+ if (enc_lower < 0)
+ goto fail;
- /* Encode an upper or origin file handle */
- fh = ovl_encode_fh(origin ?: ovl_dentry_upper(dentry), !origin);
+ /* Encode an upper or lower file handle */
+ fh = ovl_encode_fh(enc_lower ? ovl_dentry_lower(dentry) :
+ ovl_dentry_upper(dentry), !enc_lower);
err = PTR_ERR(fh);
if (IS_ERR(fh))
goto fail;
@@ -355,8 +477,8 @@ static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
dput(upper);
}
- if (!this)
- return NULL;
+ if (IS_ERR_OR_NULL(this))
+ return this;
if (WARN_ON(ovl_dentry_real_at(this, layer->idx) != real)) {
dput(this);
@@ -498,7 +620,7 @@ static struct dentry *ovl_lookup_real(struct super_block *sb,
if (err == -ECHILD) {
this = ovl_lookup_real_ancestor(sb, real,
layer);
- err = IS_ERR(this) ? PTR_ERR(this) : 0;
+ err = PTR_ERR_OR_ZERO(this);
}
if (!err) {
dput(connected);
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index fcd97b783fa1..3b1bd469accd 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -669,38 +669,59 @@ struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *real,
return inode;
}
+/*
+ * Does overlay inode need to be hashed by lower inode?
+ */
+static bool ovl_hash_bylower(struct super_block *sb, struct dentry *upper,
+ struct dentry *lower, struct dentry *index)
+{
+ struct ovl_fs *ofs = sb->s_fs_info;
+
+ /* No, if pure upper */
+ if (!lower)
+ return false;
+
+ /* Yes, if already indexed */
+ if (index)
+ return true;
+
+ /* Yes, if won't be copied up */
+ if (!ofs->upper_mnt)
+ return true;
+
+ /* No, if lower hardlink is or will be broken on copy up */
+ if ((upper || !ovl_indexdir(sb)) &&
+ !d_is_dir(lower) && d_inode(lower)->i_nlink > 1)
+ return false;
+
+ /* No, if non-indexed upper with NFS export */
+ if (sb->s_export_op && upper)
+ return false;
+
+ /* Otherwise, hash by lower inode for fsnotify */
+ return true;
+}
+
struct inode *ovl_get_inode(struct super_block *sb, struct dentry *upperdentry,
struct dentry *lowerdentry, struct dentry *index,
unsigned int numlower)
{
- struct ovl_fs *ofs = sb->s_fs_info;
struct inode *realinode = upperdentry ? d_inode(upperdentry) : NULL;
struct inode *inode;
- /* Already indexed or could be indexed on copy up? */
- bool indexed = (index || (ovl_indexdir(sb) && !upperdentry));
- struct dentry *origin = indexed ? lowerdentry : NULL;
+ bool bylower = ovl_hash_bylower(sb, upperdentry, lowerdentry, index);
bool is_dir;
- if (WARN_ON(upperdentry && indexed && !lowerdentry))
- return ERR_PTR(-EIO);
-
if (!realinode)
realinode = d_inode(lowerdentry);
/*
- * Copy up origin (lower) may exist for non-indexed non-dir upper, but
- * we must not use lower as hash key in that case.
- * Hash non-dir that is or could be indexed by origin inode.
- * Hash dir that is or could be merged by origin inode.
- * Hash pure upper and non-indexed non-dir by upper inode.
- * Hash non-indexed dir by upper inode for NFS export.
+ * Copy up origin (lower) may exist for non-indexed upper, but we must
+ * not use lower as hash key if this is a broken hardlink.
*/
is_dir = S_ISDIR(realinode->i_mode);
- if (is_dir && (indexed || !sb->s_export_op || !ofs->upper_mnt))
- origin = lowerdentry;
-
- if (upperdentry || origin) {
- struct inode *key = d_inode(origin ?: upperdentry);
+ if (upperdentry || bylower) {
+ struct inode *key = d_inode(bylower ? lowerdentry :
+ upperdentry);
unsigned int nlink = is_dir ? 1 : realinode->i_nlink;
inode = iget5_locked(sb, (unsigned long) key,
@@ -728,6 +749,7 @@ struct inode *ovl_get_inode(struct super_block *sb, struct dentry *upperdentry,
nlink = ovl_get_nlink(lowerdentry, upperdentry, nlink);
set_nlink(inode, nlink);
} else {
+ /* Lower hardlink that will be broken on copy up */
inode = new_inode(sb);
if (!inode)
goto out_nomem;
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index de3e6da1d5a5..70fcfcc684cc 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -913,9 +913,6 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
stack[ctr].layer = lower.layer;
ctr++;
- if (d.stop)
- break;
-
/*
* Following redirects can have security consequences: it's like
* a symlink into the lower layer without the permission checks.
@@ -933,6 +930,9 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
goto out_put;
}
+ if (d.stop)
+ break;
+
if (d.redirect && d.redirect[0] == '/' && poe != roe) {
poe = roe;
/* Find the current layer on the root dentry */
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 0df25a9c94bd..225ff1171147 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -40,6 +40,7 @@ enum ovl_inode_flag {
enum ovl_entry_flag {
OVL_E_UPPER_ALIAS,
OVL_E_OPAQUE,
+ OVL_E_CONNECTED,
};
/*
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 9ee37c76091d..7c24619ae7fc 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1359,6 +1359,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
/* Root is always merge -> can have whiteouts */
ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
+ ovl_dentry_set_flag(OVL_E_CONNECTED, root_dentry);
ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
ovl_dentry_lower(root_dentry));