diff options
Diffstat (limited to 'fs/overlayfs')
| -rw-r--r-- | fs/overlayfs/Kconfig | 14 | ||||
| -rw-r--r-- | fs/overlayfs/export.c | 216 | ||||
| -rw-r--r-- | fs/overlayfs/inode.c | 58 | ||||
| -rw-r--r-- | fs/overlayfs/namei.c | 6 | ||||
| -rw-r--r-- | fs/overlayfs/overlayfs.h | 1 | ||||
| -rw-r--r-- | fs/overlayfs/super.c | 1 |
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)); |