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149 lines
3.9 KiB
Diff
149 lines
3.9 KiB
Diff
Patch by: Miklos Szeredi <miklos@szeredi.hu>
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Some filesystems (e.g. jffs2) lock the same resources for both readdir
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and lookup, leading to a deadlock in ovl_cache_entry_new, which is called
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from the filldir, and calls lookup itself.
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--- a/fs/overlayfs/readdir.c
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+++ b/fs/overlayfs/readdir.c
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@@ -23,6 +23,7 @@ struct ovl_cache_entry {
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u64 ino;
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struct list_head l_node;
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struct rb_node node;
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+ struct ovl_cache_entry *next_maybe_whiteout;
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bool is_whiteout;
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char name[];
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};
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@@ -39,7 +40,7 @@ struct ovl_readdir_data {
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struct rb_root root;
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struct list_head *list;
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struct list_head middle;
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- struct dentry *dir;
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+ struct ovl_cache_entry *first_maybe_whiteout;
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int count;
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int err;
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};
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@@ -79,7 +80,7 @@ static struct ovl_cache_entry *ovl_cache
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return NULL;
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}
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-static struct ovl_cache_entry *ovl_cache_entry_new(struct dentry *dir,
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+static struct ovl_cache_entry *ovl_cache_entry_new(struct ovl_readdir_data *rdd,
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const char *name, int len,
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u64 ino, unsigned int d_type)
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{
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@@ -98,29 +99,8 @@ static struct ovl_cache_entry *ovl_cache
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p->is_whiteout = false;
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if (d_type == DT_CHR) {
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- struct dentry *dentry;
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- const struct cred *old_cred;
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- struct cred *override_cred;
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-
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- override_cred = prepare_creds();
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- if (!override_cred) {
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- kfree(p);
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- return NULL;
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- }
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-
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- /*
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- * CAP_DAC_OVERRIDE for lookup
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- */
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- cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
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- old_cred = override_creds(override_cred);
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-
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- dentry = lookup_one_len(name, dir, len);
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- if (!IS_ERR(dentry)) {
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- p->is_whiteout = ovl_is_whiteout(dentry);
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- dput(dentry);
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- }
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- revert_creds(old_cred);
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- put_cred(override_cred);
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+ p->next_maybe_whiteout = rdd->first_maybe_whiteout;
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+ rdd->first_maybe_whiteout = p;
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}
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return p;
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}
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@@ -148,7 +128,7 @@ static int ovl_cache_entry_add_rb(struct
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return 0;
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}
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- p = ovl_cache_entry_new(rdd->dir, name, len, ino, d_type);
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+ p = ovl_cache_entry_new(rdd, name, len, ino, d_type);
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if (p == NULL)
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return -ENOMEM;
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@@ -169,7 +149,7 @@ static int ovl_fill_lower(struct ovl_rea
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if (p) {
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list_move_tail(&p->l_node, &rdd->middle);
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} else {
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- p = ovl_cache_entry_new(rdd->dir, name, namelen, ino, d_type);
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+ p = ovl_cache_entry_new(rdd, name, namelen, ino, d_type);
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if (p == NULL)
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rdd->err = -ENOMEM;
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else
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@@ -219,6 +199,43 @@ static int ovl_fill_merge(struct dir_con
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return ovl_fill_lower(rdd, name, namelen, offset, ino, d_type);
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}
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+static int ovl_check_whiteouts(struct dentry *dir, struct ovl_readdir_data *rdd)
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+{
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+ int err = 0;
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+
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+ mutex_lock(&dir->d_inode->i_mutex);
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+ while (rdd->first_maybe_whiteout) {
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+ struct dentry *dentry;
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+ const struct cred *old_cred;
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+ struct cred *override_cred;
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+ struct ovl_cache_entry *p = rdd->first_maybe_whiteout;
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+
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+ rdd->first_maybe_whiteout = p->next_maybe_whiteout;
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+
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+ override_cred = prepare_creds();
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+ if (!override_cred) {
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+ err = -ENOMEM;
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+ break;
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+ }
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+ /*
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+ * CAP_DAC_OVERRIDE for lookup
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+ */
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+ cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
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+ old_cred = override_creds(override_cred);
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+
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+ dentry = lookup_one_len(p->name, dir, p->len);
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+ if (!IS_ERR(dentry)) {
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+ p->is_whiteout = ovl_is_whiteout(dentry);
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+ dput(dentry);
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+ }
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+ revert_creds(old_cred);
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+ put_cred(override_cred);
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+ }
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+ mutex_unlock(&dir->d_inode->i_mutex);
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+
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+ return err;
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+}
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+
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static inline int ovl_dir_read(struct path *realpath,
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struct ovl_readdir_data *rdd)
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{
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@@ -229,7 +246,7 @@ static inline int ovl_dir_read(struct pa
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if (IS_ERR(realfile))
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return PTR_ERR(realfile);
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- rdd->dir = realpath->dentry;
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+ rdd->first_maybe_whiteout = NULL;
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rdd->ctx.pos = 0;
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do {
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rdd->count = 0;
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@@ -238,6 +255,10 @@ static inline int ovl_dir_read(struct pa
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if (err >= 0)
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err = rdd->err;
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} while (!err && rdd->count);
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+
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+ if (!err && rdd->first_maybe_whiteout)
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+ err = ovl_check_whiteouts(realpath->dentry, rdd);
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+
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fput(realfile);
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return err;
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