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Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs 

Pull overlayfs update from Miklos Szeredi:
 "The meat of this is a change to use the mounter's credentials for
  operations that require elevated privileges (such as whiteout
  creation).  This fixes behavior under user namespaces as well as being
  a nice cleanup"

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: Do d_type check only if work dir creation was successful
  ovl: update documentation
  ovl: override creds with the ones from the superblock mounter
This commit is contained in:
Linus Torvalds 2016-05-27 16:44:39 -07:00
parent 559b6d90a0 21765194ce
commit 0121a32201
6 changed files with 38 additions and 116 deletions
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9
Documentation/filesystems/overlayfs.txt
View File

@ -194,15 +194,6 @@ If a file with multiple hard links is copied up, then this will
"break" the link. Changes will not be propagated to other names
referring to the same inode.
Symlinks in /proc/PID/ and /proc/PID/fd which point to a non-directory
object in overlayfs will not contain valid absolute paths, only
relative paths leading up to the filesystem's root. This will be
fixed in the future.
Some operations are not atomic, for example a crash during copy_up or
rename will leave the filesystem in an inconsistent state. This will
be addressed in the future.
Changes to underlying filesystems
---------------------------------

26
fs/overlayfs/copy_up.c
View File

@ -336,7 +336,6 @@ int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
struct dentry *upperdir;
struct dentry *upperdentry;
const struct cred *old_cred;
struct cred *override_cred;
char *link = NULL;
if (WARN_ON(!workdir))
@ -357,28 +356,7 @@ int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
return PTR_ERR(link);
}
err = -ENOMEM;
override_cred = prepare_creds();
if (!override_cred)
goto out_free_link;
override_cred->fsuid = stat->uid;
override_cred->fsgid = stat->gid;
/*
* CAP_SYS_ADMIN for copying up extended attributes
* CAP_DAC_OVERRIDE for create
* CAP_FOWNER for chmod, timestamp update
* CAP_FSETID for chmod
* CAP_CHOWN for chown
* CAP_MKNOD for mknod
*/
cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
cap_raise(override_cred->cap_effective, CAP_FOWNER);
cap_raise(override_cred->cap_effective, CAP_FSETID);
cap_raise(override_cred->cap_effective, CAP_CHOWN);
cap_raise(override_cred->cap_effective, CAP_MKNOD);
old_cred = override_creds(override_cred);
old_cred = ovl_override_creds(dentry->d_sb);
err = -EIO;
if (lock_rename(workdir, upperdir) != NULL) {
@ -401,9 +379,7 @@ int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
out_unlock:
unlock_rename(workdir, upperdir);
revert_creds(old_cred);
put_cred(override_cred);
out_free_link:
if (link)
free_page((unsigned long) link);

67
fs/overlayfs/dir.c
View File

@ -405,28 +405,13 @@ static int ovl_create_or_link(struct dentry *dentry, int mode, dev_t rdev,
err = ovl_create_upper(dentry, inode, &stat, link, hardlink);
} else {
const struct cred *old_cred;
struct cred *override_cred;
err = -ENOMEM;
override_cred = prepare_creds();
if (!override_cred)
goto out_iput;
/*
* CAP_SYS_ADMIN for setting opaque xattr
* CAP_DAC_OVERRIDE for create in workdir, rename
* CAP_FOWNER for removing whiteout from sticky dir
*/
cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
cap_raise(override_cred->cap_effective, CAP_FOWNER);
old_cred = override_creds(override_cred);
old_cred = ovl_override_creds(dentry->d_sb);
err = ovl_create_over_whiteout(dentry, inode, &stat, link,
hardlink);
revert_creds(old_cred);
put_cred(override_cred);
}
if (!err)
@ -662,32 +647,11 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir)
if (OVL_TYPE_PURE_UPPER(type)) {
err = ovl_remove_upper(dentry, is_dir);
} else {
const struct cred *old_cred;
struct cred *override_cred;
err = -ENOMEM;
override_cred = prepare_creds();
if (!override_cred)
goto out_drop_write;
/*
* CAP_SYS_ADMIN for setting xattr on whiteout, opaque dir
* CAP_DAC_OVERRIDE for create in workdir, rename
* CAP_FOWNER for removing whiteout from sticky dir
* CAP_FSETID for chmod of opaque dir
* CAP_CHOWN for chown of opaque dir
*/
cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
cap_raise(override_cred->cap_effective, CAP_FOWNER);
cap_raise(override_cred->cap_effective, CAP_FSETID);
cap_raise(override_cred->cap_effective, CAP_CHOWN);
old_cred = override_creds(override_cred);
const struct cred *old_cred = ovl_override_creds(dentry->d_sb);
err = ovl_remove_and_whiteout(dentry, is_dir);
revert_creds(old_cred);
put_cred(override_cred);
}
out_drop_write:
ovl_drop_write(dentry);
@ -725,7 +689,6 @@ static int ovl_rename2(struct inode *olddir, struct dentry *old,
bool new_is_dir = false;
struct dentry *opaquedir = NULL;
const struct cred *old_cred = NULL;
struct cred *override_cred = NULL;
err = -EINVAL;
if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
@ -794,26 +757,8 @@ static int ovl_rename2(struct inode *olddir, struct dentry *old,
old_opaque = !OVL_TYPE_PURE_UPPER(old_type);
new_opaque = !OVL_TYPE_PURE_UPPER(new_type);
if (old_opaque || new_opaque) {
err = -ENOMEM;
override_cred = prepare_creds();
if (!override_cred)
goto out_drop_write;
/*
* CAP_SYS_ADMIN for setting xattr on whiteout, opaque dir
* CAP_DAC_OVERRIDE for create in workdir
* CAP_FOWNER for removing whiteout from sticky dir
* CAP_FSETID for chmod of opaque dir
* CAP_CHOWN for chown of opaque dir
*/
cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
cap_raise(override_cred->cap_effective, CAP_FOWNER);
cap_raise(override_cred->cap_effective, CAP_FSETID);
cap_raise(override_cred->cap_effective, CAP_CHOWN);
old_cred = override_creds(override_cred);
}
if (old_opaque || new_opaque)
old_cred = ovl_override_creds(old->d_sb);
if (overwrite && OVL_TYPE_MERGE_OR_LOWER(new_type) && new_is_dir) {
opaquedir = ovl_check_empty_and_clear(new);
@ -943,10 +888,8 @@ out_dput_old:
out_unlock:
unlock_rename(new_upperdir, old_upperdir);
out_revert_creds:
if (old_opaque || new_opaque) {
if (old_opaque || new_opaque)
revert_creds(old_cred);
put_cred(override_cred);
}
out_drop_write:
ovl_drop_write(old);
out:

1
fs/overlayfs/overlayfs.h
View File

@ -153,6 +153,7 @@ void ovl_drop_write(struct dentry *dentry);
bool ovl_dentry_is_opaque(struct dentry *dentry);
void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque);
bool ovl_is_whiteout(struct dentry *dentry);
const struct cred *ovl_override_creds(struct super_block *sb);
void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry);
struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags);

14
fs/overlayfs/readdir.c
View File

@ -36,6 +36,7 @@ struct ovl_dir_cache {
struct ovl_readdir_data {
struct dir_context ctx;
struct dentry *dentry;
bool is_lowest;
struct rb_root root;
struct list_head *list;
@ -206,17 +207,8 @@ static int ovl_check_whiteouts(struct dentry *dir, struct ovl_readdir_data *rdd)
struct ovl_cache_entry *p;
struct dentry *dentry;
const struct cred *old_cred;
struct cred *override_cred;
override_cred = prepare_creds();
if (!override_cred)
return -ENOMEM;
/*
* CAP_DAC_OVERRIDE for lookup
*/
cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
old_cred = override_creds(override_cred);
old_cred = ovl_override_creds(rdd->dentry->d_sb);
inode_lock(dir->d_inode);
err = 0;
@ -234,7 +226,6 @@ static int ovl_check_whiteouts(struct dentry *dir, struct ovl_readdir_data *rdd)
inode_unlock(dir->d_inode);
}
revert_creds(old_cred);
put_cred(override_cred);
return err;
}
@ -290,6 +281,7 @@ static int ovl_dir_read_merged(struct dentry *dentry, struct list_head *list)
struct path realpath;
struct ovl_readdir_data rdd = {
.ctx.actor = ovl_fill_merge,
.dentry = dentry,
.list = list,
.root = RB_ROOT,
.is_lowest = false,

37
fs/overlayfs/super.c
View File

@ -42,6 +42,8 @@ struct ovl_fs {
long lower_namelen;
/* pathnames of lower and upper dirs, for show_options */
struct ovl_config config;
/* creds of process who forced instantiation of super block */
const struct cred *creator_cred;
};
struct ovl_dir_cache;
@ -265,6 +267,13 @@ bool ovl_is_whiteout(struct dentry *dentry)
return inode && IS_WHITEOUT(inode);
}
const struct cred *ovl_override_creds(struct super_block *sb)
{
struct ovl_fs *ofs = sb->s_fs_info;
return override_creds(ofs->creator_cred);
}
static bool ovl_is_opaquedir(struct dentry *dentry)
{
int res;
@ -603,6 +612,7 @@ static void ovl_put_super(struct super_block *sb)
kfree(ufs->config.lowerdir);
kfree(ufs->config.upperdir);
kfree(ufs->config.workdir);
put_cred(ufs->creator_cred);
kfree(ufs);
}
@ -1064,16 +1074,19 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
/*
* Upper should support d_type, else whiteouts are visible.
* Given workdir and upper are on same fs, we can do
* iterate_dir() on workdir.
* iterate_dir() on workdir. This check requires successful
* creation of workdir in previous step.
*/
err = ovl_check_d_type_supported(&workpath);
if (err < 0)
goto out_put_workdir;
if (ufs->workdir) {
err = ovl_check_d_type_supported(&workpath);
if (err < 0)
goto out_put_workdir;
if (!err) {
pr_err("overlayfs: upper fs needs to support d_type.\n");
err = -EINVAL;
goto out_put_workdir;
if (!err) {
pr_err("overlayfs: upper fs needs to support d_type.\n");
err = -EINVAL;
goto out_put_workdir;
}
}
}
@ -1108,10 +1121,14 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
else
sb->s_d_op = &ovl_dentry_operations;
ufs->creator_cred = prepare_creds();
if (!ufs->creator_cred)
goto out_put_lower_mnt;
err = -ENOMEM;
oe = ovl_alloc_entry(numlower);
if (!oe)
goto out_put_lower_mnt;
goto out_put_cred;
root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, oe));
if (!root_dentry)
@ -1144,6 +1161,8 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
out_free_oe:
kfree(oe);
out_put_cred:
put_cred(ufs->creator_cred);
out_put_lower_mnt:
for (i = 0; i < ufs->numlower; i++)
mntput(ufs->lower_mnt[i]);