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Revert "FROMLIST: overlayfs: override_creds=off option bypass cr..."

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Revert submission 1881578

Reason for revert: broken build in CI
Reverted Changes:
Id2c6fa6ee:FROMLIST: Add flags option to get xattr method pai...
Ifa966dabd:FROMLIST: overlayfs: inode_owner_or_capable called...
I46e6c74ff:FROMLIST: overlayfs: override_creds=off option byp...
I0b8fe9f1f:FROMLIST: overlayfs: handle XATTR_NOSECURITY flag ...

Change-Id: Ib78cfc2cfb717a0c4a1997399aaa47d38c6f366d
Signed-off-by: David Anderson <dvander@google.com>
This commit is contained in:
David Anderson
2021-11-19 18:00:53 +00:00
parent c100cf8c92
commit 650b7fa416
11 changed files with 42 additions and 100 deletions
Download Patch File Download Diff File Expand all files Collapse all files

26
Documentation/filesystems/overlayfs.rst
View File

@@ -195,7 +195,7 @@ handle it in two different ways:
1. return EXDEV error: this error is returned by rename(2) when trying to
move a file or directory across filesystem boundaries. Hence
applications are usually prepared to handle this error (mv(1) for example
applications are usually prepared to hande this error (mv(1) for example
recursively copies the directory tree). This is the default behavior.
2. If the "redirect_dir" feature is enabled, then the directory will be
@@ -324,30 +324,6 @@ and
The resulting access permissions should be the same. The difference is in
the time of copy (on-demand vs. up-front).
### Non overlapping credentials
As noted above, all access to the upper, lower and work directories is the
recorded mounter's MAC and DAC credentials. The incoming accesses are
checked against the caller's credentials.
In the case where caller MAC or DAC credentials do not overlap the mounter, a
use case available in older versions of the driver, the override_creds mount
flag can be turned off. For when the use pattern has caller with legitimate
credentials where the mounter does not. For example init may have been the
mounter, but the caller would have execute or read MAC permissions where
init would not. override_creds off means all access, incoming, upper, lower
or working, will be tested against the caller.
Several unintended side effects will occur though. The caller without certain
key capabilities or lower privilege will not always be able to delete files or
directories, create nodes, or search some restricted directories. The ability
to search and read a directory entry is spotty as a result of the cache
mechanism not re-testing the credentials because of the assumption, a
privileged caller can fill cache, then a lower privilege can read the directory
cache. The uneven security model where cache, upperdir and workdir are opened
at privilege, but accessed without creating a form of privilege escalation,
should only be used with strict understanding of the side effects and of the
security policies.
Multiple lower layers
---------------------

2
fs/overlayfs/copy_up.c
View File

@@ -1032,7 +1032,7 @@ static int ovl_copy_up_flags(struct dentry *dentry, int flags)
dput(parent);
dput(next);
}
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
return err;
}

17
fs/overlayfs/dir.c
View File

@@ -570,7 +570,7 @@ static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
struct ovl_cattr *attr, bool origin)
{
int err;
const struct cred *old_cred, *hold_cred = NULL;
const struct cred *old_cred;
struct cred *override_cred;
struct dentry *parent = dentry->d_parent;
@@ -597,15 +597,14 @@ static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
override_cred->fsgid = inode->i_gid;
if (!attr->hardlink) {
err = security_dentry_create_files_as(dentry,
attr->mode, &dentry->d_name,
old_cred ? old_cred : current_cred(),
attr->mode, &dentry->d_name, old_cred,
override_cred);
if (err) {
put_cred(override_cred);
goto out_revert_creds;
}
}
hold_cred = override_creds(override_cred);
put_cred(override_creds(override_cred));
put_cred(override_cred);
if (!ovl_dentry_is_whiteout(dentry))
@@ -614,9 +613,7 @@ static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
err = ovl_create_over_whiteout(dentry, inode, attr);
}
out_revert_creds:
ovl_revert_creds(dentry->d_sb, old_cred ?: hold_cred);
if (old_cred && hold_cred)
put_cred(hold_cred);
revert_creds(old_cred);
return err;
}
@@ -693,7 +690,7 @@ static int ovl_set_link_redirect(struct dentry *dentry)
old_cred = ovl_override_creds(dentry->d_sb);
err = ovl_set_redirect(dentry, false);
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
return err;
}
@@ -912,7 +909,7 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir)
err = ovl_remove_upper(dentry, is_dir, &list);
else
err = ovl_remove_and_whiteout(dentry, &list);
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
if (!err) {
if (is_dir)
clear_nlink(dentry->d_inode);
@@ -1287,7 +1284,7 @@ out_dput_old:
out_unlock:
unlock_rename(new_upperdir, old_upperdir);
out_revert_creds:
ovl_revert_creds(old->d_sb, old_cred);
revert_creds(old_cred);
if (update_nlink)
ovl_nlink_end(new);
out_drop_write:

22
fs/overlayfs/file.c
View File

@@ -63,7 +63,7 @@ static struct file *ovl_open_realfile(const struct file *file,
realfile = open_with_fake_path(&file->f_path, flags, realinode,
current_cred());
}
ovl_revert_creds(inode->i_sb, old_cred);
revert_creds(old_cred);
pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
file, file, ovl_whatisit(inode, realinode), file->f_flags,
@@ -207,7 +207,7 @@ static loff_t ovl_llseek(struct file *file, loff_t offset, int whence)
old_cred = ovl_override_creds(inode->i_sb);
ret = vfs_llseek(real.file, offset, whence);
ovl_revert_creds(inode->i_sb, old_cred);
revert_creds(old_cred);
file->f_pos = real.file->f_pos;
ovl_inode_unlock(inode);
@@ -321,7 +321,7 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
ovl_aio_cleanup_handler(aio_req);
}
out:
ovl_revert_creds(file_inode(file)->i_sb, old_cred);
revert_creds(old_cred);
ovl_file_accessed(file);
out_fdput:
fdput(real);
@@ -394,7 +394,7 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
ovl_aio_cleanup_handler(aio_req);
}
out:
ovl_revert_creds(file_inode(file)->i_sb, old_cred);
revert_creds(old_cred);
out_fdput:
fdput(real);
@@ -440,7 +440,7 @@ static ssize_t ovl_splice_write(struct pipe_inode_info *pipe, struct file *out,
file_end_write(real.file);
/* Update size */
ovl_copyattr(realinode, inode);
ovl_revert_creds(inode->i_sb, old_cred);
revert_creds(old_cred);
fdput(real);
out_unlock:
@@ -467,7 +467,7 @@ static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
if (file_inode(real.file) == ovl_inode_upper(file_inode(file))) {
old_cred = ovl_override_creds(file_inode(file)->i_sb);
ret = vfs_fsync_range(real.file, start, end, datasync);
ovl_revert_creds(file_inode(file)->i_sb, old_cred);
revert_creds(old_cred);
}
fdput(real);
@@ -491,7 +491,7 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
old_cred = ovl_override_creds(file_inode(file)->i_sb);
ret = call_mmap(vma->vm_file, vma);
ovl_revert_creds(file_inode(file)->i_sb, old_cred);
revert_creds(old_cred);
ovl_file_accessed(file);
return ret;
@@ -510,7 +510,7 @@ static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len
old_cred = ovl_override_creds(file_inode(file)->i_sb);
ret = vfs_fallocate(real.file, mode, offset, len);
ovl_revert_creds(file_inode(file)->i_sb, old_cred);
revert_creds(old_cred);
/* Update size */
ovl_copyattr(ovl_inode_real(inode), inode);
@@ -532,7 +532,7 @@ static int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
old_cred = ovl_override_creds(file_inode(file)->i_sb);
ret = vfs_fadvise(real.file, offset, len, advice);
ovl_revert_creds(file_inode(file)->i_sb, old_cred);
revert_creds(old_cred);
fdput(real);
@@ -582,7 +582,7 @@ static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
flags);
break;
}
ovl_revert_creds(file_inode(file_out)->i_sb, old_cred);
revert_creds(old_cred);
/* Update size */
ovl_copyattr(ovl_inode_real(inode_out), inode_out);
@@ -641,7 +641,7 @@ static int ovl_flush(struct file *file, fl_owner_t id)
if (real.file->f_op->flush) {
old_cred = ovl_override_creds(file_inode(file)->i_sb);
err = real.file->f_op->flush(real.file, id);
ovl_revert_creds(file_inode(file)->i_sb, old_cred);
revert_creds(old_cred);
}
fdput(real);

24
fs/overlayfs/inode.c
View File

@@ -78,7 +78,7 @@ int ovl_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
inode_lock(upperdentry->d_inode);
old_cred = ovl_override_creds(dentry->d_sb);
err = notify_change(&init_user_ns, upperdentry, attr, NULL);
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
if (!err)
ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
inode_unlock(upperdentry->d_inode);
@@ -270,7 +270,7 @@ int ovl_getattr(struct user_namespace *mnt_userns, const struct path *path,
stat->nlink = dentry->d_inode->i_nlink;
out:
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
return err;
}
@@ -305,7 +305,7 @@ int ovl_permission(struct user_namespace *mnt_userns,
mask |= MAY_READ;
}
err = inode_permission(&init_user_ns, realinode, mask);
ovl_revert_creds(inode->i_sb, old_cred);
revert_creds(old_cred);
return err;
}
@@ -322,7 +322,7 @@ static const char *ovl_get_link(struct dentry *dentry,
old_cred = ovl_override_creds(dentry->d_sb);
p = vfs_get_link(ovl_dentry_real(dentry), done);
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
return p;
}
@@ -353,7 +353,7 @@ int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
if (!value && !upperdentry) {
old_cred = ovl_override_creds(dentry->d_sb);
err = vfs_getxattr(&init_user_ns, realdentry, name, NULL, 0);
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
if (err < 0)
goto out_drop_write;
}
@@ -374,7 +374,7 @@ int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
WARN_ON(flags != XATTR_REPLACE);
err = vfs_removexattr(&init_user_ns, realdentry, name);
}
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
/* copy c/mtime */
ovl_copyattr(d_inode(realdentry), inode);
@@ -396,7 +396,7 @@ int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
old_cred = ovl_override_creds(dentry->d_sb);
res = __vfs_getxattr(&init_user_ns, realdentry, d_inode(realdentry),
name, value, size, flags);
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
return res;
}
@@ -424,7 +424,7 @@ ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
old_cred = ovl_override_creds(dentry->d_sb);
res = vfs_listxattr(realdentry, list, size);
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
if (res <= 0 || size == 0)
return res;
@@ -462,7 +462,7 @@ struct posix_acl *ovl_get_acl(struct inode *inode, int type, bool rcu)
old_cred = ovl_override_creds(inode->i_sb);
acl = get_acl(realinode, type);
ovl_revert_creds(inode->i_sb, old_cred);
revert_creds(old_cred);
return acl;
}
@@ -496,7 +496,7 @@ static int ovl_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
old_cred = ovl_override_creds(inode->i_sb);
err = realinode->i_op->fiemap(realinode, fieinfo, start, len);
ovl_revert_creds(inode->i_sb, old_cred);
revert_creds(old_cred);
return err;
}
@@ -567,7 +567,7 @@ int ovl_fileattr_set(struct user_namespace *mnt_userns,
err = ovl_set_protattr(inode, upperpath.dentry, fa);
if (!err)
err = ovl_real_fileattr_set(&upperpath, fa);
ovl_revert_creds(inode->i_sb, old_cred);
revert_creds(old_cred);
/*
* Merge real inode flags with inode flags read from
@@ -629,7 +629,7 @@ int ovl_fileattr_get(struct dentry *dentry, struct fileattr *fa)
old_cred = ovl_override_creds(inode->i_sb);
err = ovl_real_fileattr_get(&realpath, fa);
ovl_fileattr_prot_flags(inode, fa);
ovl_revert_creds(inode->i_sb, old_cred);
revert_creds(old_cred);
return err;
}

6
fs/overlayfs/namei.c
View File

@@ -1106,7 +1106,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
ovl_dentry_update_reval(dentry, upperdentry,
DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE);
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
if (origin_path) {
dput(origin_path->dentry);
kfree(origin_path);
@@ -1133,7 +1133,7 @@ out_put_upper:
kfree(upperredirect);
out:
kfree(d.redirect);
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
return ERR_PTR(err);
}
@@ -1185,7 +1185,7 @@ bool ovl_lower_positive(struct dentry *dentry)
dput(this);
}
}
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
return positive;
}

1
fs/overlayfs/overlayfs.h
View File

@@ -282,7 +282,6 @@ int ovl_want_write(struct dentry *dentry);
void ovl_drop_write(struct dentry *dentry);
struct dentry *ovl_workdir(struct dentry *dentry);
const struct cred *ovl_override_creds(struct super_block *sb);
void ovl_revert_creds(struct super_block *sb, const struct cred *oldcred);
int ovl_can_decode_fh(struct super_block *sb);
struct dentry *ovl_indexdir(struct super_block *sb);
bool ovl_index_all(struct super_block *sb);

1
fs/overlayfs/ovl_entry.h
View File

@@ -20,7 +20,6 @@ struct ovl_config {
bool metacopy;
bool userxattr;
bool ovl_volatile;
bool override_creds;
};
struct ovl_sb {

8
fs/overlayfs/readdir.c
View File

@@ -286,7 +286,7 @@ static int ovl_check_whiteouts(struct dentry *dir, struct ovl_readdir_data *rdd)
}
inode_unlock(dir->d_inode);
}
ovl_revert_creds(rdd->dentry->d_sb, old_cred);
revert_creds(old_cred);
return err;
}
@@ -789,7 +789,7 @@ static int ovl_iterate(struct file *file, struct dir_context *ctx)
}
err = 0;
out:
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
return err;
}
@@ -841,7 +841,7 @@ static struct file *ovl_dir_open_realfile(const struct file *file,
old_cred = ovl_override_creds(file_inode(file)->i_sb);
res = ovl_path_open(realpath, O_RDONLY | (file->f_flags & O_LARGEFILE));
ovl_revert_creds(file_inode(file)->i_sb, old_cred);
revert_creds(old_cred);
return res;
}
@@ -967,7 +967,7 @@ int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list)
old_cred = ovl_override_creds(dentry->d_sb);
err = ovl_dir_read_merged(dentry, list, &root);
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
if (err)
return err;

22
fs/overlayfs/super.c
View File

@@ -53,11 +53,6 @@ module_param_named(xino_auto, ovl_xino_auto_def, bool, 0644);
MODULE_PARM_DESC(xino_auto,
"Auto enable xino feature");
static bool __read_mostly ovl_override_creds_def = true;
module_param_named(override_creds, ovl_override_creds_def, bool, 0644);
MODULE_PARM_DESC(ovl_override_creds_def,
"Use mounter's credentials for accesses");
static void ovl_entry_stack_free(struct ovl_entry *oe)
{
unsigned int i;
@@ -387,9 +382,6 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
seq_puts(m, ",volatile");
if (ofs->config.userxattr)
seq_puts(m, ",userxattr");
if (ofs->config.override_creds != ovl_override_creds_def)
seq_show_option(m, "override_creds",
ofs->config.override_creds ? "on" : "off");
return 0;
}
@@ -445,8 +437,6 @@ enum {
OPT_METACOPY_ON,
OPT_METACOPY_OFF,
OPT_VOLATILE,
OPT_OVERRIDE_CREDS_ON,
OPT_OVERRIDE_CREDS_OFF,
OPT_ERR,
};
@@ -469,8 +459,6 @@ static const match_table_t ovl_tokens = {
{OPT_METACOPY_ON, "metacopy=on"},
{OPT_METACOPY_OFF, "metacopy=off"},
{OPT_VOLATILE, "volatile"},
{OPT_OVERRIDE_CREDS_ON, "override_creds=on"},
{OPT_OVERRIDE_CREDS_OFF, "override_creds=off"},
{OPT_ERR, NULL}
};
@@ -530,7 +518,6 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
if (!config->redirect_mode)
return -ENOMEM;
config->override_creds = ovl_override_creds_def;
while ((p = ovl_next_opt(&opt)) != NULL) {
int token;
@@ -632,14 +619,6 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
config->userxattr = true;
break;
case OPT_OVERRIDE_CREDS_ON:
config->override_creds = true;
break;
case OPT_OVERRIDE_CREDS_OFF:
config->override_creds = false;
break;
default:
pr_err("unrecognized mount option \"%s\" or missing value\n",
p);
@@ -2161,6 +2140,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
kfree(splitlower);
sb->s_root = root_dentry;
return 0;
out_free_oe:

13
fs/overlayfs/util.c
View File

@@ -38,18 +38,9 @@ const struct cred *ovl_override_creds(struct super_block *sb)
{
struct ovl_fs *ofs = sb->s_fs_info;
if (!ofs->config.override_creds)
return NULL;
return override_creds(ofs->creator_cred);
}
void ovl_revert_creds(struct super_block *sb, const struct cred *old_cred)
{
if (old_cred)
revert_creds(old_cred);
}
/*
* Check if underlying fs supports file handles and try to determine encoding
* type, in order to deduce maximum inode number used by fs.
@@ -908,7 +899,7 @@ int ovl_nlink_start(struct dentry *dentry)
* value relative to the upper inode nlink in an upper inode xattr.
*/
err = ovl_set_nlink_upper(dentry);
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
out:
if (err)
@@ -926,7 +917,7 @@ void ovl_nlink_end(struct dentry *dentry)
old_cred = ovl_override_creds(dentry->d_sb);
ovl_cleanup_index(dentry);
ovl_revert_creds(dentry->d_sb, old_cred);
revert_creds(old_cred);
}
ovl_inode_unlock(inode);