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userns: userns: check user namespace for task->file uid equivalence checks

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Cheat for now and say all files belong to init_user_ns.  Next step will be
to let superblocks belong to a user_ns, and derive inode_userns(inode)
from inode->i_sb->s_user_ns.  Finally we'll introduce more flexible
arrangements.

Changelog:
	Feb 15: make is_owner_or_cap take const struct inode
	Feb 23: make is_owner_or_cap bool

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Daniel Lezcano <daniel.lezcano@free.fr>
Acked-by: David Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Serge E. Hallyn 2011-03-23 16:43:25 -07:00 committed by Linus Torvalds
parent b0e77598f8
commit e795b71799
3 changed files with 40 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

17
fs/inode.c
View file

@ -25,6 +25,7 @@
#include <linux/async.h>
#include <linux/posix_acl.h>
#include <linux/ima.h>
#include <linux/cred.h>
/*
* This is needed for the following functions:
@ -1733,3 +1734,19 @@ void inode_init_owner(struct inode *inode, const struct inode *dir,
inode->i_mode = mode;
}
EXPORT_SYMBOL(inode_init_owner);
/*
* return true if current either has CAP_FOWNER to the
* file, or owns the file.
*/
bool is_owner_or_cap(const struct inode *inode)
{
struct user_namespace *ns = inode_userns(inode);
if (current_user_ns() == ns && current_fsuid() == inode->i_uid)
return true;
if (ns_capable(ns, CAP_FOWNER))
return true;
return false;
}
EXPORT_SYMBOL(is_owner_or_cap);

21
fs/namei.c
View file

@ -183,6 +183,9 @@ static int acl_permission_check(struct inode *inode, int mask, unsigned int flag
mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
if (current_user_ns() != inode_userns(inode))
goto other_perms;
if (current_fsuid() == inode->i_uid)
mode >>= 6;
else {
@ -196,6 +199,7 @@ static int acl_permission_check(struct inode *inode, int mask, unsigned int flag
mode >>= 3;
}
other_perms:
/*
* If the DACs are ok we don't need any capability check.
*/
@ -237,7 +241,7 @@ int generic_permission(struct inode *inode, int mask, unsigned int flags,
* Executable DACs are overridable if at least one exec bit is set.
*/
if (!(mask & MAY_EXEC) || execute_ok(inode))
if (capable(CAP_DAC_OVERRIDE))
if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE))
return 0;
/*
@ -245,7 +249,7 @@ int generic_permission(struct inode *inode, int mask, unsigned int flags,
*/
mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
if (capable(CAP_DAC_READ_SEARCH))
if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH))
return 0;
return -EACCES;
@ -654,6 +658,7 @@ static inline int handle_reval_path(struct nameidata *nd)
static inline int exec_permission(struct inode *inode, unsigned int flags)
{
int ret;
struct user_namespace *ns = inode_userns(inode);
if (inode->i_op->permission) {
ret = inode->i_op->permission(inode, MAY_EXEC, flags);
@ -666,7 +671,8 @@ static inline int exec_permission(struct inode *inode, unsigned int flags)
if (ret == -ECHILD)
return ret;
if (capable(CAP_DAC_OVERRIDE) || capable(CAP_DAC_READ_SEARCH))
if (ns_capable(ns, CAP_DAC_OVERRIDE) ||
ns_capable(ns, CAP_DAC_READ_SEARCH))
goto ok;
return ret;
@ -1842,11 +1848,15 @@ static inline int check_sticky(struct inode *dir, struct inode *inode)
if (!(dir->i_mode & S_ISVTX))
return 0;
if (current_user_ns() != inode_userns(inode))
goto other_userns;
if (inode->i_uid == fsuid)
return 0;
if (dir->i_uid == fsuid)
return 0;
return !capable(CAP_FOWNER);
other_userns:
return !ns_capable(inode_userns(inode), CAP_FOWNER);
}
/*
@ -2440,7 +2450,8 @@ int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
if (error)
return error;
if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
if ((S_ISCHR(mode) || S_ISBLK(mode)) &&
!ns_capable(inode_userns(dir), CAP_MKNOD))
return -EPERM;
if (!dir->i_op->mknod)

9
include/linux/fs.h
View file

@ -1457,8 +1457,13 @@ enum {
#define put_fs_excl() atomic_dec(&current->fs_excl)
#define has_fs_excl() atomic_read(&current->fs_excl)
#define is_owner_or_cap(inode) \
((current_fsuid() == (inode)->i_uid) || capable(CAP_FOWNER))
/*
* until VFS tracks user namespaces for inodes, just make all files
* belong to init_user_ns
*/
extern struct user_namespace init_user_ns;
#define inode_userns(inode) (&init_user_ns)
extern bool is_owner_or_cap(const struct inode *inode);
/* not quite ready to be deprecated, but... */
extern void lock_super(struct super_block *);