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vfs: Don't create inodes with a uid or gid unknown to the vfs

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It is expected that filesystems can not represent uids and gids from
outside of their user namespace.  Keep things simple by not even
trying to create filesystem nodes with non-sense uids and gids.

Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2016-07-01 12:52:06 -05:00
parent 0bd23d09b8
commit 036d523641
1 changed files with 8 additions and 2 deletions
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10
fs/namei.c
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@ -2814,16 +2814,22 @@ static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
* 1. We can't do it if child already exists (open has special treatment for * 1. We can't do it if child already exists (open has special treatment for
* this case, but since we are inlined it's OK) * this case, but since we are inlined it's OK)
* 2. We can't do it if dir is read-only (done in permission()) * 2. We can't do it if dir is read-only (done in permission())
* 3. We should have write and exec permissions on dir * 3. We can't do it if the fs can't represent the fsuid or fsgid.
* 4. We can't do it if dir is immutable (done in permission()) * 4. We should have write and exec permissions on dir
* 5. We can't do it if dir is immutable (done in permission())
*/ */
static inline int may_create(struct inode *dir, struct dentry *child) static inline int may_create(struct inode *dir, struct dentry *child)
{ {
struct user_namespace *s_user_ns;
audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE); audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
if (child->d_inode) if (child->d_inode)
return -EEXIST; return -EEXIST;
if (IS_DEADDIR(dir)) if (IS_DEADDIR(dir))
return -ENOENT; return -ENOENT;
s_user_ns = dir->i_sb->s_user_ns;
if (!kuid_has_mapping(s_user_ns, current_fsuid()) ||
!kgid_has_mapping(s_user_ns, current_fsgid()))
return -EOVERFLOW;
return inode_permission(dir, MAY_WRITE | MAY_EXEC); return inode_permission(dir, MAY_WRITE | MAY_EXEC);
} }