Messages in this thread | | | From | (Eric W. Biederman) | Subject | Re: [PATCH -mm 5/7] add user namespace | Date | Fri, 14 Jul 2006 10:49:52 -0600 |
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"Serge E. Hallyn" <serue@us.ibm.com> writes:
> Quoting Eric W. Biederman (ebiederm@xmission.com): >> Dave Hansen <haveblue@us.ibm.com> writes: >> >> > On Thu, 2006-07-13 at 21:45 -0600, Eric W. Biederman wrote: >> >> I think for filesystems like /proc and /sys that there will normally >> >> be problems. However many of those problems can be rationalized away >> >> as a reasonable optimization, or are not immediately apparent. >> > >> > Could you talk about some of these problems? >> >> Already mentioned but. rw permissions on sensitive files are for >> uid == 0. No capability checks are performed. > > As Herbert (IIRC) pointed out that could/should be fixed.
Capabilities have always fitted badly in with the normal unix permissions. So if we have a solution that works nicely with normal unix permissions we will have a nice general solution, that is easy for people to understand.
What I am talking about is making a small tweak to the permission checking as below. Why do you keep avoiding even considering it?
Eric
int generic_permission(struct inode *inode, int mask, int (*check_acl)(struct inode *inode, int mask)) { umode_t mode = inode->i_mode; - if (current->fsuid == inode->i_uid) + if ((current->fsuid == inode->i_uid) && + (current->nsproxy->user_ns == inode->i_sb->user_ns)) mode >>= 6; else { if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) { int error = check_acl(inode, mask); if (error == -EACCES) goto check_capabilities; else if (error != -EAGAIN) return error; } - if (in_group_p(inode->i_gid)) + if (in_group_p(inode->i_sb->user_ns, inode->i_gid)) mode >>= 3; } /* * If the DACs are ok we don't need any capability check. */ if (((mode & mask & (MAY_READ|MAY_WRITE|MAY_EXEC)) == mask)) return 0; check_capabilities: /* * Read/write DACs are always overridable. * Executable DACs are overridable if at least one exec bit is set. */ if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO) || S_ISDIR(inode->i_mode)) if (capable(CAP_DAC_OVERRIDE)) return 0; /* * Searching includes executable on directories, else just read. */ if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE))) if (capable(CAP_DAC_READ_SEARCH)) return 0; return -EACCES; }
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