Messages in this thread | | | From | (Eric W. Biederman) | Subject | Re: [PATCH -mm 5/7] add user namespace | Date | Fri, 14 Jul 2006 11:36:27 -0600 |
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Dave Hansen <haveblue@us.ibm.com> writes:
> On Fri, 2006-07-14 at 12:08 -0500, Serge E. Hallyn wrote: >> yes, of course, vfsmount, which I assume is what Eric meant? >> >> Which means we'd have to do this at permission() using the nameidata, or >> pass nd to generic_permission. > > Yeah, I think so. But, this is well into Al territory, and there might > be a better way.
Well until we get that sorted out I will keep picking on i_sb.
The one thing that just occurred to me is that the generic permission should end up structured as below. I don't know if it is cheaper but it is certainly more obvious.
Eric
int generic_permission(struct inode *inode, int mask, int (*check_acl)(struct inode *inode, int mask)) { umode_t mode = inode->i_mode; + if (unlikely(current->nsproxy->user_ns != inode->i_sb->user_ns)) + goto unknown_user;
if (current->fsuid == inode->i_uid) 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)) mode >>= 3; } + unknown_user: /* * 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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