Date: Thu, 4 Jun 2015 13:25:19 +0530 (IST) From: P J P <ppandit@...hat.com> To: oss security list <oss-security@...ts.openwall.com> cc: cve-assign@...re.org, "Eric W. Biederman" <ebiederm@...ssion.com> Subject: Re: Re: CVE request Linux kernel: ns: user namespaces panic Hello Eric, +-- On Thu, 4 Jun 2015, Eric W. Biederman wrote --+ | The core issue is that a unprivileged user could call umount(MNT_DETACH) | and in the right circumstances gain access to every file on essentially | any filesystem in the mount namespace. ... | The bug fix modifies umount(MNT_DETACH) to keeps mounts covered | even after the actual umount. That changes makes it unsafe for | copy_tree to run on an unmounted mount tree because one of it's | assumptions is violated. Which assumption I do not remember at this | late hour. But I think it was something bad enough to cause a crash. | I can not recall all of the details when reading through the code | at this late hour. | | Previously copy_tree on an unmounted tree would just return a single | struct mount as all of the connections would have been cleanly removed. | | So I believe cd4a40174b71acd021877341684d8bb1dc8ea4ae prevents a | difficult to trigger crash if you have | e0c9c0afd2fc958ffa34b697972721d81df8a56f applied. | | e0c9c0afd2fc958ffa34b697972721d81df8a56f mnt: Update detach_mounts to leave mounts connected | is the real bug fix that fixes a fairly scary issue. | | I hope that helps. Yes, it does. Thank you so much for throwing light on the real issue and its corresponding fix. I appreciate it. Thank you. -- Prasad J Pandit / Red Hat Product Security Team 47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F
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