Date: Fri, 16 Apr 2021 16:53:50 +0200 From: Salvatore Bonaccorso <carnil@...ian.org> To: oss-security@...ts.openwall.com Subject: Re: [CVE-2021-3493] Ubuntu Linux kernel overlayfs fs caps privilege escalation Hi Steve, On Thu, Apr 15, 2021 at 02:31:14PM -0700, Steve Beattie wrote: > Hello, > > An independent security researcher reported via the SSD Secure > Disclosure program that the overlayfs stacking file system within the > Linux kernel as used within Ubuntu did not properly validate the > application of file capabilities against user namespaces. > > This issue is likely Ubuntu specific, as Ubuntu carries a patch to > enable unprivileged overlayfs mounts. The combination of that patch > plus allowing unprivileged user namespaces by default in Ubuntu allows > an unprivileged attacker to gain elevated privileges. > > A commit that addresses the issue was applied in the upstream kernel: > > 7c03e2cda4a5 ("vfs: move cap_convert_nscap() call into vfs_setxattr()") (v5.10) For completeness, this though was in v5.11-rc1 right? Regards, Salvatore
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