Date: Tue, 18 Jan 2022 18:57:57 +0000 From: John Haxby <john.haxby@...cle.com> To: "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com> CC: "jamie@...l-daniel.co.uk" <jamie@...l-daniel.co.uk>, "g@....io" <g@....io>, "misetichrvoje@...il.com" <misetichrvoje@...il.com>, "alecthechop@...il.com" <alecthechop@...il.com>, "isaac.badipe@...il.com" <isaac.badipe@...il.com> Subject: Re: Linux kernel: Heap buffer overflow in fs_context.c since version 5.1 > On 18 Jan 2022, at 18:21, Will <willsroot@...tonmail.com> wrote: > > There is a heap overflow bug in legacy_parse_param in which the length of data copied can be incremented beyond the width of the 1-page slab allocated for it. We currently have created functional LPE exploits against Ubuntu 20.04 and container escape exploits against Google's hardened COS. The bug was introduced in 5.1-rc1 (https://github.com/torvalds/linux/commit/3e1aeb00e6d132efc151dacc062b38269bc9eccc#diff-c4a9ea83de4a42a0d1bcbaf1f03ce35188f38da4987e0e7a52aae7f04de14a05) and is present in all Linux releases since. As of January 18th, this patch (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=722d94847de29310e8aa03fcbdb41fc92c521756) fixes this issue. > > The bug is caused by an integer underflow present in fs/fs_context.c:legacy_parse_param, which results in miscalculation of a valid max length. A bounds check is present at fs_context.c:551, returning an error if (len > PAGE_SIZE - 2 - size); however, if the value of size is greater than or equal to 4095, the unsigned subtraction will underflow to a massive value greater than len, so the check will not trigger. After this, the attacker may freely write data out-of-bounds. Changing the check to size + len + 2 > PAGE_SIZE (which the patch did) would fix this. > > Exploitation relies on the CAP_SYS_ADMIN capability; however, the permission only needs to be granted in the current namespace. An unprivileged user can use unshare(CLONE_NEWNS|CLONE_NEWUSER) to enter a namespace with the CAP_SYS_ADMIN permission, and then proceed with exploitation to root the system. This is CVE-2022-0185 jch Download attachment "signature.asc" of type "application/pgp-signature" (269 bytes)
Powered by blists - more mailing lists
Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.