linux-kernel - Arithmetic overflow in may_expand

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <4AD75AE3.80803@agilent.com>
Date:	Thu, 15 Oct 2009 10:24:51 -0700
From:	Earl Chew <earl_chew@...lent.com>
To:	linux-kernel@...r.kernel.org
Subject: Arithmetic overflow in may_expand_vm()

This code currently reads:

> int may_expand_vm(struct mm_struct *mm, unsigned long npages)
> {
>         unsigned long cur = mm->total_vm;       /* pages */
>         unsigned long lim;
> 
>         lim = current->signal->rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
> 
>         if (cur + npages > lim)
>                 return 0;
>         return 1;
> }

If npages is stupendously large, the failure predicate may
return a false negative due to (cur + npages) overflowing and
wrapping.

I think it's more robustly written as:

          if (npages > lim - cur)
                  return 0;



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/