From: Paul Moore <firstname.lastname@example.org> To: "H.J. Lu" <email@example.com>, "H. Peter Anvin" <firstname.lastname@example.org>, email@example.com Cc: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com Subject: Re: [PATCH] x86: remove the x32 syscall bitmask from syscall_get_nr() Date: Mon, 25 Mar 2013 16:55:17 -0400 [thread overview] Message-ID: <1729301.D1jGz2qpIc@sifl> (raw) In-Reply-To: <CAMe9rOriYUYVmef36PVuZn5LWtthryj3n7vRzXRObC_ZkcVuqQ@mail.gmail.com> On Friday, March 15, 2013 03:18:12 PM H.J. Lu wrote: > On Fri, Mar 15, 2013 at 2:56 PM, H. Peter Anvin <firstname.lastname@example.org> wrote: > > On 03/15/2013 02:15 PM, Paul Moore wrote: > >> On Tuesday, February 26, 2013 03:58:23 PM Paul Moore wrote: > >>> On Friday, February 15, 2013 12:21:43 PM Paul Moore wrote: > >>>> Commit fca460f95e928bae373daa8295877b6905bc62b8 simplified the x32 > >>>> implementation by creating a syscall bitmask, equal to 0x40000000, that > >>>> could be applied to x32 syscalls such that the masked syscall number > >>>> would be the same as a x86_64 syscall. While that patch was a nice > >>>> way to simplify the code, it went a bit too far by adding the mask to > >>>> syscall_get_nr(); returning the masked syscall numbers can cause > >>>> confusion with callers that expect syscall numbers matching the x32 > >>>> ABI, e.g. unmasked syscall numbers. > >>>> > >>>> This patch fixes this by simply removing the mask from syscall_get_nr() > >>>> while preserving the other changes from the original commit. While > >>>> there are several syscall_get_nr() callers in the kernel, most simply > >>>> check that the syscall number is greater than zero, in this case this > >>>> patch will have no effect. Of those remaining callers, they appear > >>>> to be few, seccomp and ftrace, and from my testing of seccomp without > >>>> this patch the original commit definitely breaks things; the seccomp > >>>> filter does not correctly filter the syscalls due to the difference in > >>>> syscall numbers in the BPF filter and the value from syscall_get_nr(). > >>>> Applying this patch restores the seccomp BPF filter functionality on > >>>> x32. > >>>> > >>>> I've tested this patch with the seccomp BPF filters as well as ftrace > >>>> and everything looks reasonable to me; needless to say general usage > >>>> seemed fine as well. > >>> > >>> I just wanted to check and see where things stood with this patch. I'm > >>> not > >>> overly concerned about how this problem is solved, just that it is > >>> solved. > >>> If someone else has a better approach that is fine with me; I'll even > >>> make > >>> the offer to do additional testing if needed. > >> > >> Anyone? The seccomp filter bits are completely broken on x32 and I'd > >> like to get this fixed, if not with this patch then something else - I'm > >> more than happy to test/verify/etc whatever solution is deemed best ... > > > > Seems good to me -- H.J., do you seen any problem with this? > > It looks OK to me. Great, any chance of getting this fix merged for 3.9? -- paul moore security and virtualization @ redhat
next prev parent reply other threads:[~2013-03-25 20:55 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-02-15 17:21 Paul Moore 2013-02-15 19:02 ` H. Peter Anvin 2013-02-15 20:52 ` Paul Moore 2013-02-26 20:58 ` Paul Moore 2013-03-15 21:15 ` Paul Moore 2013-03-15 21:56 ` H. Peter Anvin 2013-03-15 22:18 ` H.J. Lu 2013-03-25 20:55 ` Paul Moore [this message] 2013-04-02 21:31 ` Paul Moore 2013-04-03 0:17 ` [tip:x86/urgent] " tip-bot for Paul Moore
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