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Message-ID: <CALCETrUXeBSv6KbsPC+kHTAbAB2B8T3rk5N-OOZvCPU8fOr5Ew@mail.gmail.com> Date: Fri, 15 Aug 2014 12:32:41 -0700 From: Andy Lutomirski <luto@...capital.net> To: Alexei Starovoitov <ast@...mgrid.com> Cc: "David S. Miller" <davem@...emloft.net>, Ingo Molnar <mingo@...nel.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Steven Rostedt <rostedt@...dmis.org>, Daniel Borkmann <dborkman@...hat.com>, Chema Gonzalez <chema@...gle.com>, Eric Dumazet <edumazet@...gle.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, "H. Peter Anvin" <hpa@...or.com>, Andrew Morton <akpm@...ux-foundation.org>, Kees Cook <keescook@...omium.org>, Linux API <linux-api@...r.kernel.org>, Network Development <netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH RFC v4 net-next 17/26] tracing: allow eBPF programs to be attached to events On Fri, Aug 15, 2014 at 12:29 PM, Alexei Starovoitov <ast@...mgrid.com> wrote: > On Fri, Aug 15, 2014 at 12:20 PM, Andy Lutomirski <luto@...capital.net> wrote: >>>> >>>> I don't think that fixing this should be a prerequisite for merging, >>>> since the risk is so small. Nonetheless, it would be nice. (This >>>> family of attacks has lead to several root vulnerabilities in the >>>> past.) >>> >>> Ok. I think keeping a track of pid between open and write is kinda >>> ugly. >> >> Agreed. >> >> TBH, I would just add a comment to the open implementation saying >> that, if unprivileged or less privileged open is allowed, then this >> needs to be fixed. > > ok. will do. > >>> Should we add some new CAP flag and check it for all file >>> ops? Another option is to conditionally make open() of tracing >>> files as cloexec... >> >> That won't help. The same attack can be done with SCM_RIGHTS, and >> cloexec can be cleared. > > ouch, can we then make ebpf FDs and may be debugfs FDs > not passable at all? Otherwise it feels that generality and > flexibility of FDs is becoming a burden. I'm not sure there's much of a general problem. The issue is when there's an fd for which write(2) (or other assumed-to-not-check-permissions calls like read, pread, pwrite, etc) depend on context. This is historically an issue for netlink and various /proc files. --Andy -- 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/
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