From: Peter Zijlstra <peterz@infradead.org> To: Andrei Vagin <avagin@gmail.com> Cc: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, linux-um@lists.infradead.org, criu@openvz.org, avagin@google.com, Andrew Morton <akpm@linux-foundation.org>, Andy Lutomirski <luto@kernel.org>, Anton Ivanov <anton.ivanov@cambridgegreys.com>, Christian Brauner <christian.brauner@ubuntu.com>, Dmitry Safonov <0x7f454c46@gmail.com>, Ingo Molnar <mingo@redhat.com>, Jeff Dike <jdike@addtoit.com>, Mike Rapoport <rppt@linux.ibm.com>, Michael Kerrisk <mtk.manpages@gmail.com>, Oleg Nesterov <oleg@redhat.com>, Richard Weinberger <richard@nod.at>, Thomas Gleixner <tglx@linutronix.de> Subject: Re: [PATCH 2/4] arch/x86: implement the process_vm_exec syscall Date: Fri, 2 Jul 2021 10:51:13 +0200 [thread overview] Message-ID: <YN7TgV9RDJTRaY8R@hirez.programming.kicks-ass.net> (raw) In-Reply-To: <20210414055217.543246-3-avagin@gmail.com> I'm terrified of all of this... On Tue, Apr 13, 2021 at 10:52:15PM -0700, Andrei Vagin wrote: > +long swap_vm_exec_context(struct sigcontext __user *uctx) > +{ > + struct sigcontext ctx = {}; > + sigset_t set = {}; > + > + > + if (copy_from_user(&ctx, uctx, CONTEXT_COPY_SIZE)) > + return -EFAULT; > + /* A floating point state is managed from user-space. */ > + if (ctx.fpstate != 0) > + return -EINVAL; > + if (!user_access_begin(uctx, sizeof(*uctx))) > + return -EFAULT; > + unsafe_put_sigcontext(uctx, NULL, current_pt_regs(), (&set), Efault); > + user_access_end(); But here you save the sigcontext without FPU state. > + > + if (__restore_sigcontext(current_pt_regs(), &ctx, 0)) > + goto badframe; And here you restore sigcontext, *with* FPU state. At which point your FPU state is irrecoverably lost. Also, I'm not at all convinced this can ever do the right thing when the tasks don't agree on what the FPU state is. I suppose in the best case the save will EFAULT. > + > + return 0; > +Efault: > + user_access_end(); > +badframe: > + signal_fault(current_pt_regs(), uctx, "swap_vm_exec_context"); > + return -EFAULT; > +}
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org> To: Andrei Vagin <avagin@gmail.com> Cc: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, linux-um@lists.infradead.org, criu@openvz.org, avagin@google.com, Andrew Morton <akpm@linux-foundation.org>, Andy Lutomirski <luto@kernel.org>, Anton Ivanov <anton.ivanov@cambridgegreys.com>, Christian Brauner <christian.brauner@ubuntu.com>, Dmitry Safonov <0x7f454c46@gmail.com>, Ingo Molnar <mingo@redhat.com>, Jeff Dike <jdike@addtoit.com>, Mike Rapoport <rppt@linux.ibm.com>, Michael Kerrisk <mtk.manpages@gmail.com>, Oleg Nesterov <oleg@redhat.com>, Richard Weinberger <richard@nod.at>, Thomas Gleixner <tglx@linutronix.de> Subject: Re: [PATCH 2/4] arch/x86: implement the process_vm_exec syscall Date: Fri, 2 Jul 2021 10:51:13 +0200 [thread overview] Message-ID: <YN7TgV9RDJTRaY8R@hirez.programming.kicks-ass.net> (raw) In-Reply-To: <20210414055217.543246-3-avagin@gmail.com> I'm terrified of all of this... On Tue, Apr 13, 2021 at 10:52:15PM -0700, Andrei Vagin wrote: > +long swap_vm_exec_context(struct sigcontext __user *uctx) > +{ > + struct sigcontext ctx = {}; > + sigset_t set = {}; > + > + > + if (copy_from_user(&ctx, uctx, CONTEXT_COPY_SIZE)) > + return -EFAULT; > + /* A floating point state is managed from user-space. */ > + if (ctx.fpstate != 0) > + return -EINVAL; > + if (!user_access_begin(uctx, sizeof(*uctx))) > + return -EFAULT; > + unsafe_put_sigcontext(uctx, NULL, current_pt_regs(), (&set), Efault); > + user_access_end(); But here you save the sigcontext without FPU state. > + > + if (__restore_sigcontext(current_pt_regs(), &ctx, 0)) > + goto badframe; And here you restore sigcontext, *with* FPU state. At which point your FPU state is irrecoverably lost. Also, I'm not at all convinced this can ever do the right thing when the tasks don't agree on what the FPU state is. I suppose in the best case the save will EFAULT. > + > + return 0; > +Efault: > + user_access_end(); > +badframe: > + signal_fault(current_pt_regs(), uctx, "swap_vm_exec_context"); > + return -EFAULT; > +} _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um
next prev parent reply other threads:[~2021-07-02 8:51 UTC|newest] Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-04-14 5:52 [PATCH 0/4 POC] Allow executing code and syscalls in another address space Andrei Vagin 2021-04-14 5:52 ` Andrei Vagin 2021-04-14 5:52 ` [PATCH 1/4] signal: add a helper to restore a process state from sigcontex Andrei Vagin 2021-04-14 5:52 ` Andrei Vagin 2021-04-14 5:52 ` [PATCH 2/4] arch/x86: implement the process_vm_exec syscall Andrei Vagin 2021-04-14 5:52 ` Andrei Vagin 2021-04-14 17:09 ` Oleg Nesterov 2021-04-14 17:09 ` Oleg Nesterov 2021-04-23 6:59 ` Andrei Vagin 2021-04-23 6:59 ` Andrei Vagin 2021-06-28 16:13 ` Jann Horn 2021-06-28 16:13 ` Jann Horn 2021-06-28 16:30 ` Andy Lutomirski 2021-06-28 17:14 ` Jann Horn 2021-06-28 17:14 ` Jann Horn 2021-06-28 18:18 ` Eric W. Biederman 2021-06-28 18:18 ` Eric W. Biederman 2021-06-29 1:01 ` Andrei Vagin 2021-06-29 1:01 ` Andrei Vagin 2021-07-02 6:22 ` Andrei Vagin 2021-07-02 6:22 ` Andrei Vagin 2021-07-02 11:51 ` Jann Horn 2021-07-02 11:51 ` Jann Horn 2021-07-02 11:51 ` Jann Horn 2021-07-02 20:40 ` Andy Lutomirski 2021-07-02 20:40 ` Andy Lutomirski 2021-07-02 8:51 ` Peter Zijlstra [this message] 2021-07-02 8:51 ` Peter Zijlstra 2021-07-02 22:21 ` Andrei Vagin 2021-07-02 22:21 ` Andrei Vagin 2021-07-02 20:56 ` Jann Horn 2021-07-02 20:56 ` Jann Horn 2021-07-02 22:48 ` Andrei Vagin 2021-07-02 22:48 ` Andrei Vagin 2021-04-14 5:52 ` [PATCH 3/4] arch/x86: allow to execute syscalls via process_vm_exec Andrei Vagin 2021-04-14 5:52 ` Andrei Vagin 2021-04-14 5:52 ` [PATCH 4/4] selftests: add tests for process_vm_exec Andrei Vagin 2021-04-14 5:52 ` Andrei Vagin 2021-04-14 6:46 ` [PATCH 0/4 POC] Allow executing code and syscalls in another address space Jann Horn 2021-04-14 6:46 ` Jann Horn 2021-04-14 22:10 ` Andrei Vagin 2021-04-14 22:10 ` Andrei Vagin 2021-07-02 6:57 ` Andrei Vagin 2021-07-02 6:57 ` Andrei Vagin 2021-07-02 15:12 ` Jann Horn 2021-07-02 15:12 ` Jann Horn 2021-07-02 15:12 ` Jann Horn 2021-07-18 0:38 ` Andrei Vagin 2021-07-18 0:38 ` Andrei Vagin 2021-04-14 7:22 ` Anton Ivanov 2021-04-14 7:22 ` Anton Ivanov 2021-04-14 7:34 ` Johannes Berg 2021-04-14 7:34 ` Johannes Berg 2021-04-14 9:24 ` Benjamin Berg 2021-04-14 9:24 ` Benjamin Berg 2021-04-14 10:27 ` Florian Weimer 2021-04-14 10:27 ` Florian Weimer 2021-04-14 11:24 ` Jann Horn 2021-04-14 11:24 ` Jann Horn 2021-04-14 12:20 ` Florian Weimer 2021-04-14 12:20 ` Florian Weimer 2021-04-14 13:58 ` Jann Horn 2021-04-14 13:58 ` Jann Horn 2021-04-16 19:29 ` Kirill Smelkov 2021-04-16 19:29 ` Kirill Smelkov 2021-04-17 16:28 ` sbaugh 2021-04-17 16:28 ` sbaugh 2021-07-02 22:44 ` Andy Lutomirski 2021-07-02 22:44 ` Andy Lutomirski 2021-07-18 1:34 ` Andrei Vagin 2021-07-18 1:34 ` Andrei Vagin
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=YN7TgV9RDJTRaY8R@hirez.programming.kicks-ass.net \ --to=peterz@infradead.org \ --cc=0x7f454c46@gmail.com \ --cc=akpm@linux-foundation.org \ --cc=anton.ivanov@cambridgegreys.com \ --cc=avagin@gmail.com \ --cc=avagin@google.com \ --cc=christian.brauner@ubuntu.com \ --cc=criu@openvz.org \ --cc=jdike@addtoit.com \ --cc=linux-api@vger.kernel.org \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-um@lists.infradead.org \ --cc=luto@kernel.org \ --cc=mingo@redhat.com \ --cc=mtk.manpages@gmail.com \ --cc=oleg@redhat.com \ --cc=richard@nod.at \ --cc=rppt@linux.ibm.com \ --cc=tglx@linutronix.de \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.