From: Jann Horn <jannh@google.com> 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>, Peter Zijlstra <peterz@infradead.org>, Richard Weinberger <richard@nod.at>, Thomas Gleixner <tglx@linutronix.de> Subject: Re: [PATCH 2/4] arch/x86: implement the process_vm_exec syscall Date: Mon, 28 Jun 2021 18:13:29 +0200 [thread overview] Message-ID: <CAG48ez3UrzPE8rkucTgCu8ggcTEjx_h3Gj2FES1qM-uv2KD8bQ@mail.gmail.com> (raw) In-Reply-To: <20210414055217.543246-3-avagin@gmail.com> On Wed, Apr 14, 2021 at 7:59 AM Andrei Vagin <avagin@gmail.com> wrote: > This change introduces the new system call: > process_vm_exec(pid_t pid, struct sigcontext *uctx, unsigned long flags, > siginfo_t * uinfo, sigset_t *sigmask, size_t sizemask) > > process_vm_exec allows to execute the current process in an address > space of another process. [...] I still think that this whole API is fundamentally the wrong approach because it tries to shoehorn multiple usecases with different requirements into a single API. But that aside: > +static void swap_mm(struct mm_struct *prev_mm, struct mm_struct *target_mm) > +{ > + struct task_struct *tsk = current; > + struct mm_struct *active_mm; > + > + task_lock(tsk); > + /* Hold off tlb flush IPIs while switching mm's */ > + local_irq_disable(); > + > + sync_mm_rss(prev_mm); > + > + vmacache_flush(tsk); > + > + active_mm = tsk->active_mm; > + if (active_mm != target_mm) { > + mmgrab(target_mm); > + tsk->active_mm = target_mm; > + } > + tsk->mm = target_mm; I'm pretty sure you're not currently allowed to overwrite the ->mm pointer of a userspace thread. For example, zap_threads() assumes that all threads running under a process have the same ->mm. (And if you're fiddling with ->mm stuff, you should probably CC linux-mm@.) As far as I understand, only kthreads are allowed to do this (as implemented in kthread_use_mm()). > + switch_mm_irqs_off(active_mm, target_mm, tsk); > + local_irq_enable(); > + task_unlock(tsk); > +#ifdef finish_arch_post_lock_switch > + finish_arch_post_lock_switch(); > +#endif > + > + if (active_mm != target_mm) > + mmdrop(active_mm); > +}
WARNING: multiple messages have this Message-ID (diff)
From: Jann Horn <jannh@google.com> 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>, Peter Zijlstra <peterz@infradead.org>, Richard Weinberger <richard@nod.at>, Thomas Gleixner <tglx@linutronix.de> Subject: Re: [PATCH 2/4] arch/x86: implement the process_vm_exec syscall Date: Mon, 28 Jun 2021 18:13:29 +0200 [thread overview] Message-ID: <CAG48ez3UrzPE8rkucTgCu8ggcTEjx_h3Gj2FES1qM-uv2KD8bQ@mail.gmail.com> (raw) In-Reply-To: <20210414055217.543246-3-avagin@gmail.com> On Wed, Apr 14, 2021 at 7:59 AM Andrei Vagin <avagin@gmail.com> wrote: > This change introduces the new system call: > process_vm_exec(pid_t pid, struct sigcontext *uctx, unsigned long flags, > siginfo_t * uinfo, sigset_t *sigmask, size_t sizemask) > > process_vm_exec allows to execute the current process in an address > space of another process. [...] I still think that this whole API is fundamentally the wrong approach because it tries to shoehorn multiple usecases with different requirements into a single API. But that aside: > +static void swap_mm(struct mm_struct *prev_mm, struct mm_struct *target_mm) > +{ > + struct task_struct *tsk = current; > + struct mm_struct *active_mm; > + > + task_lock(tsk); > + /* Hold off tlb flush IPIs while switching mm's */ > + local_irq_disable(); > + > + sync_mm_rss(prev_mm); > + > + vmacache_flush(tsk); > + > + active_mm = tsk->active_mm; > + if (active_mm != target_mm) { > + mmgrab(target_mm); > + tsk->active_mm = target_mm; > + } > + tsk->mm = target_mm; I'm pretty sure you're not currently allowed to overwrite the ->mm pointer of a userspace thread. For example, zap_threads() assumes that all threads running under a process have the same ->mm. (And if you're fiddling with ->mm stuff, you should probably CC linux-mm@.) As far as I understand, only kthreads are allowed to do this (as implemented in kthread_use_mm()). > + switch_mm_irqs_off(active_mm, target_mm, tsk); > + local_irq_enable(); > + task_unlock(tsk); > +#ifdef finish_arch_post_lock_switch > + finish_arch_post_lock_switch(); > +#endif > + > + if (active_mm != target_mm) > + mmdrop(active_mm); > +} _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um
next prev parent reply other threads:[~2021-06-28 16:14 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 [this message] 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 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
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