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McKenney" , Boqun Feng , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Thomas Gleixner , Andy Lutomirski , Dave Watson , Paul Turner , Andrew Morton , Russell King , Ingo Molnar , "H . Peter Anvin" , Andi Kleen , Chris Lameter , Ben Maurer , Steven Rostedt , Josh Triplett , Linus Torvalds , Catalin Marinas , Will Deacon , Michael Kerrisk , Joel Fernandes Subject: Re: [RFC PATCH for 4.21 06/16] cpu_opv: Provide cpu_opv system call (v8) Message-ID: <20181016081029.GA30363@jagdpanzerIV> References: <20181010191936.7495-1-mathieu.desnoyers@efficios.com> <20181010191936.7495-7-mathieu.desnoyers@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181010191936.7495-7-mathieu.desnoyers@efficios.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mathieu, On (10/10/18 15:19), Mathieu Desnoyers wrote: [..] > +SYSCALL_DEFINE4(cpu_opv, struct cpu_op __user *, ucpuopv, int, cpuopcnt, > + int, cpu, int, flags) > +{ [..] > +again: > + ret = cpu_opv_pin_pages(cpuopv, cpuopcnt, &vaddr_ptrs); > + if (ret) > + goto end; > + ret = do_cpu_opv(cpuopv, cpuopcnt, &vaddr_ptrs, cpu); > + if (ret == -EAGAIN) > + retry = true; > +end: > + for (i = 0; i < vaddr_ptrs.nr_vaddr; i++) { > + struct vaddr *vaddr = &vaddr_ptrs.addr[i]; > + int j; > + > + vm_unmap_user_ram((void *)vaddr->mem, vaddr->nr_pages); A dumb question. Both vm_unmap_user_ram() and vm_map_user_ram() can BUG_ON(). So this is userspace -> syscall -> cpu_opv() -> vm_unmap_user_ram() -> BUG_ON() Any chance someone can exploit it? -ss