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McKenney" , Boqun Feng , linux-kernel , linux-api , Thomas Gleixner , Andy Lutomirski , Dave Watson , Paul Turner , Andrew Morton , Russell King , Ingo Molnar , "H. Peter Anvin" , Andi Kleen , Chris Lameter , Ben Maurer , 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: <20181017014651.GB1068@jagdpanzerIV> References: <20181010191936.7495-1-mathieu.desnoyers@efficios.com> <20181010191936.7495-7-mathieu.desnoyers@efficios.com> <20181016081029.GA30363@jagdpanzerIV> <1984292897.263.1539717457933.JavaMail.zimbra@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1984292897.263.1539717457933.JavaMail.zimbra@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 (10/16/18 15:17), Mathieu Desnoyers wrote: > > Therefore, only an internal kernel bug between vm_map_user_ram() and > vm_unmap_user_ram() should trigger the BUG_ON(). No user input is passed > to vm_unmap_user_ram(). > > Now, let's look at vm_map_user_ram(). It calls alloc_vmap_area(), which returns > a vmap_area. Then if vmap_page_range failed, vm_unmap_user_ram is called on the > memory that has just been returned by vm_map_user_ram. Again, only an internal > bug between map/unmap can trigger the BUG_ON() in vm_unmap_user_ram. Thanks for spending time on this. Just wanted someone to have extra look at syscall->BUG_ON(). -ss