From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Safonov Subject: [PATCH 32/32] x86/vdso: Restrict splitting VVAR VMA Date: Wed, 6 Feb 2019 00:11:06 +0000 Message-ID: <20190206001107.16488-33-dima@arista.com> References: <20190206001107.16488-1-dima@arista.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20190206001107.16488-1-dima@arista.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: Dmitry Safonov , Adrian Reber , Andrei Vagin , Andrei Vagin , Andy Lutomirski , Andy Tucker , Arnd Bergmann , Christian Brauner , Cyrill Gorcunov , Dmitry Safonov <0x7f454c46@gmail.com>, "Eric W. Biederman" , "H. Peter Anvin" , Ingo Molnar , Jeff Dike , Oleg Nesterov , Pavel Emelyanov , Shuah Khan , Thomas Gleixner , containers@lists.linux-foundation.org, criu@openvz.org, linux-api@vger.kernel.org, x86@kernel.org List-Id: linux-api@vger.kernel.org Although, time namespace can work with VVAR VMA split, it seems worth to forbid splitting VVAR resulting in stricter ABI and reducing amount of corner-cases to consider while working further on VDSO. I don't think there is any use-case for partial mremap() of vvar, but it there is - this patch can be easily dropped. Signed-off-by: Dmitry Safonov --- arch/x86/entry/vdso/vma.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c index 52c1e4c24455..dc1fca4d935a 100644 --- a/arch/x86/entry/vdso/vma.c +++ b/arch/x86/entry/vdso/vma.c @@ -87,6 +87,18 @@ static int vdso_mremap(const struct vm_special_mapping *sm, return 0; } +static int vvar_mremap(const struct vm_special_mapping *sm, + struct vm_area_struct *new_vma) +{ + unsigned long new_size = new_vma->vm_end - new_vma->vm_start; + const struct vdso_image *image = current->mm->context.vdso_image; + + if (new_size != -image->sym_vvar_start) + return -EINVAL; + + return 0; +} + static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, struct vm_area_struct *vma, struct vm_fault *vmf) { @@ -149,6 +161,7 @@ static const struct vm_special_mapping vdso_mapping = { static const struct vm_special_mapping vvar_mapping = { .name = "[vvar]", .fault = vvar_fault, + .mremap = vvar_mremap, }; #ifdef CONFIG_TIME_NS -- 2.20.1