From: KP Singh <kpsingh@chromium.org> To: linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-security-module@vger.kernel.org Cc: "Alexei Starovoitov" <ast@kernel.org>, "Daniel Borkmann" <daniel@iogearbox.net>, "James Morris" <jmorris@namei.org>, "Kees Cook" <keescook@chromium.org>, "Thomas Garnier" <thgarnie@chromium.org>, "Michael Halcrow" <mhalcrow@google.com>, "Paul Turner" <pjt@google.com>, "Brendan Gregg" <brendan.d.gregg@gmail.com>, "Jann Horn" <jannh@google.com>, "Matthew Garrett" <mjg59@google.com>, "Christian Brauner" <christian@brauner.io>, "Mickaël Salaün" <mic@digikod.net>, "Florent Revest" <revest@chromium.org>, "Martin KaFai Lau" <kafai@fb.com>, "Song Liu" <songliubraving@fb.com>, "Yonghong Song" <yhs@fb.com>, "Serge E. Hallyn" <serge@hallyn.com>, "Mauro Carvalho Chehab" <mchehab+samsung@kernel.org>, "David S. Miller" <davem@davemloft.net>, "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>, "Nicolas Ferre" <nicolas.ferre@microchip.com>, "Stanislav Fomichev" <sdf@google.com>, "Quentin Monnet" <quentin.monnet@netronome.com>, "Andrey Ignatov" <rdna@fb.com>, "Joe Stringer" <joe@wand.net.nz> Subject: [RFC v1 11/14] krsi: Pin argument pages in bprm_check_security hook Date: Tue, 10 Sep 2019 13:55:24 +0200 [thread overview] Message-ID: <20190910115527.5235-12-kpsingh@chromium.org> (raw) In-Reply-To: <20190910115527.5235-1-kpsingh@chromium.org> From: KP Singh <kpsingh@google.com> Pin the memory allocated to the the argv + envv for the new process and passes it in the context to the eBPF programs attached to the hook. The get_user_pages_remote cannot be called from an eBPF helper because the helpers run in atomic context and the get_user_pages_remote function can sleep. The following heuristics can be added as an optimization: - Don't pin the pages if no eBPF programs are attached. - Don't pin the pages if none of the eBPF programs depend on the information. This would require introspection of the byte-code and checking if certain helpers are called. Signed-off-by: KP Singh <kpsingh@google.com> --- security/krsi/include/krsi_init.h | 3 ++ security/krsi/krsi.c | 56 +++++++++++++++++++++++++++++++ 2 files changed, 59 insertions(+) diff --git a/security/krsi/include/krsi_init.h b/security/krsi/include/krsi_init.h index 4e17ecacd4ed..6152847c3b08 100644 --- a/security/krsi/include/krsi_init.h +++ b/security/krsi/include/krsi_init.h @@ -16,6 +16,9 @@ extern int krsi_fs_initialized; struct krsi_bprm_ctx { struct linux_binprm *bprm; + char *arg_pages; + unsigned long num_arg_pages; + unsigned long max_arg_offset; }; /* diff --git a/security/krsi/krsi.c b/security/krsi/krsi.c index d3a4a361c192..00a7150c1b22 100644 --- a/security/krsi/krsi.c +++ b/security/krsi/krsi.c @@ -4,6 +4,8 @@ #include <linux/filter.h> #include <linux/bpf.h> #include <linux/binfmts.h> +#include <linux/highmem.h> +#include <linux/mm.h> #include "krsi_init.h" @@ -17,6 +19,53 @@ struct krsi_hook krsi_hooks_list[] = { #undef KRSI_HOOK_INIT }; +static int pin_arg_pages(struct krsi_bprm_ctx *ctx) +{ + int ret = 0; + char *kaddr; + struct page *page; + unsigned long i, pos, num_arg_pages; + struct linux_binprm *bprm = ctx->bprm; + char *buf; + + /* + * The bprm->vma_pages does not have the correct count + * for execution that is done by a kernel thread using the UMH. + * vm_pages is updated in acct_arg_size and bails + * out if current->mm is NULL (which is the case for a kernel thread). + * It's safer to use vma_pages(struct linux_binprm*) to get the + * actual number + */ + num_arg_pages = vma_pages(bprm->vma); + if (!num_arg_pages) + return -ENOMEM; + + buf = kmalloc_array(num_arg_pages, PAGE_SIZE, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + for (i = 0; i < num_arg_pages; i++) { + pos = ALIGN_DOWN(bprm->p, PAGE_SIZE) + i * PAGE_SIZE; + ret = get_user_pages_remote(current, bprm->mm, pos, 1, + FOLL_FORCE, &page, NULL, NULL); + if (ret <= 0) { + kfree(buf); + return -ENOMEM; + } + + kaddr = kmap(page); + memcpy(buf + i * PAGE_SIZE, kaddr, PAGE_SIZE); + kunmap(page); + put_page(page); + } + + ctx->arg_pages = buf; + ctx->num_arg_pages = num_arg_pages; + ctx->max_arg_offset = num_arg_pages * PAGE_SIZE; + + return 0; +} + static int krsi_process_execution(struct linux_binprm *bprm) { int ret; @@ -26,7 +75,14 @@ static int krsi_process_execution(struct linux_binprm *bprm) .bprm = bprm, }; + ret = pin_arg_pages(&ctx.bprm_ctx); + if (ret < 0) + goto out_arg_pages; + ret = krsi_run_progs(PROCESS_EXECUTION, &ctx); + kfree(ctx.bprm_ctx.arg_pages); + +out_arg_pages: return ret; } -- 2.20.1
next prev parent reply other threads:[~2019-09-10 11:57 UTC|newest] Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-09-10 11:55 [RFC v1 00/14] Kernel Runtime Security Instrumentation KP Singh 2019-09-10 11:55 ` [RFC v1 01/14] krsi: Add a skeleton and config options for the KRSI LSM KP Singh 2019-09-10 11:55 ` [RFC v1 02/14] krsi: Introduce types for KRSI eBPF KP Singh 2019-09-10 11:55 ` [RFC v1 03/14] bpf: krsi: sync BPF UAPI header with tools KP Singh 2019-09-10 11:55 ` [RFC v1 04/14] krsi: Add support in libbpf for BPF_PROG_TYPE_KRSI KP Singh 2019-09-14 16:09 ` Yonghong Song 2019-09-10 11:55 ` [RFC v1 05/14] krsi: Initialize KRSI hooks and create files in securityfs KP Singh 2019-09-14 16:26 ` Yonghong Song 2019-09-10 11:55 ` [RFC v1 06/14] krsi: Implement eBPF operations, attachment and execution KP Singh 2019-09-14 16:56 ` Yonghong Song 2019-09-15 0:37 ` Yonghong Song 2019-09-10 11:55 ` [RFC v1 07/14] krsi: Check for premissions on eBPF attachment KP Singh 2019-09-10 11:55 ` [RFC v1 08/14] krsi: Show attached program names in hook read handler KP Singh 2019-09-10 11:55 ` [RFC v1 09/14] krsi: Add a helper function for bpf_perf_event_output KP Singh 2019-09-14 18:23 ` Yonghong Song 2019-09-10 11:55 ` [RFC v1 10/14] krsi: Handle attachment of the same program KP Singh 2019-09-10 11:55 ` KP Singh [this message] 2019-09-10 11:55 ` [RFC v1 12/14] krsi: Add an eBPF helper function to get the value of an env variable KP Singh 2019-09-15 0:16 ` Yonghong Song 2019-09-16 13:00 ` KP Singh 2019-09-17 16:58 ` Yonghong Song 2019-09-17 19:36 ` KP Singh 2019-09-10 11:55 ` [RFC v1 13/14] krsi: Provide an example to read and log environment variables KP Singh 2019-09-15 0:24 ` Yonghong Song 2019-09-10 11:55 ` [RFC v1 14/14] krsi: Pin arg pages only when needed KP Singh 2019-09-15 0:33 ` Yonghong Song 2019-09-15 1:40 ` KP Singh 2019-09-15 19:45 ` Yonghong Song
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