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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id f22sm1314244otf.50.2020.02.07.10.03.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 07 Feb 2020 10:03:18 -0800 (PST) Date: Fri, 7 Feb 2020 10:03:16 -0800 From: Kees Cook To: Masami Hiramatsu Cc: Steven Rostedt , Ingo Molnar , Frank Rowand , Randy Dunlap , Namhyung Kim , Tim Bird , Jiri Olsa , Arnaldo Carvalho de Melo , Tom Zanussi , Rob Herring , Andrew Morton , Thomas Gleixner , Greg Kroah-Hartman , Alexey Dobriyan , Jonathan Corbet , Linus Torvalds , linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 08/22] bootconfig: init: Allow admin to use bootconfig for init command line Message-ID: <202002070954.C18E7F58B@keescook> References: <157867220019.17873.13377985653744804396.stgit@devnote2> <157867229521.17873.654222294326542349.stgit@devnote2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <157867229521.17873.654222294326542349.stgit@devnote2> Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Sat, Jan 11, 2020 at 01:04:55AM +0900, Masami Hiramatsu wrote: > Since the current kernel command line is too short to describe > long and many options for init (e.g. systemd command line options), > this allows admin to use boot config for init command line. > > All init command line under "init." keywords will be passed to > init. > > For example, > > init.systemd { > unified_cgroup_hierarchy = 1 > debug_shell > default_timeout_start_sec = 60 > } > > Signed-off-by: Masami Hiramatsu > --- > init/main.c | 31 ++++++++++++++++++++++++++++--- > 1 file changed, 28 insertions(+), 3 deletions(-) > > diff --git a/init/main.c b/init/main.c > index c0017d9d16e7..dd7da62d99a5 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -139,6 +139,8 @@ char *saved_command_line; > static char *static_command_line; > /* Untouched extra command line */ > static char *extra_command_line; > +/* Extra init arguments */ > +static char *extra_init_args; > > static char *execute_command; > static char *ramdisk_execute_command; > @@ -372,6 +374,8 @@ static void __init setup_boot_config(void) > pr_info("Load boot config: %d bytes\n", size); > /* keys starting with "kernel." are passed via cmdline */ > extra_command_line = xbc_make_cmdline("kernel"); > + /* Also, "init." keys are init arguments */ > + extra_init_args = xbc_make_cmdline("init"); > } > } > #else > @@ -507,16 +511,18 @@ static inline void smp_prepare_cpus(unsigned int maxcpus) { } > */ > static void __init setup_command_line(char *command_line) > { > - size_t len, xlen = 0; > + size_t len, xlen = 0, ilen = 0; > > if (extra_command_line) > xlen = strlen(extra_command_line); > + if (extra_init_args) > + ilen = strlen(extra_init_args) + 4; /* for " -- " */ > > len = xlen + strlen(boot_command_line) + 1; > > - saved_command_line = memblock_alloc(len, SMP_CACHE_BYTES); > + saved_command_line = memblock_alloc(len + ilen, SMP_CACHE_BYTES); > if (!saved_command_line) > - panic("%s: Failed to allocate %zu bytes\n", __func__, len); > + panic("%s: Failed to allocate %zu bytes\n", __func__, len + ilen); > > static_command_line = memblock_alloc(len, SMP_CACHE_BYTES); > if (!static_command_line) > @@ -533,6 +539,22 @@ static void __init setup_command_line(char *command_line) > } > strcpy(saved_command_line + xlen, boot_command_line); > strcpy(static_command_line + xlen, command_line); > + > + if (ilen) { > + /* > + * Append supplemental init boot args to saved_command_line > + * so that user can check what command line options passed > + * to init. > + */ > + len = strlen(saved_command_line); > + if (!strstr(boot_command_line, " -- ")) { > + strcpy(saved_command_line + len, " -- "); > + len += 4; > + } else > + saved_command_line[len++] = ' '; > + > + strcpy(saved_command_line + len, extra_init_args); > + } This isn't safe because it will destroy any argument with " -- " in quotes and anything after it. For example, booting with: thing=on acpi_osi="! -- " other=setting will wreck acpi_osi's value and potentially overwrite "other=settings", etc. (Yes, this seems very unlikely, but you can't treat " -- " as special, the command line string must be correct parsed for double quotes, as parse_args() does.) > } > > /* > @@ -759,6 +781,9 @@ asmlinkage __visible void __init start_kernel(void) > if (!IS_ERR_OR_NULL(after_dashes)) > parse_args("Setting init args", after_dashes, NULL, 0, -1, -1, > NULL, set_init_arg); > + if (extra_init_args) > + parse_args("Setting extra init args", extra_init_args, > + NULL, 0, -1, -1, NULL, set_init_arg); Here is where you can append the extra_init_args, since parse_args() will have done the work to find after_dashes correctly. -Kees > > /* > * These use large bootmem allocations and must precede > -- Kees Cook