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Date: Tue, 23 Jul 2019 14:29:10 -0700
From: Kees Cook <keescook@...omium.org>
To: Joe Perches <joe@...ches.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-kernel@...r.kernel.org, Jonathan Corbet <corbet@....net>,
Stephen Kitt <steve@....org>, Nitin Gote <nitin.r.gote@...el.com>,
jannh@...gle.com, kernel-hardening@...ts.openwall.com,
Rasmus Villemoes <rasmus.villemoes@...vas.dk>
Subject: Re: [PATCH 1/2] string: Add stracpy and stracpy_pad mechanisms
On Mon, Jul 22, 2019 at 09:42:51PM -0700, Joe Perches wrote:
> On Mon, 2019-07-22 at 21:35 -0700, Andrew Morton wrote:
> > On Mon, 22 Jul 2019 17:38:15 -0700 Joe Perches <joe@...ches.com> wrote:
> >
> > > Several uses of strlcpy and strscpy have had defects because the
> > > last argument of each function is misused or typoed.
> > >
> > > Add macro mechanisms to avoid this defect.
> > >
> > > stracpy (copy a string to a string array) must have a string
> > > array as the first argument (to) and uses sizeof(to) as the
> > > size.
> > >
> > > These mechanisms verify that the to argument is an array of
> > > char or other compatible types like u8 or unsigned char.
> > >
> > > A BUILD_BUG is emitted when the type of to is not compatible.
> > >
> >
> > It would be nice to include some conversions. To demonstrate the need,
> > to test the code, etc.
>
> How about all the kernel/ ?
> ---
> kernel/acct.c | 2 +-
> kernel/cgroup/cgroup-v1.c | 3 +--
> kernel/debug/gdbstub.c | 4 ++--
> kernel/debug/kdb/kdb_support.c | 2 +-
> kernel/events/core.c | 4 ++--
> kernel/module.c | 2 +-
> kernel/printk/printk.c | 2 +-
> kernel/time/clocksource.c | 2 +-
> 8 files changed, 10 insertions(+), 11 deletions(-)
I think that's a good start. I still think we could just give Linus a
Coccinelle script too, for the next merge window...
-Kees
>
> diff --git a/kernel/acct.c b/kernel/acct.c
> index 81f9831a7859..5ad29248b654 100644
> --- a/kernel/acct.c
> +++ b/kernel/acct.c
> @@ -425,7 +425,7 @@ static void fill_ac(acct_t *ac)
> memset(ac, 0, sizeof(acct_t));
>
> ac->ac_version = ACCT_VERSION | ACCT_BYTEORDER;
> - strlcpy(ac->ac_comm, current->comm, sizeof(ac->ac_comm));
> + stracpy(ac->ac_comm, current->comm);
>
> /* calculate run_time in nsec*/
> run_time = ktime_get_ns();
> diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
> index 88006be40ea3..dd4f041e4179 100644
> --- a/kernel/cgroup/cgroup-v1.c
> +++ b/kernel/cgroup/cgroup-v1.c
> @@ -571,8 +571,7 @@ static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
> if (!cgrp)
> return -ENODEV;
> spin_lock(&release_agent_path_lock);
> - strlcpy(cgrp->root->release_agent_path, strstrip(buf),
> - sizeof(cgrp->root->release_agent_path));
> + stracpy(cgrp->root->release_agent_path, strstrip(buf));
> spin_unlock(&release_agent_path_lock);
> cgroup_kn_unlock(of->kn);
> return nbytes;
> diff --git a/kernel/debug/gdbstub.c b/kernel/debug/gdbstub.c
> index 4b280fc7dd67..a263f27f51ad 100644
> --- a/kernel/debug/gdbstub.c
> +++ b/kernel/debug/gdbstub.c
> @@ -1095,10 +1095,10 @@ int gdbstub_state(struct kgdb_state *ks, char *cmd)
> return error;
> case 's':
> case 'c':
> - strscpy(remcom_in_buffer, cmd, sizeof(remcom_in_buffer));
> + stracpy(remcom_in_buffer, cmd);
> return 0;
> case '$':
> - strscpy(remcom_in_buffer, cmd, sizeof(remcom_in_buffer));
> + stracpy(remcom_in_buffer, cmd);
> gdbstub_use_prev_in_buf = strlen(remcom_in_buffer);
> gdbstub_prev_in_buf_pos = 0;
> return 0;
> diff --git a/kernel/debug/kdb/kdb_support.c b/kernel/debug/kdb/kdb_support.c
> index b8e6306e7e13..b49b6c3976c7 100644
> --- a/kernel/debug/kdb/kdb_support.c
> +++ b/kernel/debug/kdb/kdb_support.c
> @@ -192,7 +192,7 @@ int kallsyms_symbol_complete(char *prefix_name, int max_len)
>
> while ((name = kdb_walk_kallsyms(&pos))) {
> if (strncmp(name, prefix_name, prefix_len) == 0) {
> - strscpy(ks_namebuf, name, sizeof(ks_namebuf));
> + stracpy(ks_namebuf, name);
> /* Work out the longest name that matches the prefix */
> if (++number == 1) {
> prev_len = min_t(int, max_len-1,
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 026a14541a38..25bd8c777270 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -7049,7 +7049,7 @@ static void perf_event_comm_event(struct perf_comm_event *comm_event)
> unsigned int size;
>
> memset(comm, 0, sizeof(comm));
> - strlcpy(comm, comm_event->task->comm, sizeof(comm));
> + stracpy(comm, comm_event->task->comm);
> size = ALIGN(strlen(comm)+1, sizeof(u64));
>
> comm_event->comm = comm;
> @@ -7394,7 +7394,7 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
> }
>
> cpy_name:
> - strlcpy(tmp, name, sizeof(tmp));
> + stracpy(tmp, name);
> name = tmp;
> got_name:
> /*
> diff --git a/kernel/module.c b/kernel/module.c
> index 5933395af9a0..39384b0c90b8 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -1021,7 +1021,7 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
> async_synchronize_full();
>
> /* Store the name of the last unloaded module for diagnostic purposes */
> - strlcpy(last_unloaded_module, mod->name, sizeof(last_unloaded_module));
> + stracpy(last_unloaded_module, mod->name);
>
> free_module(mod);
> return 0;
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 424abf802f02..029633052be4 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -2127,7 +2127,7 @@ static int __add_preferred_console(char *name, int idx, char *options,
> return -E2BIG;
> if (!brl_options)
> preferred_console = i;
> - strlcpy(c->name, name, sizeof(c->name));
> + stracpy(c->name, name);
> c->options = options;
> braille_set_options(c, brl_options);
>
> diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
> index fff5f64981c6..f0c833d89ace 100644
> --- a/kernel/time/clocksource.c
> +++ b/kernel/time/clocksource.c
> @@ -1203,7 +1203,7 @@ static int __init boot_override_clocksource(char* str)
> {
> mutex_lock(&clocksource_mutex);
> if (str)
> - strlcpy(override_name, str, sizeof(override_name));
> + stracpy(override_name, str);
> mutex_unlock(&clocksource_mutex);
> return 1;
> }
>
>
--
Kees Cook
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