From: Steven Rostedt <rostedt@goodmis.org>
To: Romain Perier <romain.perier@gmail.com>
Cc: Kees Cook <keescook@chromium.org>,
kernel-hardening@lists.openwall.com,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 16/20] tracing/probe: Manual replacement of the deprecated strlcpy() with return values
Date: Mon, 22 Feb 2021 12:49:36 -0500 [thread overview]
Message-ID: <20210222124936.03103585@gandalf.local.home> (raw)
In-Reply-To: <20210222151231.22572-17-romain.perier@gmail.com>
On Mon, 22 Feb 2021 16:12:27 +0100
Romain Perier <romain.perier@gmail.com> wrote:
> The strlcpy() reads the entire source buffer first, it is dangerous if
> the source buffer lenght is unbounded or possibility non NULL-terminated.
> It can lead to linear read overflows, crashes, etc...
>
> As recommended in the deprecated interfaces [1], it should be replaced
> by strscpy.
>
> This commit replaces all calls to strlcpy that handle the return values
> by the corresponding strscpy calls with new handling of the return
> values (as it is quite different between the two functions).
>
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
>
> Signed-off-by: Romain Perier <romain.perier@gmail.com>
> ---
> kernel/trace/trace_uprobe.c | 11 +++++------
> 1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index 3cf7128e1ad3..f9583afdb735 100644
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -154,12 +154,11 @@ fetch_store_string(unsigned long addr, void *dest, void *base)
> u8 *dst = get_loc_data(dest, base);
> void __user *src = (void __force __user *) addr;
>
> - if (unlikely(!maxlen))
> - return -ENOMEM;
Don't remove the above. You just broke the else side.
> -
> - if (addr == FETCH_TOKEN_COMM)
> - ret = strlcpy(dst, current->comm, maxlen);
> - else
> + if (addr == FETCH_TOKEN_COMM) {
> + ret = strscpy(dst, current->comm, maxlen);
> + if (ret == -E2BIG)
> + return -ENOMEM;
I'm not sure the above is what we want. current->comm is always nul
terminated, and not only that, it will never be bigger than TASK_COMM_LEN.
If the "dst" location is smaller than comm (maxlen < TASK_COMM_LEN), it is
still OK to copy a partial string. It should not return -ENOMEM which looks
to be what happens with this patch.
In other words, it looks like this patch breaks the current code in more
ways than one.
-- Steve
> + } else
> ret = strncpy_from_user(dst, src, maxlen);
> if (ret >= 0) {
> if (ret == maxlen)
next prev parent reply other threads:[~2021-02-22 17:51 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-22 15:12 [PATCH 00/20] Manual replacement of all strlcpy in favor of strscpy Romain Perier
2021-02-22 15:12 ` [PATCH 01/20] cgroup: Manual replacement of the deprecated strlcpy() with return values Romain Perier
2021-02-23 16:13 ` Michal Koutný
2021-02-22 15:12 ` [PATCH 02/20] crypto: " Romain Perier
2021-03-04 4:37 ` Herbert Xu
2021-02-22 15:12 ` [PATCH 03/20] devlink: " Romain Perier
2021-02-23 0:56 ` Jakub Kicinski
2021-02-22 15:12 ` [PATCH 04/20] dma-buf: " Romain Perier
2021-02-22 15:12 ` [PATCH 05/20] kobject: " Romain Perier
2021-02-22 15:12 ` [PATCH 06/20] ima: " Romain Perier
2021-03-02 13:29 ` Mimi Zohar
2021-02-22 15:12 ` [PATCH 07/20] SUNRPC: " Romain Perier
2021-03-01 18:25 ` Chuck Lever
2021-02-22 15:12 ` [PATCH 08/20] kernfs: " Romain Perier
2021-02-22 15:12 ` [PATCH 09/20] m68k/atari: " Romain Perier
2021-02-22 15:12 ` [PATCH 10/20] module: " Romain Perier
2021-02-22 15:12 ` [PATCH 11/20] hwmon: " Romain Perier
2021-02-22 15:46 ` Guenter Roeck
2021-02-28 11:50 ` Joe Perches
2021-02-22 15:12 ` [PATCH 12/20] s390/hmcdrv: " Romain Perier
2021-02-22 15:12 ` [PATCH 13/20] scsi: zfcp: " Romain Perier
2021-02-22 16:04 ` Benjamin Block
2021-02-22 15:12 ` [PATCH 14/20] target: " Romain Perier
2021-02-22 16:00 ` Bodo Stroesser
2021-02-22 18:09 ` kernel test robot
2021-02-22 15:12 ` [PATCH 15/20] ALSA: usb-audio: " Romain Perier
2021-02-22 15:39 ` Takashi Iwai
2021-02-22 15:12 ` [PATCH 16/20] tracing/probe: " Romain Perier
2021-02-22 17:49 ` Steven Rostedt [this message]
2021-02-22 15:12 ` [PATCH 17/20] vt: " Romain Perier
2021-02-26 9:49 ` Jiri Slaby
2021-02-22 15:12 ` [PATCH 18/20] usb: gadget: f_midi: " Romain Perier
2021-02-22 15:12 ` [PATCH 19/20] usbip: usbip_host: " Romain Perier
2021-02-22 16:21 ` Shuah Khan
2021-02-28 9:03 ` Sergei Shtylyov
2021-02-22 15:12 ` [PATCH 20/20] s390/watchdog: " Romain Perier
2021-02-22 15:55 ` Guenter Roeck
2021-02-22 16:36 ` [PATCH 00/20] Manual replacement of all strlcpy in favor of strscpy Shuah Khan
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