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Message-ID: <ZPhsSzHG6YMViOSk@gmail.com>
Date: Wed, 6 Sep 2023 14:10:51 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Justin Stitt <justinstitt@...gle.com>
Cc: Steve Wahl <steve.wahl@....com>, Mike Travis <mike.travis@....com>,
Dimitri Sivanich <dimitri.sivanich@....com>,
Russ Anderson <russ.anderson@....com>,
Darren Hart <dvhart@...radead.org>,
Andy Shevchenko <andy@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>,
platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
Hans de Goede <hdegoede@...hat.com>,
linux-hardening@...r.kernel.org
Subject: Re: [PATCH v3] x86/platform/uv: refactor deprecated strcpy and
strncpy
* Justin Stitt <justinstitt@...gle.com> wrote:
> Both `strncpy` and `strcpy` are deprecated for use on NUL-terminated
> destination strings [1].
>
> We can see that `arg` and `uv_nmi_action` are expected to be
> NUL-terminated strings due to their use within `strcmp()` and format
> strings respectively.
>
> With this in mind, a suitable replacement is `strscpy` [2] due to the
> fact that it guarantees NUL-termination on its destination buffer
> argument which is _not_ the case for `strncpy` or `strcpy`!
>
> In this case, we can drop both the forced NUL-termination and the `... -1` from:
> | strncpy(arg, val, ACTION_LEN - 1);
> as `strscpy` implicitly has this behavior.
>
> Link: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings[1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> arch/x86/platform/uv/uv_nmi.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
Note that this commit is already upstream:
1e6f01f72855 ("x86/platform/uv: Refactor code using deprecated strcpy()/strncpy() interfaces to use strscpy()")
Below is the delta your v3 patch has compared to what is upstream - is it
really necessary to open code it, instead of using strnchrnul() as your
original patch did? Am I missing anything here?
Thanks,
Ingo
--- a/arch/x86/platform/uv/uv_nmi.c
+++ b/arch/x86/platform/uv/uv_nmi.c
@@ -202,10 +202,13 @@ static int param_set_action(const char *val, const struct kernel_param *kp)
{
int i;
int n = ARRAY_SIZE(valid_acts);
- char arg[ACTION_LEN];
+ char arg[ACTION_LEN], *p;
/* (remove possible '\n') */
- strscpy(arg, val, strnchrnul(val, sizeof(arg)-1, '\n') - val + 1);
+ strscpy(arg, val, sizeof(arg));
+ p = strchr(arg, '\n');
+ if (p)
+ *p = '\0';
for (i = 0; i < n; i++)
if (!strcmp(arg, valid_acts[i].action))
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