arch/x86/platform/uv/uv_nmi.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
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@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
Changes in v3:
- Use sizeof instead of strlen (thanks Andy and Dimitri)
- Drop unrelated changes regarding strnchrnul (thanks Hans)
- Link to v2: https://lore.kernel.org/r/20230824-strncpy-arch-x86-platform-uv-uv_nmi-v2-1-e16d9a3ec570@google.com
Changes in v2:
- use `sizeof` on destination string instead of `strlen` (thanks Andy, Kees and Dimitri)
- refactor code to remove potential new-line chars (thanks Yang Yang and Andy)
- Link to v1: https://lore.kernel.org/r/20230822-strncpy-arch-x86-platform-uv-uv_nmi-v1-1-931f2943de0d@google.com
---
Note: build-tested only
---
arch/x86/platform/uv/uv_nmi.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/x86/platform/uv/uv_nmi.c b/arch/x86/platform/uv/uv_nmi.c
index a60af0230e27..dd30fb2baf6c 100644
--- a/arch/x86/platform/uv/uv_nmi.c
+++ b/arch/x86/platform/uv/uv_nmi.c
@@ -205,8 +205,7 @@ static int param_set_action(const char *val, const struct kernel_param *kp)
char arg[ACTION_LEN], *p;
/* (remove possible '\n') */
- strncpy(arg, val, ACTION_LEN - 1);
- arg[ACTION_LEN - 1] = '\0';
+ strscpy(arg, val, sizeof(arg));
p = strchr(arg, '\n');
if (p)
*p = '\0';
@@ -216,7 +215,7 @@ static int param_set_action(const char *val, const struct kernel_param *kp)
break;
if (i < n) {
- strcpy(uv_nmi_action, arg);
+ strscpy(uv_nmi_action, arg, sizeof(uv_nmi_action));
pr_info("UV: New NMI action:%s\n", uv_nmi_action);
return 0;
}
@@ -959,7 +958,7 @@ static int uv_handle_nmi(unsigned int reason, struct pt_regs *regs)
/* Unexpected return, revert action to "dump" */
if (master)
- strncpy(uv_nmi_action, "dump", strlen(uv_nmi_action));
+ strscpy(uv_nmi_action, "dump", sizeof(uv_nmi_action));
}
/* Pause as all CPU's enter the NMI handler */
---
base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c
change-id: 20230822-strncpy-arch-x86-platform-uv-uv_nmi-474e5295c2c1
Best regards,
--
Justin Stitt <justinstitt@google.com>
* Justin Stitt <justinstitt@google.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@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.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))
Hi Ingo,
On 9/6/23 14:10, Ingo Molnar wrote:
>
> * Justin Stitt <justinstitt@google.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@vger.kernel.org
>> Signed-off-by: Justin Stitt <justinstitt@google.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?
The new version is a result of a review from my because IMHO:
strscpy(arg, val, strnchrnul(val, sizeof(arg)-1, '\n') - val + 1);
Is really unreadable / really hard to reason about if
this is actually correct and does not contain any
of by 1 bugs.
Note that the diff of v3 compared to the code before v2 landed is
actually smaller now and actually matches the subject of:
"refactor deprecated strcpy and strncpy"
Where as v2 actually touches more code / refactor things
which fall outside of a "one change per patch" approach.
The:
p = strchr(arg, '\n');
if (p)
*p = '\0';
was already there before v2 landed.
I also suggested to do a follow up patch to change things to:
strscpy(arg, val, sizeof(arg));
p = strchrnul(arg, '\n');
*p = '\0';
Which IMHO is much more readable then what has landed
now. But since v2 has already landed I guess the best
thing is just to stick with what we have upstream now...
Regards,
Hans
>
> 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))
>
* Hans de Goede <hdegoede@redhat.com> wrote:
> Hi Ingo,
>
> On 9/6/23 14:10, Ingo Molnar wrote:
> >
> > * Justin Stitt <justinstitt@google.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@vger.kernel.org
> >> Signed-off-by: Justin Stitt <justinstitt@google.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?
>
> The new version is a result of a review from my because IMHO:
>
> strscpy(arg, val, strnchrnul(val, sizeof(arg)-1, '\n') - val + 1);
>
> Is really unreadable / really hard to reason about if
> this is actually correct and does not contain any
> of by 1 bugs.
>
> Note that the diff of v3 compared to the code before v2 landed is
> actually smaller now and actually matches the subject of:
> "refactor deprecated strcpy and strncpy"
>
> Where as v2 actually touches more code / refactor things
> which fall outside of a "one change per patch" approach.
> The:
>
> p = strchr(arg, '\n');
> if (p)
> *p = '\0';
>
> was already there before v2 landed.
>
> I also suggested to do a follow up patch to change things to:
>
> strscpy(arg, val, sizeof(arg));
> p = strchrnul(arg, '\n');
> *p = '\0';
>
> Which IMHO is much more readable then what has landed
> now. But since v2 has already landed I guess the best
> thing is just to stick with what we have upstream now...
Well, how about we do a delta patch with all the changes
you suggested? I'm all for readability.
Thanks,
Ingo
Hi,
On 9/6/23 16:09, Ingo Molnar wrote:
>
> * Hans de Goede <hdegoede@redhat.com> wrote:
>
>> Hi Ingo,
>>
>> On 9/6/23 14:10, Ingo Molnar wrote:
>>>
>>> * Justin Stitt <justinstitt@google.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@vger.kernel.org
>>>> Signed-off-by: Justin Stitt <justinstitt@google.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?
>>
>> The new version is a result of a review from my because IMHO:
>>
>> strscpy(arg, val, strnchrnul(val, sizeof(arg)-1, '\n') - val + 1);
>>
>> Is really unreadable / really hard to reason about if
>> this is actually correct and does not contain any
>> of by 1 bugs.
>>
>> Note that the diff of v3 compared to the code before v2 landed is
>> actually smaller now and actually matches the subject of:
>> "refactor deprecated strcpy and strncpy"
>>
>> Where as v2 actually touches more code / refactor things
>> which fall outside of a "one change per patch" approach.
>> The:
>>
>> p = strchr(arg, '\n');
>> if (p)
>> *p = '\0';
>>
>> was already there before v2 landed.
>>
>> I also suggested to do a follow up patch to change things to:
>>
>> strscpy(arg, val, sizeof(arg));
>> p = strchrnul(arg, '\n');
>> *p = '\0';
>>
>> Which IMHO is much more readable then what has landed
>> now. But since v2 has already landed I guess the best
>> thing is just to stick with what we have upstream now...
>
> Well, how about we do a delta patch with all the changes
> you suggested? I'm all for readability.
So I started doing this and notices that all the string
manipulation + parsing done here is really just a DYI
implementation of sysfs_match_string().
So I have prepared a patch to switch to sysfs_match_string(),
which completely removes the need to make a copy of the val
string.
I'll submit the patch right after this email.
Regards,
Hans
* Hans de Goede <hdegoede@redhat.com> wrote: > >> Which IMHO is much more readable then what has landed now. But since > >> v2 has already landed I guess the best thing is just to stick with > >> what we have upstream now... > > > > Well, how about we do a delta patch with all the changes you suggested? > > I'm all for readability. > > So I started doing this and notices that all the string manipulation + > parsing done here is really just a DYI implementation of > sysfs_match_string(). > > So I have prepared a patch to switch to sysfs_match_string(), which > completely removes the need to make a copy of the val string. > > I'll submit the patch right after this email. Thank you - that looks a far more thorough cleanup indeed. Ingo
On Wed, Sep 06, 2023 at 04:09:01PM +0200, Ingo Molnar wrote:
>
> * Hans de Goede <hdegoede@redhat.com> wrote:
>
> > Hi Ingo,
> >
> > On 9/6/23 14:10, Ingo Molnar wrote:
> > >
> > > * Justin Stitt <justinstitt@google.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@vger.kernel.org
> > >> Signed-off-by: Justin Stitt <justinstitt@google.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?
> >
> > The new version is a result of a review from my because IMHO:
> >
> > strscpy(arg, val, strnchrnul(val, sizeof(arg)-1, '\n') - val + 1);
> >
> > Is really unreadable / really hard to reason about if
> > this is actually correct and does not contain any
> > of by 1 bugs.
> >
> > Note that the diff of v3 compared to the code before v2 landed is
> > actually smaller now and actually matches the subject of:
> > "refactor deprecated strcpy and strncpy"
> >
> > Where as v2 actually touches more code / refactor things
> > which fall outside of a "one change per patch" approach.
> > The:
> >
> > p = strchr(arg, '\n');
> > if (p)
> > *p = '\0';
> >
> > was already there before v2 landed.
> >
> > I also suggested to do a follow up patch to change things to:
> >
> > strscpy(arg, val, sizeof(arg));
> > p = strchrnul(arg, '\n');
> > *p = '\0';
> >
> > Which IMHO is much more readable then what has landed
> > now. But since v2 has already landed I guess the best
> > thing is just to stick with what we have upstream now...
>
> Well, how about we do a delta patch with all the changes
> you suggested? I'm all for readability.
For whatever it's worth, I vote in favor of adopting an increased
readability version.
I was on vacation when the patch came through, and by the time I
reviewed it it was already accepted. I still puzzled through the
-1/+1 stuff to be sure it functioned correctly; since it worked and
was already accepted, I let it go.
When Hans' comments on readability later came through, I was thinking
"Yes, he's exactly right! Why, when I worked so hard on verifying that
the code worked properly, did it not occur to me to suggest re-writing
this in a simpler fashion to make the intent clear?"
Thanks,
--> Steve Wahl
--
Steve Wahl, Hewlett Packard Enterprise
On Wed, Sep 6, 2023 at 3:16 PM Hans de Goede <hdegoede@redhat.com> wrote: > On 9/6/23 14:10, Ingo Molnar wrote: > strscpy(arg, val, strnchrnul(val, sizeof(arg)-1, '\n') - val + 1); If you want to make it short and more readable, you can use strscpy(arg, val, sizeof(arg)); strreplace(arg, '\n', '\0'); -- With Best Regards, Andy Shevchenko
Hi,
On 9/5/23 23:54, Justin Stitt 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@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>
> ---
> Changes in v3:
> - Use sizeof instead of strlen (thanks Andy and Dimitri)
> - Drop unrelated changes regarding strnchrnul (thanks Hans)
> - Link to v2: https://lore.kernel.org/r/20230824-strncpy-arch-x86-platform-uv-uv_nmi-v2-1-e16d9a3ec570@google.com
Thanks, patch looks good to me:
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Regards,
Hans
>
> Changes in v2:
> - use `sizeof` on destination string instead of `strlen` (thanks Andy, Kees and Dimitri)
> - refactor code to remove potential new-line chars (thanks Yang Yang and Andy)
> - Link to v1: https://lore.kernel.org/r/20230822-strncpy-arch-x86-platform-uv-uv_nmi-v1-1-931f2943de0d@google.com
> ---
> Note: build-tested only
> ---
> arch/x86/platform/uv/uv_nmi.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/platform/uv/uv_nmi.c b/arch/x86/platform/uv/uv_nmi.c
> index a60af0230e27..dd30fb2baf6c 100644
> --- a/arch/x86/platform/uv/uv_nmi.c
> +++ b/arch/x86/platform/uv/uv_nmi.c
> @@ -205,8 +205,7 @@ static int param_set_action(const char *val, const struct kernel_param *kp)
> char arg[ACTION_LEN], *p;
>
> /* (remove possible '\n') */
> - strncpy(arg, val, ACTION_LEN - 1);
> - arg[ACTION_LEN - 1] = '\0';
> + strscpy(arg, val, sizeof(arg));
> p = strchr(arg, '\n');
> if (p)
> *p = '\0';
> @@ -216,7 +215,7 @@ static int param_set_action(const char *val, const struct kernel_param *kp)
> break;
>
> if (i < n) {
> - strcpy(uv_nmi_action, arg);
> + strscpy(uv_nmi_action, arg, sizeof(uv_nmi_action));
> pr_info("UV: New NMI action:%s\n", uv_nmi_action);
> return 0;
> }
> @@ -959,7 +958,7 @@ static int uv_handle_nmi(unsigned int reason, struct pt_regs *regs)
>
> /* Unexpected return, revert action to "dump" */
> if (master)
> - strncpy(uv_nmi_action, "dump", strlen(uv_nmi_action));
> + strscpy(uv_nmi_action, "dump", sizeof(uv_nmi_action));
> }
>
> /* Pause as all CPU's enter the NMI handler */
>
> ---
> base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c
> change-id: 20230822-strncpy-arch-x86-platform-uv-uv_nmi-474e5295c2c1
>
> Best regards,
> --
> Justin Stitt <justinstitt@google.com>
>
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