2022-09-29 08:24:20

by xu.panda668

Subject: [PATCH linux-next] arm64/idreg: use strscpy() is more robust and safer

From: Xu Panda <[email protected]>

The implementation of strscpy() is more robust and safer.
That's now the recommended way to copy NUL terminated strings.

Reported-by: Zeal Robot <[email protected]>
Signed-off-by: Xu Panda <[email protected]>
Signed-off-by: Xu Panda <[email protected]>
---
arch/arm64/kernel/idreg-override.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index 95133765ed29..61bbec7ef62e 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -246,7 +246,7 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
return;

len = min(len, ARRAY_SIZE(buf) - 1);
- strncpy(buf, cmdline, len);
+ strscpy(buf, cmdline, len);
buf[len] = 0;

if (strcmp(buf, "--") == 0)
--
2.15.2

2022-10-04 11:51:59

by Will Deacon

Subject: Re: [PATCH linux-next] arm64/idreg: use strscpy() is more robust and safer

On Thu, Sep 29, 2022 at 07:29:06AM +0000, [email protected] wrote:
> From: Xu Panda <[email protected]>
>
> The implementation of strscpy() is more robust and safer.
> That's now the recommended way to copy NUL terminated strings.
>
> Reported-by: Zeal Robot <[email protected]>
> Signed-off-by: Xu Panda <[email protected]>
> Signed-off-by: Xu Panda <[email protected]>
> ---
> arch/arm64/kernel/idreg-override.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
> index 95133765ed29..61bbec7ef62e 100644
> --- a/arch/arm64/kernel/idreg-override.c
> +++ b/arch/arm64/kernel/idreg-override.c
> @@ -246,7 +246,7 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
> return;
>
> len = min(len, ARRAY_SIZE(buf) - 1);
> - strncpy(buf, cmdline, len);
> + strscpy(buf, cmdline, len);
> buf[len] = 0;

Aren't we terminating the buffer explicitly here anyway?

Will

2022-10-05 14:04:59

by David Laight

Subject: RE: [PATCH linux-next] arm64/idreg: use strscpy() is more robust and safer

From: Will Deacon
> Sent: 04 October 2022 12:48
>
> On Thu, Sep 29, 2022 at 07:29:06AM +0000, [email protected] wrote:
> > From: Xu Panda <[email protected]>
> >
> > The implementation of strscpy() is more robust and safer.
> > That's now the recommended way to copy NUL terminated strings.

In this case the input string isn't NUL terminated....

> >
> > Reported-by: Zeal Robot <[email protected]>
> > Signed-off-by: Xu Panda <[email protected]>
> > Signed-off-by: Xu Panda <[email protected]>
> > ---
> > arch/arm64/kernel/idreg-override.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
> > index 95133765ed29..61bbec7ef62e 100644
> > --- a/arch/arm64/kernel/idreg-override.c
> > +++ b/arch/arm64/kernel/idreg-override.c
> > @@ -246,7 +246,7 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
> > return;
> >
> > len = min(len, ARRAY_SIZE(buf) - 1);
> > - strncpy(buf, cmdline, len);
> > + strscpy(buf, cmdline, len);
> > buf[len] = 0;
>
> Aren't we terminating the buffer explicitly here anyway?

I doubt the code was tested.
It is always wrong regardless of the initial value of 'len'.

I think using strscpy() will delete the last character
and always add two '\0'.

On the face of it, that could probably be a memcpy().

But with the checks you don't need any of the length
checks that memcpy() might be gaining.

OTOH, if the code used parameqn() a few lines lower the
entire copy could be removed.

David

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