[RFC] string.h: Add stracpy/stracpy_pad (was: Re: [PATCH] checkpatch: Added warnings in favor of strscpy().)
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Message ID d1524130f91d7cfd61bc736623409693d2895f57.camel@perches.com
State New
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  • [RFC] string.h: Add stracpy/stracpy_pad (was: Re: [PATCH] checkpatch: Added warnings in favor of strscpy().)
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Commit Message

Joe Perches July 5, 2019, 12:15 a.m. UTC
On Thu, 2019-07-04 at 13:46 -0700, Joe Perches wrote:
> On Thu, 2019-07-04 at 11:24 +0530, Nitin Gote wrote:
> > Added warnings in checkpatch.pl script to :
> > 
> > 1. Deprecate strcpy() in favor of strscpy().
> > 2. Deprecate strlcpy() in favor of strscpy().
> > 3. Deprecate strncpy() in favor of strscpy() or strscpy_pad().
> > 
> > Updated strncpy() section in Documentation/process/deprecated.rst
> > to cover strscpy_pad() case.

[]

I sent a patch series for some strscpy/strlcpy misuses.

How about adding a macro helper to avoid the misuses like:
---
 include/linux/string.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

Comments

Kees Cook July 22, 2019, 5:33 p.m. UTC | #1
On Thu, Jul 04, 2019 at 05:15:57PM -0700, Joe Perches wrote:
> On Thu, 2019-07-04 at 13:46 -0700, Joe Perches wrote:
> > On Thu, 2019-07-04 at 11:24 +0530, Nitin Gote wrote:
> > > Added warnings in checkpatch.pl script to :
> > > 
> > > 1. Deprecate strcpy() in favor of strscpy().
> > > 2. Deprecate strlcpy() in favor of strscpy().
> > > 3. Deprecate strncpy() in favor of strscpy() or strscpy_pad().
> > > 
> > > Updated strncpy() section in Documentation/process/deprecated.rst
> > > to cover strscpy_pad() case.
> 
> []
> 
> I sent a patch series for some strscpy/strlcpy misuses.
> 
> How about adding a macro helper to avoid the misuses like:
> ---
>  include/linux/string.h | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/include/linux/string.h b/include/linux/string.h
> index 4deb11f7976b..ef01bd6f19df 100644
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -35,6 +35,22 @@ ssize_t strscpy(char *, const char *, size_t);
>  /* Wraps calls to strscpy()/memset(), no arch specific code required */
>  ssize_t strscpy_pad(char *dest, const char *src, size_t count);
>  
> +#define stracpy(to, from)					\
> +({								\
> +	size_t size = ARRAY_SIZE(to);				\
> +	BUILD_BUG_ON(!__same_type(typeof(*to), char));		\
> +								\
> +	strscpy(to, from, size);				\
> +})
> +
> +#define stracpy_pad(to, from)					\
> +({								\
> +	size_t size = ARRAY_SIZE(to);				\
> +	BUILD_BUG_ON(!__same_type(typeof(*to), char));		\
> +								\
> +	strscpy_pad(to, from, size);				\
> +})
> +
>  #ifndef __HAVE_ARCH_STRCAT
>  extern char * strcat(char *, const char *);
>  #endif

This seems like a reasonable addition, yes. I think Coccinelle might
actually be able to find all the existing strscpy(dst, src, sizeof(dst))
cases to jump-start this conversion.

Devil's advocate: this adds yet more string handling functions... will
this cause even more confusion?
Joe Perches July 22, 2019, 5:43 p.m. UTC | #2
On Mon, 2019-07-22 at 10:33 -0700, Kees Cook wrote:
> On Thu, Jul 04, 2019 at 05:15:57PM -0700, Joe Perches wrote:
> > On Thu, 2019-07-04 at 13:46 -0700, Joe Perches wrote:
> > > On Thu, 2019-07-04 at 11:24 +0530, Nitin Gote wrote:
> > > > Added warnings in checkpatch.pl script to :
> > > > 
> > > > 1. Deprecate strcpy() in favor of strscpy().
> > > > 2. Deprecate strlcpy() in favor of strscpy().
> > > > 3. Deprecate strncpy() in favor of strscpy() or strscpy_pad().
> > > > 
> > > > Updated strncpy() section in Documentation/process/deprecated.rst
> > > > to cover strscpy_pad() case.
> > 
> > []
> > 
> > I sent a patch series for some strscpy/strlcpy misuses.
> > 
> > How about adding a macro helper to avoid the misuses like:
> > ---
> >  include/linux/string.h | 16 ++++++++++++++++
> >  1 file changed, 16 insertions(+)
> > 
> > diff --git a/include/linux/string.h b/include/linux/string.h
> > index 4deb11f7976b..ef01bd6f19df 100644
> > --- a/include/linux/string.h
> > +++ b/include/linux/string.h
> > @@ -35,6 +35,22 @@ ssize_t strscpy(char *, const char *, size_t);
> >  /* Wraps calls to strscpy()/memset(), no arch specific code required */
> >  ssize_t strscpy_pad(char *dest, const char *src, size_t count);
> >  
> > +#define stracpy(to, from)					\
> > +({								\
> > +	size_t size = ARRAY_SIZE(to);				\
> > +	BUILD_BUG_ON(!__same_type(typeof(*to), char));		\
> > +								\
> > +	strscpy(to, from, size);				\
> > +})
> > +
> > +#define stracpy_pad(to, from)					\
> > +({								\
> > +	size_t size = ARRAY_SIZE(to);				\
> > +	BUILD_BUG_ON(!__same_type(typeof(*to), char));		\
> > +								\
> > +	strscpy_pad(to, from, size);				\
> > +})
> > +
> >  #ifndef __HAVE_ARCH_STRCAT
> >  extern char * strcat(char *, const char *);
> >  #endif
> 
> This seems like a reasonable addition, yes. I think Coccinelle might
> actually be able to find all the existing strscpy(dst, src, sizeof(dst))
> cases to jump-start this conversion.

I did that.  It works.  It's a lot of conversions.

$ cat str.cpy.cocci
@@
expression e1;
expression e2;
@@

- strscpy(e1, e2, sizeof(e1))
+ stracpy(e1, e2)

@@
expression e1;
expression e2;
@@

- strlcpy(e1, e2, sizeof(e1))
+ stracpy(e1, e2)

> Devil's advocate: this adds yet more string handling functions... will
> this cause even more confusion?

Documentation is good.
Actual in-kernel use and examples better.
Joe Perches July 22, 2019, 5:58 p.m. UTC | #3
On Mon, 2019-07-22 at 10:43 -0700, Joe Perches wrote:
> On Mon, 2019-07-22 at 10:33 -0700, Kees Cook wrote:
> > On Thu, Jul 04, 2019 at 05:15:57PM -0700, Joe Perches wrote:
> > > On Thu, 2019-07-04 at 13:46 -0700, Joe Perches wrote:
> > > > On Thu, 2019-07-04 at 11:24 +0530, Nitin Gote wrote:
> > > > > Added warnings in checkpatch.pl script to :
> > > > > 
> > > > > 1. Deprecate strcpy() in favor of strscpy().
> > > > > 2. Deprecate strlcpy() in favor of strscpy().
> > > > > 3. Deprecate strncpy() in favor of strscpy() or strscpy_pad().
> > > > > 
> > > > > Updated strncpy() section in Documentation/process/deprecated.rst
> > > > > to cover strscpy_pad() case.
> > > 
> > > []
> > > 
> > > I sent a patch series for some strscpy/strlcpy misuses.
> > > 
> > > How about adding a macro helper to avoid the misuses like:
> > > ---
> > >  include/linux/string.h | 16 ++++++++++++++++
> > >  1 file changed, 16 insertions(+)
> > > 
> > > diff --git a/include/linux/string.h b/include/linux/string.h
> > > index 4deb11f7976b..ef01bd6f19df 100644
> > > --- a/include/linux/string.h
> > > +++ b/include/linux/string.h
> > > @@ -35,6 +35,22 @@ ssize_t strscpy(char *, const char *, size_t);
> > >  /* Wraps calls to strscpy()/memset(), no arch specific code required */
> > >  ssize_t strscpy_pad(char *dest, const char *src, size_t count);
> > >  
> > > +#define stracpy(to, from)					\
> > > +({								\
> > > +	size_t size = ARRAY_SIZE(to);				\
> > > +	BUILD_BUG_ON(!__same_type(typeof(*to), char));		\
> > > +								\
> > > +	strscpy(to, from, size);				\
> > > +})
> > > +
> > > +#define stracpy_pad(to, from)					\
> > > +({								\
> > > +	size_t size = ARRAY_SIZE(to);				\
> > > +	BUILD_BUG_ON(!__same_type(typeof(*to), char));		\
> > > +								\
> > > +	strscpy_pad(to, from, size);				\
> > > +})
> > > +
> > >  #ifndef __HAVE_ARCH_STRCAT
> > >  extern char * strcat(char *, const char *);
> > >  #endif
> > 
> > This seems like a reasonable addition, yes. I think Coccinelle might
> > actually be able to find all the existing strscpy(dst, src, sizeof(dst))
> > cases to jump-start this conversion.
> 
> I did that.  It works.  It's a lot of conversions.
> 
> $ cat str.cpy.cocci
> @@
> expression e1;
> expression e2;
> @@
> 
> - strscpy(e1, e2, sizeof(e1))
> + stracpy(e1, e2)
> 
> @@
> expression e1;
> expression e2;
> @@
> 
> - strlcpy(e1, e2, sizeof(e1))
> + stracpy(e1, e2)
> 
> > Devil's advocate: this adds yet more string handling functions... will
> > this cause even more confusion?
> 
> Documentation is good.
> Actual in-kernel use and examples better.

btw: I just ran this again and it produces:

$ spatch --in-place -sp-file str.cpy.cocci .
$ git checkout tools/
$ git diff --shortstat
 958 files changed, 2179 insertions(+), 2655 deletions(-)
Kees Cook July 22, 2019, 6:21 p.m. UTC | #4
On Mon, Jul 22, 2019 at 10:58:15AM -0700, Joe Perches wrote:
> On Mon, 2019-07-22 at 10:43 -0700, Joe Perches wrote:
> > On Mon, 2019-07-22 at 10:33 -0700, Kees Cook wrote:
> > > On Thu, Jul 04, 2019 at 05:15:57PM -0700, Joe Perches wrote:
> > > > On Thu, 2019-07-04 at 13:46 -0700, Joe Perches wrote:
> > > > > On Thu, 2019-07-04 at 11:24 +0530, Nitin Gote wrote:
> > > > > > Added warnings in checkpatch.pl script to :
> > > > > > 
> > > > > > 1. Deprecate strcpy() in favor of strscpy().
> > > > > > 2. Deprecate strlcpy() in favor of strscpy().
> > > > > > 3. Deprecate strncpy() in favor of strscpy() or strscpy_pad().
> > > > > > 
> > > > > > Updated strncpy() section in Documentation/process/deprecated.rst
> > > > > > to cover strscpy_pad() case.
> > > > 
> > > > []
> > > > 
> > > > I sent a patch series for some strscpy/strlcpy misuses.
> > > > 
> > > > How about adding a macro helper to avoid the misuses like:
> > > > ---
> > > >  include/linux/string.h | 16 ++++++++++++++++
> > > >  1 file changed, 16 insertions(+)
> > > > 
> > > > diff --git a/include/linux/string.h b/include/linux/string.h
> > > > index 4deb11f7976b..ef01bd6f19df 100644
> > > > --- a/include/linux/string.h
> > > > +++ b/include/linux/string.h
> > > > @@ -35,6 +35,22 @@ ssize_t strscpy(char *, const char *, size_t);
> > > >  /* Wraps calls to strscpy()/memset(), no arch specific code required */
> > > >  ssize_t strscpy_pad(char *dest, const char *src, size_t count);
> > > >  
> > > > +#define stracpy(to, from)					\
> > > > +({								\
> > > > +	size_t size = ARRAY_SIZE(to);				\
> > > > +	BUILD_BUG_ON(!__same_type(typeof(*to), char));		\
> > > > +								\
> > > > +	strscpy(to, from, size);				\
> > > > +})
> > > > +
> > > > +#define stracpy_pad(to, from)					\
> > > > +({								\
> > > > +	size_t size = ARRAY_SIZE(to);				\
> > > > +	BUILD_BUG_ON(!__same_type(typeof(*to), char));		\
> > > > +								\
> > > > +	strscpy_pad(to, from, size);				\
> > > > +})
> > > > +
> > > >  #ifndef __HAVE_ARCH_STRCAT
> > > >  extern char * strcat(char *, const char *);
> > > >  #endif
> > > 
> > > This seems like a reasonable addition, yes. I think Coccinelle might
> > > actually be able to find all the existing strscpy(dst, src, sizeof(dst))
> > > cases to jump-start this conversion.
> > 
> > I did that.  It works.  It's a lot of conversions.
> > 
> > $ cat str.cpy.cocci
> > @@
> > expression e1;
> > expression e2;
> > @@
> > 
> > - strscpy(e1, e2, sizeof(e1))
> > + stracpy(e1, e2)
> > 
> > @@
> > expression e1;
> > expression e2;
> > @@
> > 
> > - strlcpy(e1, e2, sizeof(e1))
> > + stracpy(e1, e2)
> > 
> > > Devil's advocate: this adds yet more string handling functions... will
> > > this cause even more confusion?
> > 
> > Documentation is good.
> > Actual in-kernel use and examples better.
> 
> btw: I just ran this again and it produces:
> 
> $ spatch --in-place -sp-file str.cpy.cocci .
> $ git checkout tools/
> $ git diff --shortstat
>  958 files changed, 2179 insertions(+), 2655 deletions(-)

Cool. Well, assuming no one hates this, let's do it. :) Can you send a
more complete patch with docs, etc? Maybe Linus will take it for late
in the next merge window, perhaps?
Matthew Wilcox July 22, 2019, 6:27 p.m. UTC | #5
On Mon, Jul 22, 2019 at 10:58:15AM -0700, Joe Perches wrote:
> On Mon, 2019-07-22 at 10:43 -0700, Joe Perches wrote:
> > On Mon, 2019-07-22 at 10:33 -0700, Kees Cook wrote:
> > > On Thu, Jul 04, 2019 at 05:15:57PM -0700, Joe Perches wrote:
> > > > On Thu, 2019-07-04 at 13:46 -0700, Joe Perches wrote:
> > > > > On Thu, 2019-07-04 at 11:24 +0530, Nitin Gote wrote:
> > > > > > Added warnings in checkpatch.pl script to :
> > > > > > 
> > > > > > 1. Deprecate strcpy() in favor of strscpy().
> > > > > > 2. Deprecate strlcpy() in favor of strscpy().
> > > > > > 3. Deprecate strncpy() in favor of strscpy() or strscpy_pad().
> > > > > > 
> > > > > > Updated strncpy() section in Documentation/process/deprecated.rst
> > > > > > to cover strscpy_pad() case.
> > > > 
> > > > []
> > > > 
> > > > I sent a patch series for some strscpy/strlcpy misuses.
> > > > 
> > > > How about adding a macro helper to avoid the misuses like:
> > > > ---
> > > >  include/linux/string.h | 16 ++++++++++++++++
> > > >  1 file changed, 16 insertions(+)
> > > > 
> > > > diff --git a/include/linux/string.h b/include/linux/string.h
> > > > index 4deb11f7976b..ef01bd6f19df 100644
> > > > --- a/include/linux/string.h
> > > > +++ b/include/linux/string.h
> > > > @@ -35,6 +35,22 @@ ssize_t strscpy(char *, const char *, size_t);
> > > >  /* Wraps calls to strscpy()/memset(), no arch specific code required */
> > > >  ssize_t strscpy_pad(char *dest, const char *src, size_t count);
> > > >  
> > > > +#define stracpy(to, from)					\
> > > > +({								\
> > > > +	size_t size = ARRAY_SIZE(to);				\
> > > > +	BUILD_BUG_ON(!__same_type(typeof(*to), char));		\
> > > > +								\
> > > > +	strscpy(to, from, size);				\
> > > > +})

Where does the 'a' in 'stracpy' come from?  Googling around finds other
people using a function called stracpy, but it takes different arguments.
http://stracpy.blogspot.com/ takes a size argument, as does
https://docs.polserver.com/doxygen/html/d5/dce/stracpy_8cpp_source.html

The one in the 'Links' webbrowser (can't find a link to its source) seems
like a strdup clone.
Joe Perches July 22, 2019, 6:35 p.m. UTC | #6
On Mon, 2019-07-22 at 11:27 -0700, Matthew Wilcox wrote:
> On Mon, Jul 22, 2019 at 10:58:15AM -0700, Joe Perches wrote:
> > On Mon, 2019-07-22 at 10:43 -0700, Joe Perches wrote:
> > > On Mon, 2019-07-22 at 10:33 -0700, Kees Cook wrote:
> > > > On Thu, Jul 04, 2019 at 05:15:57PM -0700, Joe Perches wrote:
> > > > > On Thu, 2019-07-04 at 13:46 -0700, Joe Perches wrote:
[]
> > > > > +#define stracpy(to, from)					\
> > > > > +({								\
> > > > > +	size_t size = ARRAY_SIZE(to);				\
> > > > > +	BUILD_BUG_ON(!__same_type(typeof(*to), char));		\
> > > > > +								\
> > > > > +	strscpy(to, from, size);				\
> > > > > +})
> 
> Where does the 'a' in 'stracpy' come from?

No place in particular.

I used it because dst has to be an 'a'rray rather
than a pointer.

Patch
diff mbox series

diff --git a/include/linux/string.h b/include/linux/string.h
index 4deb11f7976b..ef01bd6f19df 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -35,6 +35,22 @@  ssize_t strscpy(char *, const char *, size_t);
 /* Wraps calls to strscpy()/memset(), no arch specific code required */
 ssize_t strscpy_pad(char *dest, const char *src, size_t count);
 
+#define stracpy(to, from)					\
+({								\
+	size_t size = ARRAY_SIZE(to);				\
+	BUILD_BUG_ON(!__same_type(typeof(*to), char));		\
+								\
+	strscpy(to, from, size);				\
+})
+
+#define stracpy_pad(to, from)					\
+({								\
+	size_t size = ARRAY_SIZE(to);				\
+	BUILD_BUG_ON(!__same_type(typeof(*to), char));		\
+								\
+	strscpy_pad(to, from, size);				\
+})
+
 #ifndef __HAVE_ARCH_STRCAT
 extern char * strcat(char *, const char *);
 #endif