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* [PATCH] CIFS: Fix a potencially linear read overflow
@ 2021-08-17 10:27 Len Baker
  2021-08-18  0:28 ` Paulo Alcantara
  2021-08-18 13:21 ` Jeff Layton
  0 siblings, 2 replies; 5+ messages in thread
From: Len Baker @ 2021-08-17 10:27 UTC (permalink / raw)
  To: Steve French, Jeff Layton, Suresh Jayaraman
  Cc: Len Baker, linux-cifs, samba-technical, linux-kernel, Kees Cook,
	linux-hardening

strlcpy() reads the entire source buffer first. This read may exceed the
destination size limit. This is both inefficient and can lead to linear
read overflows if a source string is not NUL-terminated.

Also, the strnlen() call does not avoid the read overflow in the strlcpy
function when a not NUL-terminated string is passed.

So, replace this block by a call to kstrndup() that avoids this type of
overflow and does the same.

Fixes: 066ce6899484d ("cifs: rename cifs_strlcpy_to_host and make it use new functions")
Signed-off-by: Len Baker <len.baker@gmx.com>
---
 fs/cifs/cifs_unicode.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/fs/cifs/cifs_unicode.c b/fs/cifs/cifs_unicode.c
index 9bd03a231032..171ad8b42107 100644
--- a/fs/cifs/cifs_unicode.c
+++ b/fs/cifs/cifs_unicode.c
@@ -358,14 +358,9 @@ cifs_strndup_from_utf16(const char *src, const int maxlen,
 		if (!dst)
 			return NULL;
 		cifs_from_utf16(dst, (__le16 *) src, len, maxlen, codepage,
-			       NO_MAP_UNI_RSVD);
+				NO_MAP_UNI_RSVD);
 	} else {
-		len = strnlen(src, maxlen);
-		len++;
-		dst = kmalloc(len, GFP_KERNEL);
-		if (!dst)
-			return NULL;
-		strlcpy(dst, src, len);
+		dst = kstrndup(src, maxlen, GFP_KERNEL);
 	}

 	return dst;
--
2.25.1


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] CIFS: Fix a potencially linear read overflow
  2021-08-17 10:27 [PATCH] CIFS: Fix a potencially linear read overflow Len Baker
@ 2021-08-18  0:28 ` Paulo Alcantara
  2021-08-18  2:46   ` Steve French
  2021-08-18 13:21 ` Jeff Layton
  1 sibling, 1 reply; 5+ messages in thread
From: Paulo Alcantara @ 2021-08-18  0:28 UTC (permalink / raw)
  To: Len Baker, Steve French, Jeff Layton, Suresh Jayaraman
  Cc: Len Baker, linux-cifs, samba-technical, linux-kernel, Kees Cook,
	linux-hardening

Len Baker <len.baker@gmx.com> writes:

> strlcpy() reads the entire source buffer first. This read may exceed the
> destination size limit. This is both inefficient and can lead to linear
> read overflows if a source string is not NUL-terminated.
>
> Also, the strnlen() call does not avoid the read overflow in the strlcpy
> function when a not NUL-terminated string is passed.
>
> So, replace this block by a call to kstrndup() that avoids this type of
> overflow and does the same.
>
> Fixes: 066ce6899484d ("cifs: rename cifs_strlcpy_to_host and make it use new functions")
> Signed-off-by: Len Baker <len.baker@gmx.com>
> ---
>  fs/cifs/cifs_unicode.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)

Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] CIFS: Fix a potencially linear read overflow
  2021-08-18  0:28 ` Paulo Alcantara
@ 2021-08-18  2:46   ` Steve French
  0 siblings, 0 replies; 5+ messages in thread
From: Steve French @ 2021-08-18  2:46 UTC (permalink / raw)
  To: Paulo Alcantara
  Cc: Len Baker, Steve French, Jeff Layton, Suresh Jayaraman, CIFS,
	samba-technical, LKML, Kees Cook, linux-hardening

tentatively merged into cifs-2.6.git for-next pending testing

On Tue, Aug 17, 2021 at 7:29 PM Paulo Alcantara <pc@cjr.nz> wrote:
>
> Len Baker <len.baker@gmx.com> writes:
>
> > strlcpy() reads the entire source buffer first. This read may exceed the
> > destination size limit. This is both inefficient and can lead to linear
> > read overflows if a source string is not NUL-terminated.
> >
> > Also, the strnlen() call does not avoid the read overflow in the strlcpy
> > function when a not NUL-terminated string is passed.
> >
> > So, replace this block by a call to kstrndup() that avoids this type of
> > overflow and does the same.
> >
> > Fixes: 066ce6899484d ("cifs: rename cifs_strlcpy_to_host and make it use new functions")
> > Signed-off-by: Len Baker <len.baker@gmx.com>
> > ---
> >  fs/cifs/cifs_unicode.c | 9 ++-------
> >  1 file changed, 2 insertions(+), 7 deletions(-)
>
> Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>



-- 
Thanks,

Steve

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] CIFS: Fix a potencially linear read overflow
  2021-08-17 10:27 [PATCH] CIFS: Fix a potencially linear read overflow Len Baker
  2021-08-18  0:28 ` Paulo Alcantara
@ 2021-08-18 13:21 ` Jeff Layton
  2021-08-20  5:58   ` Steve French
  1 sibling, 1 reply; 5+ messages in thread
From: Jeff Layton @ 2021-08-18 13:21 UTC (permalink / raw)
  To: Len Baker, Steve French, Suresh Jayaraman
  Cc: linux-cifs, samba-technical, linux-kernel, Kees Cook, linux-hardening

On Tue, 2021-08-17 at 12:27 +0200, Len Baker wrote:
> strlcpy() reads the entire source buffer first. This read may exceed the
> destination size limit. This is both inefficient and can lead to linear
> read overflows if a source string is not NUL-terminated.
> 
> Also, the strnlen() call does not avoid the read overflow in the strlcpy
> function when a not NUL-terminated string is passed.
> 
> So, replace this block by a call to kstrndup() that avoids this type of
> overflow and does the same.
> 
> Fixes: 066ce6899484d ("cifs: rename cifs_strlcpy_to_host and make it use new functions")
> Signed-off-by: Len Baker <len.baker@gmx.com>
> ---
>  fs/cifs/cifs_unicode.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/cifs/cifs_unicode.c b/fs/cifs/cifs_unicode.c
> index 9bd03a231032..171ad8b42107 100644
> --- a/fs/cifs/cifs_unicode.c
> +++ b/fs/cifs/cifs_unicode.c
> @@ -358,14 +358,9 @@ cifs_strndup_from_utf16(const char *src, const int maxlen,
>  		if (!dst)
>  			return NULL;
>  		cifs_from_utf16(dst, (__le16 *) src, len, maxlen, codepage,
> -			       NO_MAP_UNI_RSVD);
> +				NO_MAP_UNI_RSVD);
>  	} else {
> -		len = strnlen(src, maxlen);
> -		len++;
> -		dst = kmalloc(len, GFP_KERNEL);
> -		if (!dst)
> -			return NULL;
> -		strlcpy(dst, src, len);
> +		dst = kstrndup(src, maxlen, GFP_KERNEL);
>  	}
> 
>  	return dst;
> --
> 2.25.1
> 

Reviewed-by: Jeff Layton <jlayton@kernel.org>


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] CIFS: Fix a potencially linear read overflow
  2021-08-18 13:21 ` Jeff Layton
@ 2021-08-20  5:58   ` Steve French
  0 siblings, 0 replies; 5+ messages in thread
From: Steve French @ 2021-08-20  5:58 UTC (permalink / raw)
  To: Jeff Layton
  Cc: Len Baker, Steve French, Suresh Jayaraman, CIFS, samba-technical,
	LKML, Kees Cook, linux-hardening

Added RB and repushed to cifs-2.6.git for-next

On Wed, Aug 18, 2021 at 8:22 AM Jeff Layton <jlayton@kernel.org> wrote:
>
> On Tue, 2021-08-17 at 12:27 +0200, Len Baker wrote:
> > strlcpy() reads the entire source buffer first. This read may exceed the
> > destination size limit. This is both inefficient and can lead to linear
> > read overflows if a source string is not NUL-terminated.
> >
> > Also, the strnlen() call does not avoid the read overflow in the strlcpy
> > function when a not NUL-terminated string is passed.
> >
> > So, replace this block by a call to kstrndup() that avoids this type of
> > overflow and does the same.
> >
> > Fixes: 066ce6899484d ("cifs: rename cifs_strlcpy_to_host and make it use new functions")
> > Signed-off-by: Len Baker <len.baker@gmx.com>
> > ---
> >  fs/cifs/cifs_unicode.c | 9 ++-------
> >  1 file changed, 2 insertions(+), 7 deletions(-)
> >
> > diff --git a/fs/cifs/cifs_unicode.c b/fs/cifs/cifs_unicode.c
> > index 9bd03a231032..171ad8b42107 100644
> > --- a/fs/cifs/cifs_unicode.c
> > +++ b/fs/cifs/cifs_unicode.c
> > @@ -358,14 +358,9 @@ cifs_strndup_from_utf16(const char *src, const int maxlen,
> >               if (!dst)
> >                       return NULL;
> >               cifs_from_utf16(dst, (__le16 *) src, len, maxlen, codepage,
> > -                            NO_MAP_UNI_RSVD);
> > +                             NO_MAP_UNI_RSVD);
> >       } else {
> > -             len = strnlen(src, maxlen);
> > -             len++;
> > -             dst = kmalloc(len, GFP_KERNEL);
> > -             if (!dst)
> > -                     return NULL;
> > -             strlcpy(dst, src, len);
> > +             dst = kstrndup(src, maxlen, GFP_KERNEL);
> >       }
> >
> >       return dst;
> > --
> > 2.25.1
> >
>
> Reviewed-by: Jeff Layton <jlayton@kernel.org>
>


-- 
Thanks,

Steve

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2021-08-20  5:59 UTC | newest]

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2021-08-17 10:27 [PATCH] CIFS: Fix a potencially linear read overflow Len Baker
2021-08-18  0:28 ` Paulo Alcantara
2021-08-18  2:46   ` Steve French
2021-08-18 13:21 ` Jeff Layton
2021-08-20  5:58   ` Steve French

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