Re: [PATCH1/1]sqfs: sqfs_tokenize() should fill the tokens list instead of free items

Re: [PATCH1/1]sqfs: sqfs_tokenize() should fill the tokens list instead of free items

[jc.w4ng]

[PATCH1/1]sqfs: sqfs_tokenize() should fill the tokens list instead of free items

[Jincheng Wang]

We can delete two lines of code to avoid double free bug, but still a wild
pointers bug.

A test for wild pointers:
    sqfsls host 0  1//2/3//4/5

Fill the tokens list can solve it well.


Signed-off-by: Jincheng Wang <jc.w4ng@gmail.com>
---
 fs/squashfs/sqfs.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/squashfs/sqfs.c b/fs/squashfs/sqfs.c
index e2d91c654c..50d3f8b71e 100644
--- a/fs/squashfs/sqfs.c
+++ b/fs/squashfs/sqfs.c
@@ -303,8 +303,9 @@ static int sqfs_tokenize(char **tokens, int count,
const char *str)
  aux = strtok(!j ? strc : NULL, "/");
  tokens[j] = strdup(aux);
  if (!tokens[j]) {
- for (i = 0; i < j; i++)
- free(tokens[i]);
+ /* fill tokens list to avoid wild pointers being freed*/
+ for (i = j + 1; i < count; i++)
+ tokens[i] = 0;
  ret = -ENOMEM;
  goto free_strc;
  }
-- 
2.27.0

Re: [PATCH1/1]sqfs: sqfs_tokenize() should fill the tokens list instead of free items

[Tom Rini]

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On Sat, Oct 16, 2021 at 10:19:48AM +0800, Jincheng Wang wrote:

> We can delete two lines of code to avoid double free bug, but still a wild
> pointers bug.
> 
> A test for wild pointers:
>     sqfsls host 0  1//2/3//4/5
> 
> Fill the tokens list can solve it well.
> 
> 
> Signed-off-by: Jincheng Wang <jc.w4ng@gmail.com>
> ---
>  fs/squashfs/sqfs.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
>   }
> 
> diff --git a/fs/squashfs/sqfs.c b/fs/squashfs/sqfs.c
> index e2d91c654c..50d3f8b71e 100644
> --- a/fs/squashfs/sqfs.c
> +++ b/fs/squashfs/sqfs.c
> @@ -303,8 +303,9 @@ static int sqfs_tokenize(char **tokens, int count,
> const char *str)
>   aux = strtok(!j ? strc : NULL, "/");
>   tokens[j] = strdup(aux);
>   if (!tokens[j]) {
> - for (i = 0; i < j; i++)
> - free(tokens[i]);
> + /* fill tokens list to avoid wild pointers being freed*/
> + for (i = j + 1; i < count; i++)
> + tokens[i] = 0;
>   ret = -ENOMEM;
>   goto free_strc;

Aside from the whitespace having been destroyed, any comments from the
maintainers / reviewers?  Thanks!

-- 
Tom

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Re: [PATCH1/1]sqfs: sqfs_tokenize() should fill the tokens list instead of free items

[Miquel Raynal]

Hello,

trini@konsulko.com wrote on Tue, 26 Oct 2021 15:25:56 -0400:

> On Sat, Oct 16, 2021 at 10:19:48AM +0800, Jincheng Wang wrote:
> 
> > We can delete two lines of code to avoid double free bug, but still a wild
> > pointers bug.
> > 
> > A test for wild pointers:
> >     sqfsls host 0  1//2/3//4/5
> > 
> > Fill the tokens list can solve it well.
> > 
> > 
> > Signed-off-by: Jincheng Wang <jc.w4ng@gmail.com>
> > ---
> >  fs/squashfs/sqfs.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> >   }
> > 
> > diff --git a/fs/squashfs/sqfs.c b/fs/squashfs/sqfs.c
> > index e2d91c654c..50d3f8b71e 100644
> > --- a/fs/squashfs/sqfs.c
> > +++ b/fs/squashfs/sqfs.c
> > @@ -303,8 +303,9 @@ static int sqfs_tokenize(char **tokens, int count,
> > const char *str)
> >   aux = strtok(!j ? strc : NULL, "/");
> >   tokens[j] = strdup(aux);
> >   if (!tokens[j]) {
> > - for (i = 0; i < j; i++)
> > - free(tokens[i]);

Where is the double free here? Why do you stop freeing the tokens list?

> > + /* fill tokens list to avoid wild pointers being freed*/
> > + for (i = j + 1; i < count; i++)
> > + tokens[i] = 0;

This does not feel right. Perhaps it's just me not getting through the
lack of spacing successfully but this deserves more explanations.

> >   ret = -ENOMEM;
> >   goto free_strc;  
> 
> Aside from the whitespace having been destroyed, any comments from the
> maintainers / reviewers?  Thanks!
> 

Thanks,
Miquèl

Fwd: [PATCH1/1]sqfs: sqfs_tokenize() should fill the tokens list instead of free items

[Jincheng Wang]

---------- Forwarded message ---------
发件人： Jincheng Wang <jc.w4ng@gmail.com>
Date: 2021年10月31日周日 下午6:23
Subject: Re: [PATCH1/1]sqfs: sqfs_tokenize() should fill the tokens list
instead of free items
To: Miquel Raynal <miquel.raynal@bootlin.com>


Hello,

Apologize for a late reply ,and I made a mistake in wirting mail.

Here is the email before I commit the patch.

Double free vulnerability in sqfs commands ("sqfsls" and "sqfsload")

On Tue, Oct 12, 2021 at 04:07:43PM +0800, Jincheng Wang wrote:

> Hello U-Boot lists!
> I had been doing a fuzz testing in U-Boot .
> There is a double free bug in U-Boot, in /fs/squashfs/sqfs.c in the
> function sqfs_tokenize( ).
> On the line 307, tokens[i] is being freed and the ret is being set
-ENOMEM,
> it will go to the out: label and free tokens[i] again (just like
> CVE-2020-8432, double free in do_rename_gpt_parts() ).
> Here is  a sample command cause to crash in sandbox environment:
>     host bind 0 test.sqsh
>     sqfsls host 0 1//3

------------------------------

The vulnerability can be fixed with a new return value and a new label. But
I didn't want to creat  these, I chose another way.

Regards,
Jincheng


Miquel Raynal <miquel.raynal@bootlin.com> 于2021年10月27日周三 下午4:17写道：

> Hello,
>
> trini@konsulko.com wrote on Tue, 26 Oct 2021 15:25:56 -0400:
>
> > On Sat, Oct 16, 2021 at 10:19:48AM +0800, Jincheng Wang wrote:
> >
> > > We can delete two lines of code to avoid double free bug, but still a
> wild
> > > pointers bug.
> > >
> > > A test for wild pointers:
> > >     sqfsls host 0  1//2/3//4/5
> > >
> > > Fill the tokens list can solve it well.
> > >
> > >
> > > Signed-off-by: Jincheng Wang <jc.w4ng@gmail.com>
> > > ---
> > >  fs/squashfs/sqfs.c | 5 +++--
> > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > >
> > >   }
> > >
> > > diff --git a/fs/squashfs/sqfs.c b/fs/squashfs/sqfs.c
> > > index e2d91c654c..50d3f8b71e 100644
> > > --- a/fs/squashfs/sqfs.c
> > > +++ b/fs/squashfs/sqfs.c
> > > @@ -303,8 +303,9 @@ static int sqfs_tokenize(char **tokens, int count,
> > > const char *str)
> > >   aux = strtok(!j ? strc : NULL, "/");
> > >   tokens[j] = strdup(aux);
> > >   if (!tokens[j]) {
> > > - for (i = 0; i < j; i++)
> > > - free(tokens[i]);
>
> Where is the double free here? Why do you stop freeing the tokens list?
>
> > > + /* fill tokens list to avoid wild pointers being freed*/
> > > + for (i = j + 1; i < count; i++)
> > > + tokens[i] = 0;
>
> This does not feel right. Perhaps it's just me not getting through the
> lack of spacing successfully but this deserves more explanations.
>
> > >   ret = -ENOMEM;
> > >   goto free_strc;
> >
> > Aside from the whitespace having been destroyed, any comments from the
> > maintainers / reviewers?  Thanks!
> >
>
> Thanks,
> Miquèl
>

Re: [PATCH1/1]sqfs: sqfs_tokenize() should fill the tokens list instead of free items

[Miquel Raynal]

Hi Jincheng,

jc.w4ng@gmail.com wrote on Sun, 31 Oct 2021 18:24:47 +0800:

> ---------- Forwarded message ---------
> 发件人： Jincheng Wang <jc.w4ng@gmail.com>
> Date: 2021年10月31日周日 下午6:23
> Subject: Re: [PATCH1/1]sqfs: sqfs_tokenize() should fill the tokens list
> instead of free items
> To: Miquel Raynal <miquel.raynal@bootlin.com>
> 
> 
> Hello,
> 
> Apologize for a late reply ,and I made a mistake in wirting mail.
> 
> Here is the email before I commit the patch.
> 
> Double free vulnerability in sqfs commands ("sqfsls" and "sqfsload")
> 
> On Tue, Oct 12, 2021 at 04:07:43PM +0800, Jincheng Wang wrote:
> 
> > Hello U-Boot lists!
> > I had been doing a fuzz testing in U-Boot .
> > There is a double free bug in U-Boot, in /fs/squashfs/sqfs.c in the
> > function sqfs_tokenize( ).
> > On the line 307, tokens[i] is being freed and the ret is being set  
> -ENOMEM,
> > it will go to the out: label and free tokens[i] again (just like
> > CVE-2020-8432, double free in do_rename_gpt_parts() ).
> > Here is  a sample command cause to crash in sandbox environment:
> >     host bind 0 test.sqsh
> >     sqfsls host 0 1//3  
> 
> ------------------------------
> 
> The vulnerability can be fixed with a new return value and a new label. But
> I didn't want to creat  these, I chose another way.

You need to answer my questions below if you don't want to propose
another solution. But creating a new goto label is perhaps the good way
to solve this, provided that there is actually a leak (I am waiting for
the explanation of how it happens).

Cheers,
Miquèl

> 
> Regards,
> Jincheng
> 
> 
> Miquel Raynal <miquel.raynal@bootlin.com> 于2021年10月27日周三 下午4:17写道：
> 
> > Hello,
> >
> > trini@konsulko.com wrote on Tue, 26 Oct 2021 15:25:56 -0400:
> >  
> > > On Sat, Oct 16, 2021 at 10:19:48AM +0800, Jincheng Wang wrote:
> > >  
> > > > We can delete two lines of code to avoid double free bug, but still a  
> > wild  
> > > > pointers bug.
> > > >
> > > > A test for wild pointers:
> > > >     sqfsls host 0  1//2/3//4/5
> > > >
> > > > Fill the tokens list can solve it well.
> > > >
> > > >
> > > > Signed-off-by: Jincheng Wang <jc.w4ng@gmail.com>
> > > > ---
> > > >  fs/squashfs/sqfs.c | 5 +++--
> > > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > > >
> > > >   }
> > > >
> > > > diff --git a/fs/squashfs/sqfs.c b/fs/squashfs/sqfs.c
> > > > index e2d91c654c..50d3f8b71e 100644
> > > > --- a/fs/squashfs/sqfs.c
> > > > +++ b/fs/squashfs/sqfs.c
> > > > @@ -303,8 +303,9 @@ static int sqfs_tokenize(char **tokens, int count,
> > > > const char *str)
> > > >   aux = strtok(!j ? strc : NULL, "/");
> > > >   tokens[j] = strdup(aux);
> > > >   if (!tokens[j]) {
> > > > - for (i = 0; i < j; i++)
> > > > - free(tokens[i]);  
> >
> > Where is the double free here? Why do you stop freeing the tokens list?
> >  
> > > > + /* fill tokens list to avoid wild pointers being freed*/
> > > > + for (i = j + 1; i < count; i++)
> > > > + tokens[i] = 0;  
> >
> > This does not feel right. Perhaps it's just me not getting through the
> > lack of spacing successfully but this deserves more explanations.
> >  
> > > >   ret = -ENOMEM;
> > > >   goto free_strc;  
> > >
> > > Aside from the whitespace having been destroyed, any comments from the
> > > maintainers / reviewers?  Thanks!
> > >  
> >
> > Thanks,
> > Miquèl
> >