[PATCH] cifs: check pointer before freeing

[PATCH] cifs: check pointer before freeing

[trix]

From: Tom Rix <trix@redhat.com>

clang static analysis reports this problem

dfs_cache.c:591:2: warning: Argument to kfree() is a constant address
  (18446744073709551614), which is not memory allocated by malloc()
        kfree(vi);
        ^~~~~~~~~

In dfs_cache_del_vol() the volume info pointer 'vi' being freed
is the return of a call to find_vol().  The large constant address
is find_vol() returning an error.

Add an error check to dfs_cache_del_vol() similar to the one done
in dfs_cache_update_vol().

Fixes: 54be1f6c1c37 ("cifs: Add DFS cache routines")
Signed-off-by: Tom Rix <trix@redhat.com>
---
 fs/cifs/dfs_cache.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c
index 6ad6ba5f6ebe..0fdb0de7ff86 100644
--- a/fs/cifs/dfs_cache.c
+++ b/fs/cifs/dfs_cache.c
@@ -1260,7 +1260,8 @@ void dfs_cache_del_vol(const char *fullpath)
 	vi = find_vol(fullpath);
 	spin_unlock(&vol_list_lock);
 
-	kref_put(&vi->refcnt, vol_release);
+	if (!IS_ERR(vi))
+		kref_put(&vi->refcnt, vol_release);
 }
 
 /**
-- 
2.27.0

Re: [PATCH] cifs: check pointer before freeing

[Nathan Chancellor]

On Tue, Jan 05, 2021 at 12:21:26PM -0800, trix@redhat.com wrote:
> From: Tom Rix <trix@redhat.com>
> 
> clang static analysis reports this problem
> 
> dfs_cache.c:591:2: warning: Argument to kfree() is a constant address
>   (18446744073709551614), which is not memory allocated by malloc()
>         kfree(vi);
>         ^~~~~~~~~
> 
> In dfs_cache_del_vol() the volume info pointer 'vi' being freed
> is the return of a call to find_vol().  The large constant address
> is find_vol() returning an error.
> 
> Add an error check to dfs_cache_del_vol() similar to the one done
> in dfs_cache_update_vol().
> 
> Fixes: 54be1f6c1c37 ("cifs: Add DFS cache routines")
> Signed-off-by: Tom Rix <trix@redhat.com>

Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>

> ---
>  fs/cifs/dfs_cache.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c
> index 6ad6ba5f6ebe..0fdb0de7ff86 100644
> --- a/fs/cifs/dfs_cache.c
> +++ b/fs/cifs/dfs_cache.c
> @@ -1260,7 +1260,8 @@ void dfs_cache_del_vol(const char *fullpath)
>  	vi = find_vol(fullpath);
>  	spin_unlock(&vol_list_lock);
>  
> -	kref_put(&vi->refcnt, vol_release);
> +	if (!IS_ERR(vi))
> +		kref_put(&vi->refcnt, vol_release);
>  }
>  
>  /**
> -- 
> 2.27.0
> 

Re: [PATCH] cifs: check pointer before freeing

[Steve French]

merged into cifs-2.6.git for-next and added cc:stable

On Tue, Jan 5, 2021 at 5:08 PM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> On Tue, Jan 05, 2021 at 12:21:26PM -0800, trix@redhat.com wrote:
> > From: Tom Rix <trix@redhat.com>
> >
> > clang static analysis reports this problem
> >
> > dfs_cache.c:591:2: warning: Argument to kfree() is a constant address
> >   (18446744073709551614), which is not memory allocated by malloc()
> >         kfree(vi);
> >         ^~~~~~~~~
> >
> > In dfs_cache_del_vol() the volume info pointer 'vi' being freed
> > is the return of a call to find_vol().  The large constant address
> > is find_vol() returning an error.
> >
> > Add an error check to dfs_cache_del_vol() similar to the one done
> > in dfs_cache_update_vol().
> >
> > Fixes: 54be1f6c1c37 ("cifs: Add DFS cache routines")
> > Signed-off-by: Tom Rix <trix@redhat.com>
>
> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
>
> > ---
> >  fs/cifs/dfs_cache.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c
> > index 6ad6ba5f6ebe..0fdb0de7ff86 100644
> > --- a/fs/cifs/dfs_cache.c
> > +++ b/fs/cifs/dfs_cache.c
> > @@ -1260,7 +1260,8 @@ void dfs_cache_del_vol(const char *fullpath)
> >       vi = find_vol(fullpath);
> >       spin_unlock(&vol_list_lock);
> >
> > -     kref_put(&vi->refcnt, vol_release);
> > +     if (!IS_ERR(vi))
> > +             kref_put(&vi->refcnt, vol_release);
> >  }
> >
> >  /**
> > --
> > 2.27.0
> >



-- 
Thanks,

Steve