Re: [PATCH v2] vfs/xattr: mm/shmem: kernfs: release simple xattr entry in a right way

[Hugh Dickins <hughd@google.com>]

On Sat, 4 Jul 2020, Chengguang Xu wrote:

> After commit fdc85222d58e ("kernfs: kvmalloc xattr value
> instead of kmalloc"), simple xattr entry is allocated with
> kvmalloc() instead of kmalloc(), so we should release it
> with kvfree() instead of kfree().
> 
> Cc: stable@vger.kernel.org # v5.7
> Cc: Daniel Xu <dxu@dxuuu.xyz>
> Cc: Chris Down <chris@chrisdown.name>
> Cc: Andreas Dilger <adilger@dilger.ca>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Cc: Hugh Dickins <hughd@google.com>
> Fixes: fdc85222d58e ("kernfs: kvmalloc xattr value instead of kmalloc")
> Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>

Good catch, thank you:
Acked-by: Hugh Dickins <hughd@google.com>

> ---
> v1->v2:
> - Fix freeing issue in simple_xattrs_free().
> - Change patch subject.
> 
>  include/linux/xattr.h | 3 ++-
>  mm/shmem.c            | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/xattr.h b/include/linux/xattr.h
> index 47eaa34f8761..c5afaf8ca7a2 100644
> --- a/include/linux/xattr.h
> +++ b/include/linux/xattr.h
> @@ -15,6 +15,7 @@
>  #include <linux/slab.h>
>  #include <linux/types.h>
>  #include <linux/spinlock.h>
> +#include <linux/mm.h>
>  #include <uapi/linux/xattr.h>
>  
>  struct inode;
> @@ -94,7 +95,7 @@ static inline void simple_xattrs_free(struct simple_xattrs *xattrs)
>  
>  	list_for_each_entry_safe(xattr, node, &xattrs->head, list) {
>  		kfree(xattr->name);
> -		kfree(xattr);
> +		kvfree(xattr);
>  	}
>  }
>  
> diff --git a/mm/shmem.c b/mm/shmem.c
> index a0dbe62f8042..b2abca3f7f33 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -3178,7 +3178,7 @@ static int shmem_initxattrs(struct inode *inode,
>  		new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
>  					  GFP_KERNEL);
>  		if (!new_xattr->name) {
> -			kfree(new_xattr);
> +			kvfree(new_xattr);
>  			return -ENOMEM;
>  		}
>  
> -- 
> 2.20.1
> 
> 
> 
>