[PATCH -next v3] cifsd: check return value of ksmbd_vfs_getcasexattr() correctly

[PATCH -next v3] cifsd: check return value of ksmbd_vfs_getcasexattr() correctly

[Yang Yingliang]

If ksmbd_vfs_getcasexattr() returns -ENOMEM, stream_buf is NULL,
it will cause null-ptr-deref when using it to copy memory. So we
need check the return value of ksmbd_vfs_getcasexattr() by comparing
with 0.

Fixes: f44158485826 ("cifsd: add file operations")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
v3:
  Handle the 0 return value in ksmbd_vfs_getcasexattr().

v2:
  Handle the case ksmbd_vfs_getcasexattr() returns 0.
---
 fs/cifsd/vfs.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/fs/cifsd/vfs.c b/fs/cifsd/vfs.c
index 97d5584ec870..a56ec1f7f941 100644
--- a/fs/cifsd/vfs.c
+++ b/fs/cifsd/vfs.c
@@ -266,7 +266,7 @@ static ssize_t ksmbd_vfs_getcasexattr(struct dentry *dentry, char *attr_name,
 
 out:
 	kvfree(xattr_list);
-	return value_len;
+	return value_len == 0 ? -ENOENT : value_len;
 }
 
 static int ksmbd_vfs_stream_read(struct ksmbd_file *fp, char *buf, loff_t *pos,
@@ -274,7 +274,6 @@ static int ksmbd_vfs_stream_read(struct ksmbd_file *fp, char *buf, loff_t *pos,
 {
 	ssize_t v_len;
 	char *stream_buf = NULL;
-	int err;
 
 	ksmbd_debug(VFS, "read stream data pos : %llu, count : %zd\n",
 		    *pos, count);
@@ -283,10 +282,9 @@ static int ksmbd_vfs_stream_read(struct ksmbd_file *fp, char *buf, loff_t *pos,
 				       fp->stream.name,
 				       fp->stream.size,
 				       &stream_buf);
-	if (v_len == -ENOENT) {
+	if ((int)v_len < 0) {
 		ksmbd_err("not found stream in xattr : %zd\n", v_len);
-		err = -ENOENT;
-		return err;
+		return (int)v_len;
 	}
 
 	memcpy(buf, &stream_buf[*pos], count);
@@ -415,9 +413,9 @@ static int ksmbd_vfs_stream_write(struct ksmbd_file *fp, char *buf, loff_t *pos,
 				       fp->stream.name,
 				       fp->stream.size,
 				       &stream_buf);
-	if (v_len == -ENOENT) {
+	if ((int)v_len < 0) {
 		ksmbd_err("not found stream in xattr : %zd\n", v_len);
-		err = -ENOENT;
+		err = (int)v_len;
 		goto out;
 	}
 
-- 
2.25.1

Re: [PATCH -next v3] cifsd: check return value of ksmbd_vfs_getcasexattr() correctly

[Hyunchul Lee]

This looks good to me.

2021년 5월 31일 (월) 오후 3:19, Yang Yingliang <yangyingliang@huawei.com>님이 작성:
>
> If ksmbd_vfs_getcasexattr() returns -ENOMEM, stream_buf is NULL,
> it will cause null-ptr-deref when using it to copy memory. So we
> need check the return value of ksmbd_vfs_getcasexattr() by comparing
> with 0.
>
> Fixes: f44158485826 ("cifsd: add file operations")
> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
> ---
> v3:
>   Handle the 0 return value in ksmbd_vfs_getcasexattr().
>
> v2:
>   Handle the case ksmbd_vfs_getcasexattr() returns 0.
> ---
>  fs/cifsd/vfs.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/fs/cifsd/vfs.c b/fs/cifsd/vfs.c
> index 97d5584ec870..a56ec1f7f941 100644
> --- a/fs/cifsd/vfs.c
> +++ b/fs/cifsd/vfs.c
> @@ -266,7 +266,7 @@ static ssize_t ksmbd_vfs_getcasexattr(struct dentry *dentry, char *attr_name,
>
>  out:
>         kvfree(xattr_list);
> -       return value_len;
> +       return value_len == 0 ? -ENOENT : value_len;
>  }
>
>  static int ksmbd_vfs_stream_read(struct ksmbd_file *fp, char *buf, loff_t *pos,
> @@ -274,7 +274,6 @@ static int ksmbd_vfs_stream_read(struct ksmbd_file *fp, char *buf, loff_t *pos,
>  {
>         ssize_t v_len;
>         char *stream_buf = NULL;
> -       int err;
>
>         ksmbd_debug(VFS, "read stream data pos : %llu, count : %zd\n",
>                     *pos, count);
> @@ -283,10 +282,9 @@ static int ksmbd_vfs_stream_read(struct ksmbd_file *fp, char *buf, loff_t *pos,
>                                        fp->stream.name,
>                                        fp->stream.size,
>                                        &stream_buf);
> -       if (v_len == -ENOENT) {
> +       if ((int)v_len < 0) {
>                 ksmbd_err("not found stream in xattr : %zd\n", v_len);
> -               err = -ENOENT;
> -               return err;
> +               return (int)v_len;
>         }
>
>         memcpy(buf, &stream_buf[*pos], count);
> @@ -415,9 +413,9 @@ static int ksmbd_vfs_stream_write(struct ksmbd_file *fp, char *buf, loff_t *pos,
>                                        fp->stream.name,
>                                        fp->stream.size,
>                                        &stream_buf);
> -       if (v_len == -ENOENT) {
> +       if ((int)v_len < 0) {
>                 ksmbd_err("not found stream in xattr : %zd\n", v_len);
> -               err = -ENOENT;
> +               err = (int)v_len;
>                 goto out;
>         }
>
> --
> 2.25.1
>


-- 

Thanks,
Hyunchul