[PATCH] cifs: smb2ops: Fix NULL check in smb2_query_symlink

[PATCH] cifs: smb2ops: Fix NULL check in smb2_query_symlink

[Gustavo A. R. Silva]

The current code null checks variable err_buf, which is always null
when it is checked, hence utf16_path is free'd and the function
returns -ENOENT everytime it is called, making it impossible for the
execution path to reach the following code:

err_buf = err_iov.iov_base;

Fix this by null checking err_iov.iov_base instead of err_buf. Also,
notice that err_buf no longer needs to be initialized to NULL.

Addresses-Coverity-ID: 1467876 ("Logically dead code")
Fixes: 2d636199e400 ("cifs: Change SMB2_open to return an iov for the error parameter")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 fs/cifs/smb2ops.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index b4ae932..38ebf3f 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -1452,7 +1452,7 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
 	struct cifs_open_parms oparms;
 	struct cifs_fid fid;
 	struct kvec err_iov = {NULL, 0};
-	struct smb2_err_rsp *err_buf = NULL;
+	struct smb2_err_rsp *err_buf;
 	struct smb2_symlink_err_rsp *symlink;
 	unsigned int sub_len;
 	unsigned int sub_offset;
@@ -1476,7 +1476,7 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
 
 	rc = SMB2_open(xid, &oparms, utf16_path, &oplock, NULL, &err_iov);
 
-	if (!rc || !err_buf) {
+	if (!rc || !err_iov.iov_base) {
 		kfree(utf16_path);
 		return -ENOENT;
 	}
-- 
2.7.4

Re: [PATCH] cifs: smb2ops: Fix NULL check in smb2_query_symlink

[Pavel Shilovsky]

2018-04-13 8:13 GMT-07:00 Gustavo A. R. Silva <gustavo@embeddedor.com>:
> The current code null checks variable err_buf, which is always null
> when it is checked, hence utf16_path is free'd and the function
> returns -ENOENT everytime it is called, making it impossible for the
> execution path to reach the following code:
>
> err_buf = err_iov.iov_base;
>
> Fix this by null checking err_iov.iov_base instead of err_buf. Also,
> notice that err_buf no longer needs to be initialized to NULL.
>
> Addresses-Coverity-ID: 1467876 ("Logically dead code")
> Fixes: 2d636199e400 ("cifs: Change SMB2_open to return an iov for the error parameter")
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>  fs/cifs/smb2ops.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> index b4ae932..38ebf3f 100644
> --- a/fs/cifs/smb2ops.c
> +++ b/fs/cifs/smb2ops.c
> @@ -1452,7 +1452,7 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
>         struct cifs_open_parms oparms;
>         struct cifs_fid fid;
>         struct kvec err_iov = {NULL, 0};
> -       struct smb2_err_rsp *err_buf = NULL;
> +       struct smb2_err_rsp *err_buf;
>         struct smb2_symlink_err_rsp *symlink;
>         unsigned int sub_len;
>         unsigned int sub_offset;
> @@ -1476,7 +1476,7 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
>
>         rc = SMB2_open(xid, &oparms, utf16_path, &oplock, NULL, &err_iov);
>
> -       if (!rc || !err_buf) {
> +       if (!rc || !err_iov.iov_base) {
>                 kfree(utf16_path);
>                 return -ENOENT;
>         }
> --
> 2.7.4
>
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Thanks!

Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>

--
Best regards,
Pavel Shilovsky