Re: [PATCH][CIFS] Fix uninitialized pointer access to dacl_ptr in build_sec_desc

["Aurélien Aptel" <aaptel@suse.com>]

Steve French <smfrench@gmail.com> writes:

>     smb3: fix possible access to uninitialized pointer to DACL
>
>     dacl_ptr can be null so we must check for it (ie if dacloffset is
> set) everywhere dacl_ptr is
>     used in build_sec_desc - and we were missing one check
>
>     Addresses-Coverity: 1475598 ("Explicit null dereference")

Looks OK since dacl_ptr is only set if dacloffset is set but it would
be clearer if you check for dacl_ptr directly no? Any reason you are
checking this way?

I think this is clearer, unless I'm missing something:

ndacl_ptr->num_aces = dacl_ptr ? dacl_ptr->num_aces : 0;


>
>
> -- 
> Thanks,
>
> Steve
> From ec06cb04376e5abc927a9b85dd768ce8728965bb Mon Sep 17 00:00:00 2001
> From: Steve French <stfrench@microsoft.com>
> Date: Tue, 22 Jun 2021 17:54:50 -0500
> Subject: [PATCH] smb3: fix possible access to uninitialized pointer to DACL
>
> dacl_ptr can be null so we must check for it everywhere it is
> used in build_sec_desc.
>
> Addresses-Coverity: 1475598 ("Explicit null dereference")
> Signed-off-by: Steve French <stfrench@microsoft.com>
> ---
>  fs/cifs/cifsacl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/cifs/cifsacl.c b/fs/cifs/cifsacl.c
> index 784407f9280f..25a8139336fa 100644
> --- a/fs/cifs/cifsacl.c
> +++ b/fs/cifs/cifsacl.c
> @@ -1308,7 +1308,7 @@ static int build_sec_desc(struct cifs_ntsd *pntsd, struct cifs_ntsd *pnntsd,
>  		ndacl_ptr = (struct cifs_acl *)((char *)pnntsd + ndacloffset);
>  		ndacl_ptr->revision =
>  			dacloffset ? dacl_ptr->revision : cpu_to_le16(ACL_REVISION);
> -		ndacl_ptr->num_aces = dacl_ptr->num_aces;
> +		ndacl_ptr->num_aces = dacloffset ? dacl_ptr->num_aces : 0;
>  
>  		if (uid_valid(uid)) { /* chown */
>  			uid_t id;
> -- 
> 2.30.2
>

-- 
Aurélien Aptel / SUSE Labs Samba Team
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