[lvc-project] [PATCH] smb: remove redundant DACL check in smb_check_perm_dacl

[Fedor Pchelkin]

Префикс подсистемы для fs/smb/server/smbacl.c - это "ksmbd", не "smb".

On Sun, 07. Dec 01:59, Alexey Velichayshiy wrote:
> Problem Analysis:
> 1. Permanently false condition:
> The check `if (!pdacl->num_aces)` after the
> `FILE_MAXIMAL_ACCESS_LE` block can never execute because when
> `pdacl->num_aces == 0`, the function already jumps to `err_out`
> in the earlier DACL validation check that precedes it.
> 
> 2. Logical contradiction:
> The code contains conflicting semantics for empty DACL handling:
> 	- First check (before FILE_MAXIMAL_ACCESS_LE block):
> 	Empty DACL → access denied → goto err_out.
> 	- Second check (after FILE_MAXIMAL_ACCESS_LE block):
> 	Empty DACL → grant GENERIC_ALL_FLAGS.
> This creates unreachable code and semantic inconsistency.
> 
> Solution:
> Remove the unreachable code block as the most
> concise solution with no functional impact.

Это трудночитаемый текст с лишними для понимания проблемы выкладками,
правда.  Сравните, например, с такой постановкой проблемы и кратким итогом
по предлагаемому исправлению:

A zero value of pdacl->num_aces is already handled at the start of
smb_check_perm_dacl() so the second check is useless.

Drop the unreachable code block, no functional impact intended.

И всё :)

> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Alexey Velichayshiy <a.velichayshiy at ispras.ru>
> ---

С учетом замечаний выше предлагаю отправлять, спасибо!

>  fs/smb/server/smbacl.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/fs/smb/server/smbacl.c b/fs/smb/server/smbacl.c
> index 5aa7a66334d9..05598d994a68 100644
> --- a/fs/smb/server/smbacl.c
> +++ b/fs/smb/server/smbacl.c
> @@ -1307,9 +1307,6 @@ int smb_check_perm_dacl(struct ksmbd_conn *conn, const struct path *path,
>  			granted |= le32_to_cpu(ace->access_req);
>  			ace = (struct smb_ace *)((char *)ace + le16_to_cpu(ace->size));
>  		}
> -
> -		if (!pdacl->num_aces)
> -			granted = GENERIC_ALL_FLAGS;
>  	}
>  
>  	if (!uid)
> -- 
> 2.43.0