[PATCH] remove invalid reference to list iterator variable

[PATCH] remove invalid reference to list iterator variable

[Julia Lawall]

If list_for_each_entry, etc complete a traversal of the list, the iterator
variable ends up pointing to an address at an offset from the list head,
and not a meaningful structure.  Thus this value should not be used after
the end of the iterator.

The complete semantic match that finds this problem is:
(http://coccinelle.lip6.fr/)

@@
identifier c,member;
expression E,x;
iterator name list_for_each_entry;
iterator name list_for_each_entry_reverse;
iterator name list_for_each_entry_continue;
iterator name list_for_each_entry_continue_reverse;
iterator name list_for_each_entry_from;
iterator name list_for_each_entry_safe;
iterator name list_for_each_entry_safe_continue;
iterator name list_for_each_entry_safe_from;
iterator name list_for_each_entry_safe_reverse;
iterator name hlist_for_each_entry;
iterator name hlist_for_each_entry_continue;
iterator name hlist_for_each_entry_from;
iterator name hlist_for_each_entry_safe;
statement S;
@@

(
list_for_each_entry(c,...,member) { ... when != break;
                                 when forall
                                 when strict
}
|
list_for_each_entry_reverse(c,...,member) { ... when != break;
                                 when forall
                                 when strict
}
|
list_for_each_entry_continue(c,...,member) { ... when != break;
                                 when forall
                                 when strict
}
|
list_for_each_entry_continue_reverse(c,...,member) { ... when != break;
                                 when forall
                                 when strict
}
|
list_for_each_entry_from(c,...,member) { ... when != break;
                                 when forall
                                 when strict
}
|
list_for_each_entry_safe(c,...,member) { ... when != break;
                                 when forall
                                 when strict
}
|
list_for_each_entry_safe_continue(c,...,member) { ... when != break;
                                 when forall
                                 when strict
}
|
list_for_each_entry_safe_from(c,...,member) { ... when != break;
                                 when forall
                                 when strict
}
|
list_for_each_entry_safe_reverse(c,...,member) { ... when != break;
                                 when forall
                                 when strict
}
)
...
(
list_for_each_entry(c,...) S
|
list_for_each_entry_reverse(c,...) S
|
list_for_each_entry_continue(c,...) S
|
list_for_each_entry_continue_reverse(c,...) S
|
list_for_each_entry_from(c,...) S
|
list_for_each_entry_safe(c,...) S
|
list_for_each_entry_safe(x,c,...) S
|
list_for_each_entry_safe_continue(c,...) S
|
list_for_each_entry_safe_continue(x,c,...) S
|
list_for_each_entry_safe_from(c,...) S
|
list_for_each_entry_safe_from(x,c,...) S
|
list_for_each_entry_safe_reverse(c,...) S
|
list_for_each_entry_safe_reverse(x,c,...) S
|
hlist_for_each_entry(c,...) S
|
hlist_for_each_entry_continue(c,...) S
|
hlist_for_each_entry_from(c,...) S
|
hlist_for_each_entry_safe(c,...) S
|
list_remove_head(x,c,...)
|
sizeof(<+...c...+>)
|
&c->member
|
c = E
|
*c
)

[PATCH] fs/ubifs/orphan.c: remove invalid reference to list iterator variable

[Julia Lawall]

From: Julia Lawall <Julia.Lawall@lip6.fr>

If list_for_each_entry, etc complete a traversal of the list, the iterator
variable ends up pointing to an address at an offset from the list head,
and not a meaningful structure.  Thus this value should not be used after
the end of the iterator.  Replace a field access from orphan by NULL.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@@
identifier c;
expression E;
iterator name list_for_each_entry;
statement S;
@@

list_for_each_entry(c,...) { ... when != break;
                                 when forall
                                 when strict
}
...
(
c = E
|
*c
)
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>

---
 fs/ubifs/orphan.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ubifs/orphan.c b/fs/ubifs/orphan.c
index b02734d..4b7860a 100644
--- a/fs/ubifs/orphan.c
+++ b/fs/ubifs/orphan.c
@@ -176,7 +176,7 @@ int ubifs_orphan_start_commit(struct ubifs_info *c)
 		*last = orphan;
 		last = &orphan->cnext;
 	}
-	*last = orphan->cnext;
+	*last = NULL;
 	c->cmt_orphans = c->new_orphans;
 	c->new_orphans = 0;
 	dbg_cmt("%d orphans to commit", c->cmt_orphans);

Re: [PATCH] remove invalid reference to list iterator variable

[Artem Bityutskiy]

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On Sun, 2012-07-08 at 15:19 +0200, Julia Lawall wrote:
> If list_for_each_entry, etc complete a traversal of the list, the iterator
> variable ends up pointing to an address at an offset from the list head,
> and not a meaningful structure.  Thus this value should not be used after
> the end of the iterator.

Thanks Julia - this one is very useful!

-- 
Best Regards,
Artem Bityutskiy

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