2022-04-01 03:00:13

by Jakob Koschel

Subject: [PATCH] crypto: cavium/nitrox - remove check of list iterator against head past the loop body

When list_for_each_entry() completes the iteration over the whole list
without breaking the loop, the iterator value will be a bogus pointer
computed based on the head element.

While it is safe to use the pointer to determine if it was computed
based on the head element, either with list_entry_is_head() or
&pos->member == head, using the iterator variable after the loop should
be avoided.

In preparation to limit the scope of a list iterator to the list
traversal loop, use a dedicated pointer to point to the found element [1].

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
Signed-off-by: Jakob Koschel <[email protected]>
---
drivers/crypto/cavium/nitrox/nitrox_main.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/crypto/cavium/nitrox/nitrox_main.c b/drivers/crypto/cavium/nitrox/nitrox_main.c
index 6c61817996a3..432a61aca0c5 100644
--- a/drivers/crypto/cavium/nitrox/nitrox_main.c
+++ b/drivers/crypto/cavium/nitrox/nitrox_main.c
@@ -269,15 +269,17 @@ static void nitrox_remove_from_devlist(struct nitrox_device *ndev)

struct nitrox_device *nitrox_get_first_device(void)
{
- struct nitrox_device *ndev;
+ struct nitrox_device *ndev = NULL, *iter;

mutex_lock(&devlist_lock);
- list_for_each_entry(ndev, &ndevlist, list) {
- if (nitrox_ready(ndev))
+ list_for_each_entry(iter, &ndevlist, list) {
+ if (nitrox_ready(iter)) {
+ ndev = iter;
break;
+ }
}
mutex_unlock(&devlist_lock);
- if (&ndev->list == &ndevlist)
+ if (!ndev)
return NULL;

refcount_inc(&ndev->refcnt);

base-commit: f82da161ea75dc4db21b2499e4b1facd36dab275
--
2.25.1

2022-04-08 08:51:49

by Herbert Xu

Subject: Re: [PATCH] crypto: cavium/nitrox - remove check of list iterator against head past the loop body

On Thu, Mar 31, 2022 at 11:59:10PM +0200, Jakob Koschel wrote:
> When list_for_each_entry() completes the iteration over the whole list
> without breaking the loop, the iterator value will be a bogus pointer
> computed based on the head element.
>
> While it is safe to use the pointer to determine if it was computed
> based on the head element, either with list_entry_is_head() or
> &pos->member == head, using the iterator variable after the loop should
> be avoided.
>
> In preparation to limit the scope of a list iterator to the list
> traversal loop, use a dedicated pointer to point to the found element [1].
>
> Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
> Signed-off-by: Jakob Koschel <[email protected]>
> ---
> drivers/crypto/cavium/nitrox/nitrox_main.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)

Patch applied. Thanks.
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt