03/05/2023 06:44, Honnappa Nagarahalli пишет:
<snip>
After the memzone is freed, it is not removed from the 'rte_ring_tailq'.
If rte_ring_lookup is called at this time, it will cause a
use-after-free problem. This change prevents that from happening.
Fixes: 4e32101f9b01 ("ring: support freeing")
Cc: sta...@dpdk.org
Suggested-by: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>
Signed-off-by: Yunjian Wang <wangyunj...@huawei.com>
---
v2: update code suggested by Honnappa Nagarahalli
---
lib/ring/rte_ring.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/lib/ring/rte_ring.c b/lib/ring/rte_ring.c index
8ed455043d..2755323b8a 100644
--- a/lib/ring/rte_ring.c
+++ b/lib/ring/rte_ring.c
@@ -333,11 +333,6 @@ rte_ring_free(struct rte_ring *r)
return;
}
- if (rte_memzone_free(r->memzone) != 0) {
- RTE_LOG(ERR, RING, "Cannot free memory\n");
- return;
- }
-
ring_list = RTE_TAILQ_CAST(rte_ring_tailq.head, rte_ring_list);
rte_mcfg_tailq_write_lock();
@@ -354,6 +349,9 @@ rte_ring_free(struct rte_ring *r)
TAILQ_REMOVE(ring_list, te, next);
+ if (rte_memzone_free(r->memzone) != 0)
+ RTE_LOG(ERR, RING, "Cannot free memory\n");
+
I nit: I think it is a bit better to first release the lock and then
free the memzone.
I think both of our suggestions are contradictory. Any reason why you want
to free outside the locked region?
Don't know what you mean by 'both suggestions' here.
I wrote 'both of our suggestions'. Essentially, in v1, freeing the memzone was
outside of the lock. I suggested to move it inside and you are suggesting to
move it inside.
Ah ok, I missed v1 and your comments for it.
As I said before, I don't think that we need to hold qlock here
while calling mmezone_free().
Though I don't see any harm with it either.
I'd personally would move memzone_free() after releasing qlock,
but if you guys prefer to keep it as it is - I wouldn't insist.
I think I gave only one - move memzone_free() after tailq_write_unlock().
To be more precise:
1) rte_mcfg_tailq_write_lock();
...
2) TAILQ_REMOVE(...);
3) rte_mcfg_tailq_write_unlock();
4) rte_memzone_free(r->memzone);
As I remember, memzones are protected by their own lock (mlock), so we
don't need to hold qlock to free a memzone, after ring was already removed
from the ring_list.
I thought, since it belongs to the ring being freed, it makes sense to free it
while holding the lock to avoid any race conditions (though, I have not
checked what those are).
As I understand, it is ok with current design to grab mlock while holding qlock.
So, there is nothing wrong with current patch, I just think that in that case
it is
excessive, and can be safely avoided.
Apart from that, LGTM.
Acked-by: Konstantin Ananyev <konstantin.v.anan...@yandex.ru>
rte_mcfg_tailq_write_unlock();
rte_free(te);
--
2.33.0
