[PATCH AUTOSEL 6.6 011/139] net/xen-netback: prevent UAF in xenvif_flush_hash()

Sasha Levin
2024-09-25T12:12:05Z

From: Jeongjun Park <aha310510@gmail.com>

[ Upstream commit 0fa5e94a1811d68fbffa0725efe6d4ca62c03d12 ]

During the list_for_each_entry_rcu iteration call of xenvif_flush_hash,
kfree_rcu does not exist inside the rcu read critical section, so if
kfree_rcu is called when the rcu grace period ends during the iteration,
UAF occurs when accessing head->next after the entry becomes free.

Therefore, to solve this, you need to change it to list_for_each_entry_safe.

Signed-off-by: Jeongjun Park <aha310510@gmail.com>
Link: https://patch.msgid.link/20240822181109.2577354-1-aha310510@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/xen-netback/hash.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/xen-netback/hash.c b/drivers/net/xen-netback/hash.c
index ff96f22648efd..45ddce35f6d2c 100644
--- a/drivers/net/xen-netback/hash.c
+++ b/drivers/net/xen-netback/hash.c
@@ -95,7 +95,7 @@ static u32 xenvif_new_hash(struct xenvif *vif, const u8 *data,

static void xenvif_flush_hash(struct xenvif *vif)
{
- struct xenvif_hash_cache_entry *entry;
+ struct xenvif_hash_cache_entry *entry, *n;
unsigned long flags;

if (xenvif_hash_cache_size == 0)
@@ -103,8 +103,7 @@ static void xenvif_flush_hash(struct xenvif *vif)

spin_lock_irqsave(&vif->hash.cache.lock, flags);

- list_for_each_entry_rcu(entry, &vif->hash.cache.list, link,
- lockdep_is_held(&vif->hash.cache.lock)) {
+ list_for_each_entry_safe(entry, n, &vif->hash.cache.list, link) {
list_del_rcu(&entry->link);
vif->hash.cache.count--;
kfree_rcu(entry, rcu);
--
2.43.0