diff options
| author | Nikolay Kuratov <kniv@yandex-team.ru> | 2025-08-05 16:09:17 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-09-04 16:31:44 +0300 |
| commit | cbc00a76a5ff91098577d8aac321b00b6d139b75 (patch) | |
| tree | 6c104e7cde3cd79476040b2406c78cc2422b2e67 /drivers/vhost/net.c | |
| parent | f5da8116cd52e0cdd6eaea949b49c9dca8d8233d (diff) | |
| download | linux-cbc00a76a5ff91098577d8aac321b00b6d139b75.tar.xz | |
vhost/net: Protect ubufs with rcu read lock in vhost_net_ubuf_put()
commit dd54bcf86c91a4455b1f95cbc8e9ac91205f3193 upstream.
When operating on struct vhost_net_ubuf_ref, the following execution
sequence is theoretically possible:
CPU0 is finalizing DMA operation CPU1 is doing VHOST_NET_SET_BACKEND
// ubufs->refcount == 2
vhost_net_ubuf_put() vhost_net_ubuf_put_wait_and_free(oldubufs)
vhost_net_ubuf_put_and_wait()
vhost_net_ubuf_put()
int r = atomic_sub_return(1, &ubufs->refcount);
// r = 1
int r = atomic_sub_return(1, &ubufs->refcount);
// r = 0
wait_event(ubufs->wait, !atomic_read(&ubufs->refcount));
// no wait occurs here because condition is already true
kfree(ubufs);
if (unlikely(!r))
wake_up(&ubufs->wait); // use-after-free
This leads to use-after-free on ubufs access. This happens because CPU1
skips waiting for wake_up() when refcount is already zero.
To prevent that use a read-side RCU critical section in vhost_net_ubuf_put(),
as suggested by Hillf Danton. For this lock to take effect, free ubufs with
kfree_rcu().
Cc: stable@vger.kernel.org
Fixes: 0ad8b480d6ee9 ("vhost: fix ref cnt checking deadlock")
Reported-by: Andrey Ryabinin <arbn@yandex-team.com>
Suggested-by: Hillf Danton <hdanton@sina.com>
Signed-off-by: Nikolay Kuratov <kniv@yandex-team.ru>
Message-Id: <20250805130917.727332-1-kniv@yandex-team.ru>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/vhost/net.c')
| -rw-r--r-- | drivers/vhost/net.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index f16279351db5..aff4ec783562 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -96,6 +96,7 @@ struct vhost_net_ubuf_ref { atomic_t refcount; wait_queue_head_t wait; struct vhost_virtqueue *vq; + struct rcu_head rcu; }; #define VHOST_NET_BATCH 64 @@ -247,9 +248,13 @@ vhost_net_ubuf_alloc(struct vhost_virtqueue *vq, bool zcopy) static int vhost_net_ubuf_put(struct vhost_net_ubuf_ref *ubufs) { - int r = atomic_sub_return(1, &ubufs->refcount); + int r; + + rcu_read_lock(); + r = atomic_sub_return(1, &ubufs->refcount); if (unlikely(!r)) wake_up(&ubufs->wait); + rcu_read_unlock(); return r; } @@ -262,7 +267,7 @@ static void vhost_net_ubuf_put_and_wait(struct vhost_net_ubuf_ref *ubufs) static void vhost_net_ubuf_put_wait_and_free(struct vhost_net_ubuf_ref *ubufs) { vhost_net_ubuf_put_and_wait(ubufs); - kfree(ubufs); + kfree_rcu(ubufs, rcu); } static void vhost_net_clear_ubuf_info(struct vhost_net *n) |