On Wed, Nov 18, 2020 at 03:10:21AM -0800, syzbot wrote: > HEAD commit: 20529233 Add linux-next specific files for 20201118 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=13093cf2500000 > kernel config: https://syzkaller.appspot.com/x/.config?x=2c4fb58b6526b3c1 > dashboard link: https://syzkaller.appspot.com/bug?extid=1bc48bf7f78253f664a9 > compiler: gcc (GCC) 10.1.0-syz 20200507 > > Unfortunately, I don't have any reproducer for this issue yet. Oh? Is this because the error injection is too random? > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+1bc48bf7f78253f664a9@xxxxxxxxxxxxxxxxxxxxxxxxx > > iwpm_register_pid: Unable to send a nlmsg (client = 2) > infiniband syz1: RDMA CMA: cma_listen_on_dev, error -98 > ============================================ > WARNING: possible recursive locking detected > 5.10.0-rc4-next-20201118-syzkaller #0 Not tainted > syz-executor.5/12844 is trying to acquire lock: > ffffffff8c684748 (lock#6){+.+.}-{3:3}, at: cma_release_dev drivers/infiniband/core/cma.c:476 [inline] > ffffffff8c684748 (lock#6){+.+.}-{3:3}, at: _destroy_id+0x299/0xa00 drivers/infiniband/core/cma.c:1852 > > but task is already holding lock: > ffffffff8c684748 (lock#6){+.+.}-{3:3}, at: cma_add_one+0x55c/0xce0 drivers/infiniband/core/cma.c:4902 Leon, this is caused by commit c80a0c52d85c49a910d0dc0e342e8d8898677dc0 Author: Leon Romanovsky <leon@xxxxxxxxxx> Date: Wed Nov 4 16:40:07 2020 +0200 RDMA/cma: Add missing error handling of listen_id Don't silently continue if rdma_listen() fails but destroy previously created CM_ID and return an error to the caller. rdma_destroy_id() can't be called while holding the global lock This is quite hard to fix. I came up with this ugly thing: >From 8e6568f99fbe4bf734cc4e5dcda987e4ae118bdd Mon Sep 17 00:00:00 2001 From: Jason Gunthorpe <jgg@xxxxxxxxxx> Date: Wed, 18 Nov 2020 09:33:23 -0400 Subject: [PATCH] RDMA/cma: Fix deadlock on &lock in rdma_cma_listen_on_all() error unwind rdma_detroy_id() cannot be called under &lock - we must instead keep the error'd ID around until &lock can be released, then destory it. This is complicated by the usual way listen IDs are destroyed through cma_process_remove() which can run at any time and will asynchronously destroy the same ID. Remove the ID from visiblity of cma_process_remove() before going down the destroy path outside the locking. Fixes: c80a0c52d85c ("RDMA/cma: Add missing error handling of listen_id") Reported-by: syzbot+1bc48bf7f78253f664a9@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx> --- drivers/infiniband/core/cma.c | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-) diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c index 4585f654f88369..c06c87a4dc5e7d 100644 --- a/drivers/infiniband/core/cma.c +++ b/drivers/infiniband/core/cma.c @@ -2496,7 +2496,8 @@ static int cma_listen_handler(struct rdma_cm_id *id, } static int cma_listen_on_dev(struct rdma_id_private *id_priv, - struct cma_device *cma_dev) + struct cma_device *cma_dev, + struct rdma_id_private **to_destroy) { struct rdma_id_private *dev_id_priv; struct net *net = id_priv->id.route.addr.dev_addr.net; @@ -2504,6 +2505,7 @@ static int cma_listen_on_dev(struct rdma_id_private *id_priv, lockdep_assert_held(&lock); + *to_destroy = NULL; if (cma_family(id_priv) == AF_IB && !rdma_cap_ib_cm(cma_dev->device, 1)) return 0; @@ -2518,7 +2520,6 @@ static int cma_listen_on_dev(struct rdma_id_private *id_priv, rdma_addr_size(cma_src_addr(id_priv))); _cma_attach_to_dev(dev_id_priv, cma_dev); - list_add_tail(&dev_id_priv->listen_list, &id_priv->listen_list); cma_id_get(id_priv); dev_id_priv->internal_id = 1; dev_id_priv->afonly = id_priv->afonly; @@ -2528,25 +2529,31 @@ static int cma_listen_on_dev(struct rdma_id_private *id_priv, ret = rdma_listen(&dev_id_priv->id, id_priv->backlog); if (ret) goto err_listen; + list_add_tail(&dev_id_priv->listen_list, &id_priv->listen_list); return 0; err_listen: - list_del(&id_priv->listen_list); + /* Caller must destroy this after releasing lock */ + *to_destroy = dev_id_priv; dev_warn(&cma_dev->device->dev, "RDMA CMA: %s, error %d\n", __func__, ret); - rdma_destroy_id(&dev_id_priv->id); return ret; } static int cma_listen_on_all(struct rdma_id_private *id_priv) { + struct rdma_id_private *to_destroy; struct cma_device *cma_dev; int ret; mutex_lock(&lock); list_add_tail(&id_priv->list, &listen_any_list); list_for_each_entry(cma_dev, &dev_list, list) { - ret = cma_listen_on_dev(id_priv, cma_dev); - if (ret) + ret = cma_listen_on_dev(id_priv, cma_dev, &to_destroy); + if (ret) { + /* Prevent racing with cma_process_remove() */ + if (to_destroy) + list_del_init(&to_destroy->list); goto err_listen; + } } mutex_unlock(&lock); return 0; @@ -2554,6 +2561,8 @@ static int cma_listen_on_all(struct rdma_id_private *id_priv) err_listen: list_del(&id_priv->list); mutex_unlock(&lock); + if (to_destroy) + rdma_destroy_id(&to_destroy->id); return ret; } @@ -4855,6 +4864,7 @@ static void cma_process_remove(struct cma_device *cma_dev) static int cma_add_one(struct ib_device *device) { + struct rdma_id_private *to_destroy; struct cma_device *cma_dev; struct rdma_id_private *id_priv; unsigned int i; @@ -4902,7 +4912,7 @@ static int cma_add_one(struct ib_device *device) mutex_lock(&lock); list_add_tail(&cma_dev->list, &dev_list); list_for_each_entry(id_priv, &listen_any_list, list) { - ret = cma_listen_on_dev(id_priv, cma_dev); + ret = cma_listen_on_dev(id_priv, cma_dev, &to_destroy); if (ret) goto free_listen; } @@ -4915,6 +4925,7 @@ static int cma_add_one(struct ib_device *device) list_del(&cma_dev->list); mutex_unlock(&lock); + /* cma_process_remove() will delete to_destroy */ cma_process_remove(cma_dev); kfree(cma_dev->default_roce_tos); free_gid_type: -- 2.29.2
