The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x 6883b680e703c6b2efddb4e7a8d891ce1803d06b # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025062004-henchman-staging-7b05@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 6883b680e703c6b2efddb4e7a8d891ce1803d06b Mon Sep 17 00:00:00 2001 From: Shin'ichiro Kawasaki shinichiro.kawasaki@wdc.com Date: Sat, 10 May 2025 19:10:36 +0900 Subject: [PATCH] RDMA/iwcm: Fix use-after-free of work objects after cm_id destruction

The commit 59c68ac31e15 ("iw_cm: free cm_id resources on the last deref") simplified cm_id resource management by freeing cm_id once all references to the cm_id were removed. The references are removed either upon completion of iw_cm event handlers or when the application destroys the cm_id. This commit introduced the use-after-free condition where cm_id_private object could still be in use by event handler works during the destruction of cm_id. The commit aee2424246f9 ("RDMA/iwcm: Fix a use-after-free related to destroying CM IDs") addressed this use-after- free by flushing all pending works at the cm_id destruction.

However, still another use-after-free possibility remained. It happens with the work objects allocated for each cm_id_priv within alloc_work_entries() during cm_id creation, and subsequently freed in dealloc_work_entries() once all references to the cm_id are removed. If the cm_id's last reference is decremented in the event handler work, the work object for the work itself gets removed, and causes the use- after-free BUG below:

BUG: KASAN: slab-use-after-free in __pwq_activate_work+0x1ff/0x250 Read of size 8 at addr ffff88811f9cf800 by task kworker/u16:1/147091

CPU: 2 UID: 0 PID: 147091 Comm: kworker/u16:1 Not tainted 6.15.0-rc2+ #27 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014 Workqueue: 0x0 (iw_cm_wq) Call Trace: <TASK> dump_stack_lvl+0x6a/0x90 print_report+0x174/0x554 ? __virt_addr_valid+0x208/0x430 ? __pwq_activate_work+0x1ff/0x250 kasan_report+0xae/0x170 ? __pwq_activate_work+0x1ff/0x250 __pwq_activate_work+0x1ff/0x250 pwq_dec_nr_in_flight+0x8c5/0xfb0 process_one_work+0xc11/0x1460 ? __pfx_process_one_work+0x10/0x10 ? assign_work+0x16c/0x240 worker_thread+0x5ef/0xfd0 ? __pfx_worker_thread+0x10/0x10 kthread+0x3b0/0x770 ? __pfx_kthread+0x10/0x10 ? rcu_is_watching+0x11/0xb0 ? _raw_spin_unlock_irq+0x24/0x50 ? rcu_is_watching+0x11/0xb0 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x30/0x70 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK>

Allocated by task 147416: kasan_save_stack+0x2c/0x50 kasan_save_track+0x10/0x30 __kasan_kmalloc+0xa6/0xb0 alloc_work_entries+0xa9/0x260 [iw_cm] iw_cm_connect+0x23/0x4a0 [iw_cm] rdma_connect_locked+0xbfd/0x1920 [rdma_cm] nvme_rdma_cm_handler+0x8e5/0x1b60 [nvme_rdma] cma_cm_event_handler+0xae/0x320 [rdma_cm] cma_work_handler+0x106/0x1b0 [rdma_cm] process_one_work+0x84f/0x1460 worker_thread+0x5ef/0xfd0 kthread+0x3b0/0x770 ret_from_fork+0x30/0x70 ret_from_fork_asm+0x1a/0x30

Freed by task 147091: kasan_save_stack+0x2c/0x50 kasan_save_track+0x10/0x30 kasan_save_free_info+0x37/0x60 __kasan_slab_free+0x4b/0x70 kfree+0x13a/0x4b0 dealloc_work_entries+0x125/0x1f0 [iw_cm] iwcm_deref_id+0x6f/0xa0 [iw_cm] cm_work_handler+0x136/0x1ba0 [iw_cm] process_one_work+0x84f/0x1460 worker_thread+0x5ef/0xfd0 kthread+0x3b0/0x770 ret_from_fork+0x30/0x70 ret_from_fork_asm+0x1a/0x30

Last potentially related work creation: kasan_save_stack+0x2c/0x50 kasan_record_aux_stack+0xa3/0xb0 __queue_work+0x2ff/0x1390 queue_work_on+0x67/0xc0 cm_event_handler+0x46a/0x820 [iw_cm] siw_cm_upcall+0x330/0x650 [siw] siw_cm_work_handler+0x6b9/0x2b20 [siw] process_one_work+0x84f/0x1460 worker_thread+0x5ef/0xfd0 kthread+0x3b0/0x770 ret_from_fork+0x30/0x70 ret_from_fork_asm+0x1a/0x30

This BUG is reproducible by repeating the blktests test case nvme/061 for the rdma transport and the siw driver.

To avoid the use-after-free of cm_id_private work objects, ensure that the last reference to the cm_id is decremented not in the event handler works, but in the cm_id destruction context. For that purpose, move iwcm_deref_id() call from destroy_cm_id() to the callers of destroy_cm_id(). In iw_destroy_cm_id(), call iwcm_deref_id() after flushing the pending works.

During the fix work, I noticed that iw_destroy_cm_id() is called from cm_work_handler() and process_event() context. However, the comment of iw_destroy_cm_id() notes that the function "cannot be called by the event thread". Drop the false comment.

Closes: https://lore.kernel.org/linux-rdma/r5676e754sv35aq7cdsqrlnvyhiq5zktteaurl7vm... Fixes: 59c68ac31e15 ("iw_cm: free cm_id resources on the last deref") Cc: stable@vger.kernel.org Signed-off-by: Shin'ichiro Kawasaki shinichiro.kawasaki@wdc.com Link: https://patch.msgid.link/20250510101036.1756439-1-shinichiro.kawasaki@wdc.co... Reviewed-by: Zhu Yanjun yanjun.zhu@linux.dev Signed-off-by: Leon Romanovsky leon@kernel.org

diff --git a/drivers/infiniband/core/iwcm.c b/drivers/infiniband/core/iwcm.c index f4486cbd8f45..62410578dec3 100644 --- a/drivers/infiniband/core/iwcm.c +++ b/drivers/infiniband/core/iwcm.c @@ -368,12 +368,9 @@ EXPORT_SYMBOL(iw_cm_disconnect); /* * CM_ID <-- DESTROYING * - * Clean up all resources associated with the connection and release - * the initial reference taken by iw_create_cm_id. - * - * Returns true if and only if the last cm_id_priv reference has been dropped. + * Clean up all resources associated with the connection. */ -static bool destroy_cm_id(struct iw_cm_id *cm_id) +static void destroy_cm_id(struct iw_cm_id *cm_id) { struct iwcm_id_private *cm_id_priv; struct ib_qp *qp; @@ -442,20 +439,22 @@ static bool destroy_cm_id(struct iw_cm_id *cm_id) iwpm_remove_mapinfo(&cm_id->local_addr, &cm_id->m_local_addr); iwpm_remove_mapping(&cm_id->local_addr, RDMA_NL_IWCM); } - - return iwcm_deref_id(cm_id_priv); }

/* - * This function is only called by the application thread and cannot - * be called by the event thread. The function will wait for all - * references to be released on the cm_id and then kfree the cm_id - * object. + * Destroy cm_id. If the cm_id still has other references, wait for all + * references to be released on the cm_id and then release the initial + * reference taken by iw_create_cm_id. */ void iw_destroy_cm_id(struct iw_cm_id *cm_id) { - if (!destroy_cm_id(cm_id)) + struct iwcm_id_private *cm_id_priv; + + cm_id_priv = container_of(cm_id, struct iwcm_id_private, id); + destroy_cm_id(cm_id); + if (refcount_read(&cm_id_priv->refcount) > 1) flush_workqueue(iwcm_wq); + iwcm_deref_id(cm_id_priv); } EXPORT_SYMBOL(iw_destroy_cm_id);

@@ -1035,8 +1034,10 @@ static void cm_work_handler(struct work_struct *_work)

if (!test_bit(IWCM_F_DROP_EVENTS, &cm_id_priv->flags)) { ret = process_event(cm_id_priv, &levent); - if (ret) - WARN_ON_ONCE(destroy_cm_id(&cm_id_priv->id)); + if (ret) { + destroy_cm_id(&cm_id_priv->id); + WARN_ON_ONCE(iwcm_deref_id(cm_id_priv)); + } } else pr_debug("dropping event %d\n", levent.event); if (iwcm_deref_id(cm_id_priv))