RDMA/iwcm: Fix use-after-free of work objects after cm_id destruction

In the Linux kernel, the following vulnerability has been resolved:

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, mo

---truncated---