[PATCH 6.19 463/781] RDMA/iwcm: Fix workqueue list corruption by removing work_list

Greg Kroah-Hartman
2026-02-25T01:35:32Z

From: Jacob Moroni <jmoroni@google.com>

[ Upstream commit 7874eeacfa42177565c01d5198726671acf7adf2 ]

The commit e1168f0 ("RDMA/iwcm: Simplify cm_event_handler()")
changed the work submission logic to unconditionally call
queue_work() with the expectation that queue_work() would
have no effect if work was already pending. The problem is
that a free list of struct iwcm_work is used (for which
struct work_struct is embedded), so each call to queue_work()
is basically unique and therefore does indeed queue the work.

This causes a problem in the work handler which walks the work_list
until it's empty to process entries. This means that a single
run of the work handler could process item N+1 and release it
back to the free list while the actual workqueue entry is still
queued. It could then get reused (INIT_WORK...) and lead to
list corruption in the workqueue logic.

Fix this by just removing the work_list. The workqueue already
does this for us.

This fixes the following error that was observed when stress
testing with ucmatose on an Intel E830 in iWARP mode:

[ 151.465780] list_del corruption. next->prev should be ffff9f0915c69c08, but was ffff9f0a1116be08. (next=ffff9f0a15b11c08)
[ 151.466639] ------------[ cut here ]------------
[ 151.466986] kernel BUG at lib/list_debug.c:67!
[ 151.467349] Oops: invalid opcode: 0000 [#1] SMP NOPTI
[ 151.467753] CPU: 14 UID: 0 PID: 2306 Comm: kworker/u64:18 Not tainted 6.19.0-rc4+ #1 PREEMPT(voluntary)
[ 151.468466] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 151.469192] Workqueue: 0x0 (iw_cm_wq)
[ 151.469478] RIP: 0010:__list_del_entry_valid_or_report+0xf0/0x100
[ 151.469942] Code: c7 58 5f 4c b2 e8 10 50 aa ff 0f 0b 48 89 ef e8 36 57 cb ff 48 8b 55 08 48 89 e9 48 89 de 48 c7 c7 a8 5f 4c b2 e8 f0 4f aa ff <0f> 0b 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 90 90 90 90 90 90
[ 151.471323] RSP: 0000:ffffb15644e7bd68 EFLAGS: 00010046
[ 151.471712] RAX: 000000000000006d RBX: ffff9f0915c69c08 RCX: 0000000000000027
[ 151.472243] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff9f0a37d9c600
[ 151.472768] RBP: ffff9f0a15b11c08 R08: 0000000000000000 R09: c0000000ffff7fff
[ 151.473294] R10: 0000000000000001 R11: ffffb15644e7bba8 R12: ffff9f092339ee68
[ 151.473817] R13: ffff9f0900059c28 R14: ffff9f092339ee78 R15: 0000000000000000
[ 151.474344] FS: 0000000000000000(0000) GS:ffff9f0a847b5000(0000) knlGS:0000000000000000
[ 151.474934] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 151.475362] CR2: 0000559e233a9088 CR3: 000000020296b004 CR4: 0000000000770ef0
[ 151.475895] PKRU: 55555554
[ 151.476118] Call Trace:
[ 151.476331] <TASK>
[ 151.476497] move_linked_works+0x49/0xa0
[ 151.476792] __pwq_activate_work.isra.46+0x2f/0xa0
[ 151.477151] pwq_dec_nr_in_flight+0x1e0/0x2f0
[ 151.477479] process_scheduled_works+0x1c8/0x410
[ 151.477823] worker_thread+0x125/0x260
[ 151.478108] ? __pfx_worker_thread+0x10/0x10
[ 151.478430] kthread+0xfe/0x240
[ 151.478671] ? __pfx_kthread+0x10/0x10
[ 151.478955] ? __pfx_kthread+0x10/0x10
[ 151.479240] ret_from_fork+0x208/0x270
[ 151.479523] ? __pfx_kthread+0x10/0x10
[ 151.479806] ret_from_fork_asm+0x1a/0x30
[ 151.480103] </TASK>

Fixes: e1168f09b331 ("RDMA/iwcm: Simplify cm_event_handler()")
Signed-off-by: Jacob Moroni <jmoroni@google.com>
Link: https://patch.msgid.link/20260112020006.1352438-1-jmoroni@google.com
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/infiniband/core/iwcm.c | 56 +++++++++++++---------------------
drivers/infiniband/core/iwcm.h | 1 -
2 files changed, 21 insertions(+), 36 deletions(-)

diff --git a/drivers/infiniband/core/iwcm.c b/drivers/infiniband/core/iwcm.c
index 62410578dec37..eb942ab9c4055 100644
--- a/drivers/infiniband/core/iwcm.c
+++ b/drivers/infiniband/core/iwcm.c
@@ -95,7 +95,6 @@ static struct workqueue_struct *iwcm_wq;
struct iwcm_work {
struct work_struct work;
struct iwcm_id_private *cm_id;
- struct list_head list;
struct iw_cm_event event;
struct list_head free_list;
};
@@ -178,7 +177,6 @@ static int alloc_work_entries(struct iwcm_id_private *cm_id_priv, int count)
return -ENOMEM;
}
work->cm_id = cm_id_priv;
- INIT_LIST_HEAD(&work->list);
put_work(work);
}
return 0;
@@ -213,7 +211,6 @@ static void free_cm_id(struct iwcm_id_private *cm_id_priv)
static bool iwcm_deref_id(struct iwcm_id_private *cm_id_priv)
{
if (refcount_dec_and_test(&cm_id_priv->refcount)) {
- BUG_ON(!list_empty(&cm_id_priv->work_list));
free_cm_id(cm_id_priv);
return true;
}
@@ -260,7 +257,6 @@ struct iw_cm_id *iw_create_cm_id(struct ib_device *device,
refcount_set(&cm_id_priv->refcount, 1);
init_waitqueue_head(&cm_id_priv->connect_wait);
init_completion(&cm_id_priv->destroy_comp);
- INIT_LIST_HEAD(&cm_id_priv->work_list);
INIT_LIST_HEAD(&cm_id_priv->work_free_list);

return &cm_id_priv->id;
@@ -1007,13 +1003,13 @@ static int process_event(struct iwcm_id_private *cm_id_priv,
}

/*
- * Process events on the work_list for the cm_id. If the callback
- * function requests that the cm_id be deleted, a flag is set in the
- * cm_id flags to indicate that when the last reference is
- * removed, the cm_id is to be destroyed. This is necessary to
- * distinguish between an object that will be destroyed by the app
- * thread asleep on the destroy_comp list vs. an object destroyed
- * here synchronously when the last reference is removed.
+ * Process events for the cm_id. If the callback function requests
+ * that the cm_id be deleted, a flag is set in the cm_id flags to
+ * indicate that when the last reference is removed, the cm_id is
+ * to be destroyed. This is necessary to distinguish between an
+ * object that will be destroyed by the app thread asleep on the
+ * destroy_comp list vs. an object destroyed here synchronously
+ * when the last reference is removed.
*/
static void cm_work_handler(struct work_struct *_work)
{
@@ -1024,35 +1020,26 @@ static void cm_work_handler(struct work_struct *_work)
int ret = 0;

spin_lock_irqsave(&cm_id_priv->lock, flags);
- while (!list_empty(&cm_id_priv->work_list)) {
- work = list_first_entry(&cm_id_priv->work_list,
- struct iwcm_work, list);
- list_del_init(&work->list);
- levent = work->event;
- put_work(work);
- spin_unlock_irqrestore(&cm_id_priv->lock, flags);
-
- if (!test_bit(IWCM_F_DROP_EVENTS, &cm_id_priv->flags)) {
- ret = process_event(cm_id_priv, &levent);
- 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))
- return;
- spin_lock_irqsave(&cm_id_priv->lock, flags);
- }
+ levent = work->event;
+ put_work(work);
spin_unlock_irqrestore(&cm_id_priv->lock, flags);
+
+ if (!test_bit(IWCM_F_DROP_EVENTS, &cm_id_priv->flags)) {
+ ret = process_event(cm_id_priv, &levent);
+ 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))
+ return;
}

/*
* This function is called on interrupt context. Schedule events on
* the iwcm_wq thread to allow callback functions to downcall into
- * the CM and/or block. Events are queued to a per-CM_ID
- * work_list. If this is the first event on the work_list, the work
- * element is also queued on the iwcm_wq thread.
+ * the CM and/or block.
*
* Each event holds a reference on the cm_id. Until the last posted
* event has been delivered and processed, the cm_id cannot be
@@ -1094,7 +1081,6 @@ static int cm_event_handler(struct iw_cm_id *cm_id,
}

refcount_inc(&cm_id_priv->refcount);
- list_add_tail(&work->list, &cm_id_priv->work_list);
queue_work(iwcm_wq, &work->work);
out:
spin_unlock_irqrestore(&cm_id_priv->lock, flags);
diff --git a/drivers/infiniband/core/iwcm.h b/drivers/infiniband/core/iwcm.h
index bf74639be1287..b56fb12edece4 100644
--- a/drivers/infiniband/core/iwcm.h
+++ b/drivers/infiniband/core/iwcm.h
@@ -50,7 +50,6 @@ struct iwcm_id_private {
struct ib_qp *qp;
struct completion destroy_comp;
wait_queue_head_t connect_wait;
- struct list_head work_list;
spinlock_t lock;
refcount_t refcount;
struct list_head work_free_list;
--
2.51.0