[PATCH v2] dmaengine: idxd: fix use-after-free in idxd_free() and idxd_alloc() error paths

["Bogdan Codres (Wind River)" <bogdan.codres@windriver.com>]

From: Bogdan Codres <bogdan.codres@windriver.com>

[   18.628791] idxd 0000:00:01.0: Device is HALTED!
[   18.631447] idxd 0000:00:01.0: Intel(R) IDXD DMA Engine init failed
[   18.631450] ------------[ cut here ]------------
[   18.631451] ida_free called for id=0 which is not allocated.
[   18.631462] WARNING: CPU: 0 PID: 11 at lib/idr.c:525 ida_free+0xd3/0x130
[   18.631474] CPU: 0 UID: 0 PID: 11 Comm: kworker/0:1 Not tainted 6.12.0-1-rt-amd64 #1
[   18.631477] Hardware name: Dell Inc. PowerEdge XR8720t/0J91KV, BIOS 1.1.3 02/03/2026
[   18.631478] Workqueue: events work_for_cpu_fn
[   18.631480] RIP: 0010:ida_free+0xd3/0x130
[   18.631492] Call Trace:
[   18.631494]  <TASK>
[   18.631495]  idxd_pci_probe+0x1b0/0x1860 [idxd]
[   18.631506]  local_pci_probe+0x43/0xa0
[   18.631508]  work_for_cpu_fn+0x13/0x20
[   18.631510]  process_one_work+0x179/0x390
[   18.631512]  worker_thread+0x237/0x340
[   18.631517]  kthread+0xc6/0x100
[   18.631520]  ret_from_fork+0x2d/0x50
[   18.631524]  ret_from_fork_asm+0x1a/0x30
[   18.631526]  </TASK>

idxd_free() calls put_device(idxd_confdev(idxd)) which drops the last
reference and synchronously invokes idxd_conf_device_release(). That
release callback already frees idxd->opcap_bmap, idxd->id (via
ida_free), and the idxd structure itself. The subsequent bitmap_free(),
ida_free(), and kfree() in idxd_free() therefore operate on freed
memory - a double-free that corrupts the slab allocator.

The same pattern exists in idxd_alloc() at the err_name label where
put_device() is followed by bitmap_free() fall-through.

Fix both by letting put_device() handle all resource cleanup via the
release callback, removing the duplicate frees.

Fixes: 90022b3a6981 ("dmaengine: idxd: fix memory leak in error handling path of idxd_pci_probe")
Fixes: 46a5cca76c76 ("dmaengine: idxd: fix memory leak in error handling path of idxd_alloc")
Cc: stable@vger.kernel.org
Signed-off-by: Bogdan Codres <bogdan.codres@windriver.com>
---
 drivers/dma/idxd/init.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
index 18997f80bdc9..ce4d58740c88 100644
--- a/drivers/dma/idxd/init.c
+++ b/drivers/dma/idxd/init.c
@@ -585,15 +585,18 @@ static void idxd_read_caps(struct idxd_device *idxd)
 		idxd->hw.iaa_cap.bits = ioread64(idxd->reg_base + IDXD_IAACAP_OFFSET);
 }
 
+/*
+ * Release an idxd device that was allocated (device_initialize() was called)
+ * but never successfully registered. put_device() drops the last reference and
+ * triggers idxd_conf_device_release() which frees all resources including the
+ * ida, opcap_bmap, and the idxd structure itself.
+ */
 static void idxd_free(struct idxd_device *idxd)
 {
 	if (!idxd)
 		return;
 
 	put_device(idxd_confdev(idxd));
-	bitmap_free(idxd->opcap_bmap);
-	ida_free(&idxd_ida, idxd->id);
-	kfree(idxd);
 }
 
 static struct idxd_device *idxd_alloc(struct pci_dev *pdev, struct idxd_driver_data *data)
@@ -633,8 +636,12 @@ static struct idxd_device *idxd_alloc(struct pci_dev *pdev, struct idxd_driver_d
 	return idxd;
 
 err_name:
+	/* device_initialize() was called, so put_device() will trigger
+	 * idxd_conf_device_release() which frees ida, opcap_bmap, and idxd.
+	 * Do not fall through to err_opcap/err_ida.
+	 */
 	put_device(conf_dev);
-	bitmap_free(idxd->opcap_bmap);
+	return NULL;
 err_opcap:
 	ida_free(&idxd_ida, idxd->id);
 err_ida:
-- 
2.51.0