* Re: [syzbot] KASAN: slab-use-after-free Read in vhci_send_cmd_submit
2026-08-20 14:58 [syzbot] KASAN: slab-use-after-free Read in vhci_send_cmd_submit syzbot
@ 2026-08-21 3:13 ` Edward Adam Davis
2026-08-21 3:29 ` syzbot
2026-08-21 4:55 ` Hillf Danton
2026-08-21 13:08 ` [PATCH] usbip: prevent the use of unavailable urb and hcpriv in tx Edward Adam Davis
2 siblings, 1 reply; 6+ messages in thread
From: Edward Adam Davis @ 2026-08-21 3:13 UTC (permalink / raw)
To: syzbot+ecbb1750082f7528b507; +Cc: linux-kernel, syzkaller-bugs
#syz test
diff --git a/drivers/usb/usbip/vhci_tx.c b/drivers/usb/usbip/vhci_tx.c
index 32e6fabccf72..c3aacbb6939f 100644
--- a/drivers/usb/usbip/vhci_tx.c
+++ b/drivers/usb/usbip/vhci_tx.c
@@ -13,7 +13,12 @@
static void setup_cmd_submit_pdu(struct usbip_header *pdup, struct urb *urb)
{
struct vhci_priv *priv = ((struct vhci_priv *)urb->hcpriv);
- struct vhci_device *vdev = priv->vdev;
+ struct vhci_device *vdev;
+
+ if (!priv)
+ return;
+
+ vdev = priv->vdev;
usbip_dbg_vhci_tx("URB, local devnum %u, remote devid %u\n",
usb_pipedevice(urb->pipe), vdev->devid);
@@ -68,7 +73,9 @@ static int vhci_send_cmd_submit(struct vhci_device *vdev)
int ret;
struct urb *urb = priv->urb;
struct usbip_header pdu_header;
+ unsigned long flags;
+ usb_get_urb(urb);
txsize = 0;
memset(&pdu_header, 0, sizeof(pdu_header));
memset(&msg, 0, sizeof(msg));
@@ -85,6 +92,7 @@ static int vhci_send_cmd_submit(struct vhci_device *vdev)
iov = kzalloc_objs(*iov, iovnum);
if (!iov) {
usbip_event_add(&vdev->ud, SDEV_EVENT_ERROR_MALLOC);
+ usb_put_urb(urb);
return -ENOMEM;
}
@@ -92,7 +100,14 @@ static int vhci_send_cmd_submit(struct vhci_device *vdev)
urb->transfer_flags |= URB_DMA_MAP_SG;
/* 1. setup usbip_header */
+ spin_lock_irqsave(&vdev->priv_lock, flags);
+ if (!urb->hcpriv) {
+ usb_put_urb(urb);
+ spin_unlock_irqrestore(&vdev->priv_lock, flags);
+ return -EIO;
+ }
setup_cmd_submit_pdu(&pdu_header, urb);
+ spin_unlock_irqrestore(&vdev->priv_lock, flags);
usbip_header_correct_endian(&pdu_header, 1);
iovnum = 0;
@@ -127,6 +142,7 @@ static int vhci_send_cmd_submit(struct vhci_device *vdev)
if (!iso_buffer) {
usbip_event_add(&vdev->ud,
SDEV_EVENT_ERROR_MALLOC);
+ usb_put_urb(urb);
goto err_iso_buffer;
}
@@ -143,6 +159,7 @@ static int vhci_send_cmd_submit(struct vhci_device *vdev)
txsize);
usbip_event_add(&vdev->ud, VDEV_EVENT_ERROR_TCP);
err = -EPIPE;
+ usb_put_urb(urb);
goto err_tx;
}
@@ -154,6 +171,7 @@ static int vhci_send_cmd_submit(struct vhci_device *vdev)
usbip_dbg_vhci_tx("send txdata\n");
total_size += txsize;
+ usb_put_urb(urb);
}
return total_size;
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [syzbot] KASAN: slab-use-after-free Read in vhci_send_cmd_submit
2026-08-20 14:58 [syzbot] KASAN: slab-use-after-free Read in vhci_send_cmd_submit syzbot
2026-08-21 3:13 ` Edward Adam Davis
@ 2026-08-21 4:55 ` Hillf Danton
2026-08-21 5:11 ` syzbot
2026-08-21 13:08 ` [PATCH] usbip: prevent the use of unavailable urb and hcpriv in tx Edward Adam Davis
2 siblings, 1 reply; 6+ messages in thread
From: Hillf Danton @ 2026-08-21 4:55 UTC (permalink / raw)
To: syzbot; +Cc: linux-kernel, syzkaller-bugs
> Date: Thu, 20 Aug 2026 07:58:25 -0700 [thread overview]
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 3eb40771c00a Merge tag 'soc-fixes-7.2-3' of git://git.kern..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=16e07a79580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=1d67342c314f228d
> dashboard link: https://syzkaller.appspot.com/bug?extid=ecbb1750082f7528b507
> compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12849949580000
#syz test
--- x/drivers/usb/core/devio.c
+++ y/drivers/usb/core/devio.c
@@ -417,6 +417,7 @@ static void free_async(struct async *as)
{
int i;
+ usb_kill_urb(as->urb);
put_pid(as->pid);
if (as->cred)
put_cred(as->cred);
--
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [syzbot] KASAN: slab-use-after-free Read in vhci_send_cmd_submit
2026-08-21 4:55 ` Hillf Danton
@ 2026-08-21 5:11 ` syzbot
0 siblings, 0 replies; 6+ messages in thread
From: syzbot @ 2026-08-21 5:11 UTC (permalink / raw)
To: hdanton, linux-kernel, syzkaller-bugs
Hello,
syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in vhci_send_cmd_submit
==================================================================
BUG: KASAN: slab-use-after-free in vhci_send_cmd_submit+0xed2/0x10c0 drivers/usb/usbip/vhci_tx.c:91
Read of size 4 at addr ffff88802ae62784 by task vhci_tx/6047
CPU: 0 UID: 0 PID: 6047 Comm: vhci_tx Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0x13d/0x4b0 mm/kasan/report.c:482
kasan_report+0xdf/0x1c0 mm/kasan/report.c:595
vhci_send_cmd_submit+0xed2/0x10c0 drivers/usb/usbip/vhci_tx.c:91
vhci_tx_loop+0xff/0x460 drivers/usb/usbip/vhci_tx.c:241
kthread+0x373/0x450 kernel/kthread.c:436
ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Allocated by task 6032:
kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
kasan_save_track+0x14/0x30 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__do_kmalloc_node mm/slub.c:5337 [inline]
__kmalloc_noprof+0x324/0x820 mm/slub.c:5362
_kmalloc_noprof include/linux/slab.h:992 [inline]
usb_alloc_urb+0x66/0xa0 drivers/usb/core/urb.c:75
alloc_async drivers/usb/core/devio.c:408 [inline]
proc_do_submiturb+0x741/0x3820 drivers/usb/core/devio.c:1781
proc_submiturb drivers/usb/core/devio.c:2003 [inline]
usbdev_do_ioctl drivers/usb/core/devio.c:2703 [inline]
usbdev_ioctl+0x2ae7/0x3a90 drivers/usb/core/devio.c:2827
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl fs/ioctl.c:583 [inline]
__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 6032:
kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
kasan_save_track+0x14/0x30 mm/kasan/common.c:78
kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2678 [inline]
slab_free mm/slub.c:6372 [inline]
kfree+0x22b/0x6c0 mm/slub.c:6687
urb_destroy drivers/usb/core/urb.c:27 [inline]
kref_put include/linux/kref.h:65 [inline]
usb_free_urb.part.0+0xa5/0x110 drivers/usb/core/urb.c:96
usb_free_urb+0x1f/0x30 drivers/usb/core/urb.c:95
free_async+0x37d/0x570 drivers/usb/core/devio.c:436
proc_reapurbnonblock drivers/usb/core/devio.c:2130 [inline]
usbdev_do_ioctl drivers/usb/core/devio.c:2622 [inline]
usbdev_ioctl+0x2e7/0x3a90 drivers/usb/core/devio.c:2827
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl fs/ioctl.c:583 [inline]
__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff88802ae62700
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 132 bytes inside of
freed 192-byte region [ffff88802ae62700, ffff88802ae627c0)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2ae62
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801c0423c0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 9072505480
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1871
prep_new_page mm/page_alloc.c:1879 [inline]
get_page_from_freelist+0x110d/0x35b0 mm/page_alloc.c:3943
__alloc_frozen_pages_noprof+0x2eb/0x3300 mm/page_alloc.c:5436
alloc_slab_page mm/slub.c:3267 [inline]
allocate_slab mm/slub.c:3382 [inline]
new_slab+0xa5/0x640 mm/slub.c:3428
refill_objects+0xe3/0x410 mm/slub.c:7305
refill_sheaf mm/slub.c:2805 [inline]
__pcs_replace_empty_main+0x372/0x680 mm/slub.c:4677
alloc_from_pcs mm/slub.c:4775 [inline]
slab_alloc_node mm/slub.c:4907 [inline]
__do_kmalloc_node mm/slub.c:5336 [inline]
__kmalloc_noprof+0x66b/0x820 mm/slub.c:5362
_kmalloc_noprof include/linux/slab.h:992 [inline]
_kzalloc_noprof include/linux/slab.h:1309 [inline]
new_dir fs/proc/proc_sysctl.c:965 [inline]
get_subdir fs/proc/proc_sysctl.c:1009 [inline]
sysctl_mkdir_p fs/proc/proc_sysctl.c:1319 [inline]
__register_sysctl_table+0xbe4/0x1650 fs/proc/proc_sysctl.c:1394
register_net_sysctl_sz+0x325/0x420 net/sysctl_net.c:172
neigh_sysctl_register+0x326/0x660 net/core/neighbour.c:3915
devinet_sysctl_register+0xb6/0x210 net/ipv4/devinet.c:2781
inetdev_init+0x2b8/0x570 net/ipv4/devinet.c:291
inetdev_event+0x827/0x17f0 net/ipv4/devinet.c:1590
notifier_call_chain+0x99/0x3f0 kernel/notifier.c:85
call_netdevice_notifiers_info+0xbe/0x110 net/core/dev.c:2275
call_netdevice_notifiers_extack net/core/dev.c:2313 [inline]
call_netdevice_notifiers net/core/dev.c:2327 [inline]
register_netdevice+0x1998/0x25a0 net/core/dev.c:11541
page_owner free stack trace missing
Memory state around the buggy address:
ffff88802ae62680: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff88802ae62700: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802ae62780: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
^
ffff88802ae62800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88802ae62880: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
==================================================================
Tested on:
commit: 818bebeb drm/xe: Don't hand out the flat CCS storage a..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=148c0179580000
kernel config: https://syzkaller.appspot.com/x/.config?x=ccca94d2c01b9e78
dashboard link: https://syzkaller.appspot.com/bug?extid=ecbb1750082f7528b507
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
patch: https://syzkaller.appspot.com/x/patch.diff?x=16c30415580000
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] usbip: prevent the use of unavailable urb and hcpriv in tx
2026-08-20 14:58 [syzbot] KASAN: slab-use-after-free Read in vhci_send_cmd_submit syzbot
2026-08-21 3:13 ` Edward Adam Davis
2026-08-21 4:55 ` Hillf Danton
@ 2026-08-21 13:08 ` Edward Adam Davis
2 siblings, 0 replies; 6+ messages in thread
From: Edward Adam Davis @ 2026-08-21 13:08 UTC (permalink / raw)
To: syzbot+ecbb1750082f7528b507
Cc: gregkh, kees, valentina.manea.m, shuah, i, linux-usb,
linux-kernel, syzkaller-bugs
A race condition between TX and RX causes the URB to enter an unstable
state, triggering [1].
Similarly, a race condition exists between TX and URB reaping, leading
to [2].
In vhci_send_cmd_submit(), the URB refer count is temporarily incremented
to prevent RX or the reaping process from prematurely freeing a URB that
has not yet finished transmitting.
The priv_lock is used to protect access to hcpriv, preventing it from being
prematurely freed by RX while TX is unaware.
[1]
BUG: KASAN: slab-use-after-free in vhci_send_cmd_submit+0xed2/0x10c0 drivers/usb/usbip/vhci_tx.c:91
Read of size 4 at addr ffff888022a66584 by task vhci_tx/6044
Call Trace:
vhci_send_cmd_submit+0xed2/0x10c0 drivers/usb/usbip/vhci_tx.c:91
vhci_tx_loop+0xff/0x460 drivers/usb/usbip/vhci_tx.c:241
Allocated by task 6031:
usb_alloc_urb+0x66/0xa0 drivers/usb/core/urb.c:75
alloc_async drivers/usb/core/devio.c:408 [inline]
proc_do_submiturb+0x741/0x3820 drivers/usb/core/devio.c:1780
proc_submiturb drivers/usb/core/devio.c:2002 [inline]
usbdev_do_ioctl drivers/usb/core/devio.c:2702 [inline]
usbdev_ioctl+0x2adb/0x3aa0 drivers/usb/core/devio.c:2826
Freed by task 6031:
urb_destroy drivers/usb/core/urb.c:27 [inline]
kref_put include/linux/kref.h:65 [inline]
usb_free_urb.part.0+0xa5/0x110 drivers/usb/core/urb.c:96
usb_free_urb+0x1f/0x30 drivers/usb/core/urb.c:95
free_async+0x358/0x530 drivers/usb/core/devio.c:435
proc_reapurbnonblock drivers/usb/core/devio.c:2129 [inline]
usbdev_do_ioctl drivers/usb/core/devio.c:2621 [inline]
usbdev_ioctl+0x2e7/0x3aa0 drivers/usb/core/devio.c:2826
[2]
BUG: KASAN: slab-use-after-free in vhci_send_cmd_submit+0xe87/0x1110
Read of size 8 at addr ffff888020de4820 by task vhci_tx/9324
Call Trace:
vhci_send_cmd_submit drivers/usb/usbip/vhci_tx.c:158
vhci_tx_loop drivers/usb/usbip/vhci_tx.c:256
Allocated by task 9322:
vhci_urb_enqueue drivers/usb/usbip/vhci_hcd.c:674
usb_hcd_submit_urb drivers/usb/core/hcd.c:1542
usb_submit_urb drivers/usb/core/urb.c:586
proc_do_submiturb drivers/usb/core/devio.c:1968
usbdev_ioctl drivers/usb/core/devio.c:2003
Freed by task 9323:
pickup_urb_and_free_priv drivers/usb/usbip/vhci_rx.c:46
vhci_rx_loop drivers/usb/usbip/vhci_rx.c:66
Fixes: ddeee0b2eec2 ("USB: usbfs: properly clean up the as structure on error paths")
Fixes: 04679b3489e0 ("Staging: USB/IP: add client driver")
Reported-by: syzbot+ecbb1750082f7528b507@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=ecbb1750082f7528b507
Tested-by: syzbot+ecbb1750082f7528b507@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
---
drivers/usb/usbip/vhci_tx.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/drivers/usb/usbip/vhci_tx.c b/drivers/usb/usbip/vhci_tx.c
index 32e6fabccf72..03fc070d5825 100644
--- a/drivers/usb/usbip/vhci_tx.c
+++ b/drivers/usb/usbip/vhci_tx.c
@@ -68,7 +68,9 @@ static int vhci_send_cmd_submit(struct vhci_device *vdev)
int ret;
struct urb *urb = priv->urb;
struct usbip_header pdu_header;
+ unsigned long flags;
+ usb_get_urb(urb);
txsize = 0;
memset(&pdu_header, 0, sizeof(pdu_header));
memset(&msg, 0, sizeof(msg));
@@ -85,6 +87,7 @@ static int vhci_send_cmd_submit(struct vhci_device *vdev)
iov = kzalloc_objs(*iov, iovnum);
if (!iov) {
usbip_event_add(&vdev->ud, SDEV_EVENT_ERROR_MALLOC);
+ usb_put_urb(urb);
return -ENOMEM;
}
@@ -92,7 +95,15 @@ static int vhci_send_cmd_submit(struct vhci_device *vdev)
urb->transfer_flags |= URB_DMA_MAP_SG;
/* 1. setup usbip_header */
+ spin_lock_irqsave(&vdev->priv_lock, flags);
+ if (!urb->hcpriv) {
+ err = -EIO;
+ spin_unlock_irqrestore(&vdev->priv_lock, flags);
+ usb_put_urb(urb);
+ goto err_iso_buffer;
+ }
setup_cmd_submit_pdu(&pdu_header, urb);
+ spin_unlock_irqrestore(&vdev->priv_lock, flags);
usbip_header_correct_endian(&pdu_header, 1);
iovnum = 0;
@@ -127,6 +138,7 @@ static int vhci_send_cmd_submit(struct vhci_device *vdev)
if (!iso_buffer) {
usbip_event_add(&vdev->ud,
SDEV_EVENT_ERROR_MALLOC);
+ usb_put_urb(urb);
goto err_iso_buffer;
}
@@ -143,8 +155,10 @@ static int vhci_send_cmd_submit(struct vhci_device *vdev)
txsize);
usbip_event_add(&vdev->ud, VDEV_EVENT_ERROR_TCP);
err = -EPIPE;
+ usb_put_urb(urb);
goto err_tx;
}
+ usb_put_urb(urb);
kfree(iov);
/* This is only for isochronous case */
--
2.43.0
^ permalink raw reply related [flat|nested] 6+ messages in thread