Syzbot reports a KASAN issue as below: BUG: KASAN: use-after-free in __create_pipe include/linux/usb.h:1945 [inline] BUG: KASAN: use-after-free in send_packet+0xa2d/0xbc0 drivers/media/rc/imon.c:627 Read of size 4 at addr ffff8880256fb000 by task syz-executor314/4465
CPU: 2 PID: 4465 Comm: syz-executor314 Not tainted 6.0.0-rc1-syzkaller #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:317 [inline] print_report.cold+0x2ba/0x6e9 mm/kasan/report.c:433 kasan_report+0xb1/0x1e0 mm/kasan/report.c:495 __create_pipe include/linux/usb.h:1945 [inline] send_packet+0xa2d/0xbc0 drivers/media/rc/imon.c:627 vfd_write+0x2d9/0x550 drivers/media/rc/imon.c:991 vfs_write+0x2d7/0xdd0 fs/read_write.c:576 ksys_write+0x127/0x250 fs/read_write.c:631 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd
The iMON driver improperly releases the usb_device reference in imon_disconnect without coordinating with active users of the device.
Specifically, the fields usbdev_intf0 and usbdev_intf1 are not protected by the users counter (ictx->users). During probe, imon_init_intf0 or imon_init_intf1 increments the usb_device reference count depending on the interface. However, during disconnect, usb_put_dev is called unconditionally, regardless of actual usage.
As a result, if vfd_write or other operations are still in progress after disconnect, this can lead to a use-after-free of the usb_device pointer.
Thread 1 vfd_write Thread 2 imon_disconnect ... if usb_put_dev(ictx->usbdev_intf0) else usb_put_dev(ictx->usbdev_intf1) ... while send_packet if pipe = usb_sndintpipe( ictx->usbdev_intf0) UAF else pipe = usb_sndctrlpipe( ictx->usbdev_intf0, 0) UAF
Guard access to usbdev_intf0 and usbdev_intf1 after disconnect by checking ictx->disconnected in all writer paths. Add early return with -ENODEV in send_packet(), vfd_write(), lcd_write() and display_open() if the device is no longer present.
Set and read ictx->disconnected under ictx->lock to ensure memory synchronization. Acquire the lock in imon_disconnect() before setting the flag to synchronize with any ongoing operations.
Ensure writers exit early and safely after disconnect before the USB core proceeds with cleanup.
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
Reported-by: syzbot+f1a69784f6efe748c3bf@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=f1a69784f6efe748c3bf Fixes: 21677cfc562a ("V4L/DVB: ir-core: add imon driver") Cc: stable@vger.kernel.org
Signed-off-by: Larshin Sergey Sergey.Larshin@kaspersky.com --- drivers/media/rc/imon.c | 27 ++++++++++++++++++++------- 1 file changed, 20 insertions(+), 7 deletions(-)
diff --git a/drivers/media/rc/imon.c b/drivers/media/rc/imon.c index f5221b018808..cf3e6e43c0c7 100644 --- a/drivers/media/rc/imon.c +++ b/drivers/media/rc/imon.c @@ -536,7 +536,9 @@ static int display_open(struct inode *inode, struct file *file)
mutex_lock(&ictx->lock);
- if (!ictx->display_supported) { + if (ictx->disconnected) { + retval = -ENODEV; + } else if (!ictx->display_supported) { pr_err("display not supported by device\n"); retval = -ENODEV; } else if (ictx->display_isopen) { @@ -598,6 +600,9 @@ static int send_packet(struct imon_context *ictx) int retval = 0; struct usb_ctrlrequest *control_req = NULL;
+ if (ictx->disconnected) + return -ENODEV; + /* Check if we need to use control or interrupt urb */ if (!ictx->tx_control) { pipe = usb_sndintpipe(ictx->usbdev_intf0, @@ -949,12 +954,14 @@ static ssize_t vfd_write(struct file *file, const char __user *buf, static const unsigned char vfd_packet6[] = { 0x01, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xFF };
- if (ictx->disconnected) - return -ENODEV; - if (mutex_lock_interruptible(&ictx->lock)) return -ERESTARTSYS;
+ if (ictx->disconnected) { + retval = -ENODEV; + goto exit; + } + if (!ictx->dev_present_intf0) { pr_err_ratelimited("no iMON device present\n"); retval = -ENODEV; @@ -1029,11 +1036,13 @@ static ssize_t lcd_write(struct file *file, const char __user *buf, int retval = 0; struct imon_context *ictx = file->private_data;
- if (ictx->disconnected) - return -ENODEV; - mutex_lock(&ictx->lock);
+ if (ictx->disconnected) { + retval = -ENODEV; + goto exit; + } + if (!ictx->display_supported) { pr_err_ratelimited("no iMON display present\n"); retval = -ENODEV; @@ -2499,7 +2508,11 @@ static void imon_disconnect(struct usb_interface *interface) int ifnum;
ictx = usb_get_intfdata(interface); + + mutex_lock(&ictx->lock); ictx->disconnected = true; + mutex_unlock(&ictx->lock); + dev = ictx->dev; ifnum = interface->cur_altsetting->desc.bInterfaceNumber;