syzbot reports a KASAN issue as below:
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000019: 0000 [#1] SMP KASAN PTI KASAN: null-ptr-deref in range [0x00000000000000c8-0x00000000000000cf] CPU: 1 UID: 0 PID: 5849 Comm: syz-executor279 Not tainted 6.15.0-rc2-syzkaller #0 PREEMPT(full) Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 RIP: 0010:__mutex_lock_common kernel/locking/mutex.c:580 [inline] RIP: 0010:__mutex_lock+0x15d/0x10c0 kernel/locking/mutex.c:746 Call Trace: <TASK> dvb_usbv2_generic_write+0x26/0x50 mxl111sf_ctrl_msg+0x172/0x2e0 mxl111sf_write_reg+0xda/0x1f0 mxl111sf_i2c_start mxl111sf_i2c_sw_xfer_msg mxl111sf_i2c_xfer+0x923/0x8aa0 __i2c_transfer+0x859/0x2250 i2c_transfer+0x2c2/0x430 i2c_transfer_buffer_flags+0x182/0x260 i2c_master_recv i2cdev_read+0x10a/0x220 vfs_read+0x21f/0xb90 ksys_read+0x19d/0x2d0 do_syscall_x64 do_syscall_64+0xf3/0x230 entry_SYSCALL_64_after_hwframe+0x77/0x7f </TASK>
This occurs due to a race condition during DVB-USB-V2 device initialization. While initialization is in progress, I2C data may be read from userspace, leading to a NULL pointer dereference in dvb_usbv2_generic_write and a kernel panic.
Thread 1 (probe device) Thread 2 (receive i2c data) ... dvb_usbv2_probe() ... d->priv = kzalloc( d->props->size_of_priv, GFP_KERNEL); ... dvb_usbv2_init() ... // can read data from i2c dvb_usbv2_i2c_init() ... ... i2cdev_read() ... // d->priv data is invalid. UB mxl111sf_i2c_xfer() ... mxl111sf_ctrl_msg() ... // null ptr deref dvb_usbv2_generic_write() ... ... // d->priv data is valid dvb_usbv2_adapter_init() ...
Add init_ready flag check to prevent I/O on uninitialized DVB-USB-V2 device.
Reported-by: syzbot+f9f5333782a854509322@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=f9f5333782a854509322 Fixes: 4c66c9205c07 ("[media] dvb-usb: add ATSC support for the Hauppauge WinTV-Aero-M") Cc: stable@vger.kernel.org Signed-off-by: Nalivayko Sergey Sergey.Nalivayko@kaspersky.com --- drivers/media/usb/dvb-usb-v2/mxl111sf-i2c.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/media/usb/dvb-usb-v2/mxl111sf-i2c.c b/drivers/media/usb/dvb-usb-v2/mxl111sf-i2c.c index 100a1052dcbc..b7bad90b16dc 100644 --- a/drivers/media/usb/dvb-usb-v2/mxl111sf-i2c.c +++ b/drivers/media/usb/dvb-usb-v2/mxl111sf-i2c.c @@ -804,7 +804,7 @@ int mxl111sf_i2c_xfer(struct i2c_adapter *adap, int hwi2c = (state->chip_rev > MXL111SF_V6); int i, ret;
- if (mutex_lock_interruptible(&d->i2c_mutex) < 0) + if (!atomic_read(&d->init_ready) || mutex_lock_interruptible(&d->i2c_mutex) < 0) return -EAGAIN;
for (i = 0; i < num; i++) {