media: dvb-frontends: dib3000mb: fix uninit-value in dib3000_write_reg

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: media: dvb-frontends: dib3000mb: fix uninit-value in dib3000_write_reg Syzbot reports [1] an uninitialized value issue found by KMSAN in dib3000_read_reg(). Local u8 rb[2] is used in i2c_transfer() as a read buffer; in case that call fails, the buffer may end up with some undefined values. Since no elaborate error handling is expected in dib3000_write_reg(), simply zero out rb buffer to mitigate the problem. [1] Syzkaller report dvb-usb: bulk message failed: -22 (6/0) ===================================================== BUG: KMSAN: uninit-value in dib3000mb_attach+0x2d8/0x3c0 drivers/media/dvb-frontends/dib3000mb.c:758 dib3000mb_attach+0x2d8/0x3c0 drivers/media/dvb-frontends/dib3000mb.c:758 dibusb_dib3000mb_frontend_attach+0x155/0x2f0 drivers/media/usb/dvb-usb/dibusb-mb.c:31 dvb_usb_adapter_frontend_init+0xed/0x9a0 drivers/media/usb/dvb-usb/dvb-usb-dvb.c:290 dvb_usb_adapter_init drivers/media/usb/dvb-usb/dvb-usb-init.c:90 [inline] dvb_usb_init drivers/media/usb/dvb-usb/dvb-usb-init.c:186 [inline] dvb_usb_device_init+0x25a8/0x3760 drivers/media/usb/dvb-usb/dvb-usb-init.c:310 dibusb_probe+0x46/0x250 drivers/media/usb/dvb-usb/dibusb-mb.c:110 ... Local variable rb created at: dib3000_read_reg+0x86/0x4e0 drivers/media/dvb-frontends/dib3000mb.c:54 dib3000mb_attach+0x123/0x3c0 drivers/media/dvb-frontends/dib3000mb.c:758 ...

References

• https://git.kernel.org/stable/c/035772fcd631eee2756b31cb6df249c0a8d453d7
• https://git.kernel.org/stable/c/e11778189513cd7fb2edced5bd053bc18ede8418
• https://git.kernel.org/stable/c/53106510736e734ce8b731ba871363389bfbf4c9
• https://git.kernel.org/stable/c/3876e3a1c31a58a352c6bf5d2a90e3304445a637
• https://git.kernel.org/stable/c/1d6de21f00293d819b5ca6dbe75ff1f3b6392140
• https://git.kernel.org/stable/c/c1197c1457bb7098cf46366e898eb52b41b6876a
• https://git.kernel.org/stable/c/2dd59fe0e19e1ab955259978082b62e5751924c7