On Tue, Jun 15, 2021 at 03:18:48PM +0200, Jarkko Sakkinen wrote: > On Tue, Jun 15, 2021 at 11:14:09AM +0200, Vincent Whitchurch wrote: > > If the tpm_tis module is removed (or a system shutdown is triggered) > > while the tpmrm device is use, the kernel crashes due to chip->ops being > > NULL: > > > > # exec 3<>/dev/tpmrm0 > > # rmmod tpm_tis > > # exit > > ================================================================== > > BUG: KASAN: null-ptr-deref in tpm_chip_start+0x2d/0x120 [tpm] > > Read of size 8 at addr 0000000000000060 by task sh/994 > > > > Call Trace: > > kasan_report.cold.13+0x10f/0x111 > > tpm_chip_start+0x2d/0x120 [tpm] > > tpm2_del_space+0x2c/0xa0 [tpm] > > tpmrm_release+0x3f/0x50 [tpm] > > __fput+0x110/0x3c0 > > task_work_run+0x94/0xd0 > > do_exit+0x683/0x13e0 > > do_group_exit+0x8b/0x140 > > do_syscall_64+0x3c/0x80 > > ================================================================== > > > > Fix this by making tpm2_del_space() use tpm_try_get_ops(). The latter > > already includes the calls to tpm_chip_start() and tpm_chip_stop(). > > This lacks explanation why migrating to tpm_try_get_ops() fixes the > issue. Saying that doing something fixes something is not good enough > explanation. So, can you extend this paragraph just a bit in the next > version? Thank you for the review, but I see now that James already proposed a more-or-less identical fix earlier, so I'll let that patch run its due course: https://lore.kernel.org/linux-integrity/e7566e1e48f5be9dca034b4bfb67683b5d3cb88f.camel@xxxxxxxxxxxxxxxxxxxxx/ https://lore.kernel.org/linux-integrity/327f4c87-e652-6cbe-c624-16a6edf0c31d@xxxxxxxxxx/
