During system shutdown, tpm_class_shutdown() when called with TPM_CHIP_FLAG_TPM2 flag set, makes chip->ops NULL. However tpm_chip_unregister() called later in shutdown sequence tries to access chip->ops in tpm_try_transmit() leading the NULL pointer dereference. This patch fixes this issue. Below is the trace for reference: BUG: unable to handle kernel NULL pointer dereference at 0000000000000048 IP: tpm_transmit+0x267/0x565 PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP NOPTI ... task: ffff937c847fe580 task.stack: ffffa79f80b04000 RIP: 0010:tpm_transmit+0x267/0x565 RSP: 0018:ffffa79f80b07c08 EFLAGS: 00010286 RAX: 0000000000000000 RBX: ffff937ca9bc8000 RCX: ffff937c847fe580 RDX: 0000000000000000 RSI: 0000000000000002 RDI: ffffffff98e3cd40 RBP: ffffa79f80b07c88 R08: 000000000001fff4 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffffa79f80b07cd4 R13: 000000000000008c R14: ffffffffffffffc3 R15: 0000000000000000 FS: 00007ef31f747740(0000) GS:ffff937caed00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000048 CR3: 00000001243d2000 CR4: 00000000001406e0 Call Trace: tpm_transmit_cmd+0x25/0x70 tpm2_shutdown+0x69/0xa3 ? __radix_tree_replace+0xd9/0x120 ? idr_replace_ext+0x92/0xb6 tpm_chip_unregister+0xaa/0xdb cr50_i2c_shutdown+0x1e/0x41 device_shutdown+0x157/0x193 kernel_power_off+0x35/0x6e SYSC_reboot+0x120/0x1a3 ? do_writepages+0x36/0x6e ? do_writepages+0x36/0x6e ? sync_inodes_one_sb+0x17/0x17 ? _raw_spin_unlock+0xe/0x20 ? iput+0x87/0x1bd do_syscall_64+0x64/0x72 entry_SYSCALL_64_after_hwframe+0x3d/0xa2 Signed-off-by: Shirish S <shirish.s@xxxxxxx> --- drivers/char/tpm/tpm-interface.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c index e32f6e8..b14d196 100644 --- a/drivers/char/tpm/tpm-interface.c +++ b/drivers/char/tpm/tpm-interface.c @@ -411,6 +411,14 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, unsigned long stop; bool need_locality; + /* chip->ops is made NULL in tpm_class_shutdown() + * This case is hit when tpm_chip_unregister() is called post + * tpm_class_shutdown(), hence exit early and return + * transmit operation not permitted + */ + if (!chip->ops) + return -EPERM; + rc = tpm_validate_command(chip, space, buf, bufsiz); if (rc == -EINVAL) return rc; -- 2.7.4
