Messages in this thread | | | Date | Tue, 21 Dec 2021 09:01:06 -0500 | Subject | Re: [PATCH] tpm: Fix kexec crash due to access to ops NULL pointer (powerpc) | From | Stefan Berger <> |
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On 12/21/21 03:47, Jarkko Sakkinen wrote: > On Sat, Dec 11, 2021 at 08:28:04PM -0500, Stefan Berger wrote: >> Fix the following crash on kexec by checking chip->ops for a NULL pointer >> in tpm_chip_start() and returning an error code if this is the case. >> >> BUG: Kernel NULL pointer dereference on read at 0x00000060 >> Faulting instruction address: 0xc00000000099a06c >> Oops: Kernel access of bad area, sig: 11 [#1] >> ... >> NIP [c00000000099a06c] tpm_chip_start+0x2c/0x140 >> LR [c00000000099a808] tpm_chip_unregister+0x108/0x170 >> Call Trace: >> [c0000000188bfa00] [c000000002b03930] fw_devlink_strict+0x0/0x8 (unreliable) >> [c0000000188bfa30] [c00000000099a808] tpm_chip_unregister+0x108/0x170 >> [c0000000188bfa70] [c0000000009a3874] tpm_ibmvtpm_remove+0x34/0x130 >> [c0000000188bfae0] [c000000000110dbc] vio_bus_remove+0x5c/0xb0 >> [c0000000188bfb20] [c0000000009bc154] device_shutdown+0x1d4/0x3a8 >> [c0000000188bfbc0] [c000000000196e14] kernel_restart_prepare+0x54/0x70 >> >> The referenced patch below introduced a function to shut down the VIO bus. >> The bus shutdown now calls tpm_del_char_device (via tpm_chip_unregister) >> after a call to tpm_class_shutdown, which already set chip->ops to NULL. >> The crash occurrs when tpm_del_char_device calls tpm_chip_start with the >> chip->ops NULL pointer. >> >> Fixes: 39d0099f9439 ("powerpc/pseries: Add shutdown() to vio_driver and vio_bus") >> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com> >> --- >> drivers/char/tpm/tpm-chip.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c >> index ddaeceb7e109..cca1bde296ee 100644 >> --- a/drivers/char/tpm/tpm-chip.c >> +++ b/drivers/char/tpm/tpm-chip.c >> @@ -101,6 +101,9 @@ int tpm_chip_start(struct tpm_chip *chip) >> { >> int ret; >> >> + if (!chip->ops) >> + return -EINVAL; > This triggers to all drivers, not just tpm_ibmvtpm, i.e. the fix has > side-effects.
What are those side-effects?
Stefan
> > /Jarkko >
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