Hi, > Gesendet: Dienstag, 28. September 2021 um 22:08 Uhr > Von: "Mark Brown" <broonie@xxxxxxxxxx> > An: "Lino Sanfilippo" <LinoSanfilippo@xxxxxx> > Cc: f.fainelli@xxxxxxxxx, rjui@xxxxxxxxxxxx, sbranden@xxxxxxxxxxxx, bcm-kernel-feedback-list@xxxxxxxxxxxx, nsaenz@xxxxxxxxxx, linux-spi@xxxxxxxxxxxxxxx, linux-rpi-kernel@xxxxxxxxxxxxxxxxxxx, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, jgg@xxxxxxxx, p.rosenberger@xxxxxxxxxx, linux-integrity@xxxxxxxxxxxxxxx, stable@xxxxxxxxxxxxxxx > Betreff: Re: [PATCH] spi: bcm2835: do not unregister controller in shutdown handler > > On Tue, Sep 28, 2021 at 09:56:57PM +0200, Lino Sanfilippo wrote: > > Do not unregister the SPI controller in the shutdown handler. The reason > > to avoid this is that controller unregistration results in the slave > > devices remove() handler being called which may be unexpected for slave > > drivers at system shutdown. > > > > One example is if the BCM2835 driver is used together with the TPM SPI > > driver: > > At system shutdown first the TPM chip devices (pre) shutdown handler > > (tpm_class_shutdown) is called, stopping the chip and setting an operations > > pointer to NULL. > > Then since the BCM2835 shutdown handler unregisters the SPI controller the > > TPM SPI remove function (tpm_tis_spi_remove) is also called. In case of > > TPM 2 this function accesses the now nullified operations pointer, > > resulting in the following NULL pointer access: > > > > [ 174.078277] 8<--- cut here --- > > [ 174.078288] Unable to handle kernel NULL pointer dereference at virtual address 00000034 > > [ 174.078293] pgd = 557a5fc9 > > [ 174.078300] [00000034] *pgd=031cf003, *pmd=00000000 > > [ 174.078317] Internal error: Oops: 206 [#1] SMP ARM > > [ 174.078323] Modules linked in: tpm_tis_spi tpm_tis_core tpm spidev gpio_pca953x mcp320x rtc_pcf2127 industrialio regmap_i2c regmap_spi 8021q garp stp llc ftdi_sio6 > > Please think hard before including complete backtraces in upstream > reports, they are very large and contain almost no useful information > relative to their size so often obscure the relevant content in your > message. If part of the backtrace is usefully illustrative (it often is > for search engines if nothing else) then it's usually better to pull out > the relevant sections. > Thank you for the feedback, I will omit the stack trace in the next version. Regards, Lino
