On Fri, 25 Sep 2020 at 07:56, Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote: > > On Tue, Sep 22, 2020 at 11:41:28AM +0200, Ard Biesheuvel wrote: > > The TPM event log is provided to the OS by the firmware, by loading > > it into an area in memory and passing the physical address via a node > > in the device tree. > > > > Currently, we use __va() to access the memory via the kernel's linear > > map: however, it is not guaranteed that the linear map covers this > > particular address, as we may be running under HIGHMEM on a 32-bit > > architecture, or running firmware that uses a memory type for the > > event log that is omitted from the linear map (such as EfiReserved). > > Makes perfect sense to the level that I wonder if this should have a > fixes tag and/or needs to be backported to the stable kernels? > AIUI, the code was written specifically for ppc64, which is a non-highmem, non-EFI architecture. However, when we start reusing this driver for ARM, this issue could pop up. The code itself has been refactored a couple of times, so I think it will require different versions of the patch for different generations of stable kernels. So perhaps just add Cc: <stable@xxxxxxxxxxxxxxx>, and wait and see how far back it applies cleanly? > > So instead, use memremap(), which will reuse the linear mapping if > > it is valid, or create another mapping otherwise. > > > > Cc: Peter Huewe <peterhuewe@xxxxxx> > > Cc: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> > > Cc: Jason Gunthorpe <jgg@xxxxxxxx> > > Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> > > --- > > drivers/char/tpm/eventlog/of.c | 8 +++++++- > > 1 file changed, 7 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/char/tpm/eventlog/of.c b/drivers/char/tpm/eventlog/of.c > > index a9ce66d09a75..9178547589a3 100644 > > --- a/drivers/char/tpm/eventlog/of.c > > +++ b/drivers/char/tpm/eventlog/of.c > > @@ -11,6 +11,7 @@ > > */ > > > > #include <linux/slab.h> > > +#include <linux/io.h> > > #include <linux/of.h> > > #include <linux/tpm_eventlog.h> > > > > @@ -25,6 +26,7 @@ int tpm_read_log_of(struct tpm_chip *chip) > > struct tpm_bios_log *log; > > u32 size; > > u64 base; > > + void *p; > > I'd just use 'ptr' for readability sake. > If you prefer > > log = &chip->log; > > if (chip->dev.parent && chip->dev.parent->of_node) > > @@ -65,7 +67,11 @@ int tpm_read_log_of(struct tpm_chip *chip) > > return -EIO; > > } > > > > - log->bios_event_log = kmemdup(__va(base), size, GFP_KERNEL); > > + p = memremap(base, size, MEMREMAP_WB); > > + if (!p) > > + return -ENOMEM; > > + log->bios_event_log = kmemdup(p, size, GFP_KERNEL); > > + memunmap(p); > > if (!log->bios_event_log) > > return -ENOMEM; > > > > -- > > 2.17.1 > > > > This is a really great catch! > > I'm a bit late of my PR a bit because of SGX upstreaming madness > (sending v39 soon). If you can answer to my question above, I can do > that nitpick change to patch and get it to my v5.10 PR. > Yes, please. > PS. Just so that you know, once I've applied it, it will be available > here: > > git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git > > I'll include MAINTAINERS update to that PR. > > /Jarkko
