NAK: [PATCH][SRU][B,E,F] Fix oops on access of ACPI BERT table on ARM64

[Sultan Alsawaf]

There's a V2, so nak this.

On Tue, Mar 17, 2020 at 03:22:43PM +0000, Colin King wrote:
> From: Colin Ian King <colin.king at canonical.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1866772
> 
> == SRU Request [ BIONIC, EOAN, FOCAL ] ==
> 
> Reading /sys/firmware/acpi/tables/data/BERT as root at at odd byte offset
> will cause an oops. This is because the source address is I/O mapped and
> this needs to be read with an I/O memcpy rather than an memcpy.
> 
> Issue found using the latest stress-ng
> 
> == Fix ==
> 
> The fix is upstream (linux-next) commit that will land in 5.7, the
> backport to bionic, eoan and focal is just a minor context wiggle.
> The commit in question is:
> 
> commit 08c07cefb3042a55bc9f8243814b504d5eff93f3
> Author: Colin Ian King <colin.king at canonical.com>
> Date: Thu Mar 12 11:13:45 2020 +0000
> 
>     ACPI: sysfs: copy ACPI data using io memory copying
> 
> == Test ==
> 
> Running on hotdog with the reproducer below (run as root):
> 
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <fcntl.h>
> #include <unistd.h>
> #include <errno.h>
> #include <stdio.h>
> #include <string.h>
> 
> int main(void)
> {
>         int fd;
>         char buffer[3];
>         ssize_t n;
> 
>         fd = open("/sys/firmware/acpi/tables/data/BERT", O_RDONLY);
>         if (fd < 0) {
>                 fprintf(stderr, "open failed: %d (%s)\n", errno, strerror(errno));
>                 return -1;
>         }
>         do {
>                 n = read(fd, buffer, sizeof(buffer));
>         } while (n > 0);
> 
>         return 0;
> }
> 
> Without the fix it will oops. With the fix it works OK.
> 
> == Regession Potential ==
> 
> This only affects the reading of the ACPI BERT table from /sys as root
> at an odd offset, generally this data is read in natually aligned
> offsets so it is limited in scope to just a very narrow use case.
> Normally the ACPI BERT table is just handled by the kernel, so access
> to this table is just for debugging purposes.
> 
> Colin Ian King (1):
>   ACPI: sysfs: copy ACPI data using io memory copying
> 
>  drivers/acpi/sysfs.c   |  2 +-
>  fs/libfs.c             | 33 +++++++++++++++++++++++++++++++++
>  include/linux/string.h |  2 ++
>  3 files changed, 36 insertions(+), 1 deletion(-)
> 
> -- 
> 2.7.4
> 
> 
> -- 
> kernel-team mailing list
> kernel-team at lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/kernel-team