On 10/27/2015 08:12 PM, Greg KH wrote:
On Tue, Oct 27, 2015 at 04:47:53PM -0400, Stephen Smalley wrote:
Add a copy_to_user() call to the ACCESS_USERSPACE test
prior to attempting direct dereferencing of the user
address to ensure the page is present. Otherwise,
a fault occurs on arm kernels even prior to the introduction
of CONFIG_CPU_SW_DOMAIN_PAN, and there is no difference in
behavior for CONFIG_CPU_SW_DOMAIN_PAN=n vs CONFIG_CPU_SW_DOMAIN_PAN=y.
Before this change, for any value of CONFIG_CPU_SW_DOMAIN_PAN:
lkdtm: Performing direct entry ACCESS_USERSPACE
lkdtm: attempting bad read at b6fe8000
Unable to handle kernel paging request at virtual address b6fe8000
After this change, for CONFIG_CPU_SW_DOMAIN_PAN=n:
lkdtm: Performing direct entry ACCESS_USERSPACE
lkdtm: attempting bad read at b6efc000
lkdtm: attempting bad write at b6efc000
After this change, for CONFIG_CPU_SW_DOMAIN_PAN=y:
lkdtm: Performing direct entry ACCESS_USERSPACE
lkdtm: attempting bad read at b6f7d000
Unhandled fault: page domain fault (0x01b) at 0xb6f7d000
...
Signed-off-by: Stephen Smalley <[email protected]>
---
drivers/misc/lkdtm.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
Should this also be applied to older kernels (i.e. a stable fix)?
I don't think it qualifies (only a fix for a kernel crash test), but will defer
to Kees.
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