Messages in this thread | | | Date | Wed, 28 Oct 2015 09:12:40 +0900 | From | Greg KH <> | Subject | Re: [PATCH] lkdtm: fix ACCESS_USERSPACE test |
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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 <sds@tycho.nsa.gov> > --- > 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)?
thanks,
greg k-h
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