On Mon, Nov 26, 2018 at 11:43 PM, Greg Kroah-Hartman <gre...@linuxfoundation.org> wrote: > On Wed, Nov 07, 2018 at 08:14:10PM +0000, Christophe Leroy wrote: >> Today, when doing a lkdtm test before the readiness of the >> random generator, (ptrval) is printed instead of the address >> at which it perform the fault: >> >> [ 1597.337030] lkdtm: Performing direct entry EXEC_USERSPACE >> [ 1597.337142] lkdtm: attempting ok execution at (ptrval) >> [ 1597.337398] lkdtm: attempting bad execution at (ptrval) >> [ 1597.337460] kernel tried to execute user page (77858000) -exploit >> attempt? (uid: 0) >> [ 1597.344769] Unable to handle kernel paging request for instruction fetch >> [ 1597.351392] Faulting instruction address: 0x77858000 >> [ 1597.356312] Oops: Kernel access of bad area, sig: 11 [#1] >> >> If the lkdtm test is done later on, it prints an hashed address. >> >> In both cases this is pointless. The purpose of the test is to >> ensure the kernel generates an Oops at the expected address, >> so real addresses needs to be printed. This patch fixes that. > > I am pretty sure this is intentional. Kees?
I've gone back and forth on this and in the end I decided I'd wait and see if anyone was bothered by it besides just me. :) But, yes, for lkdtm do really do want a "real" view of the pointer because we're comparing it against page tables and/or kernel section layout, etc. I've applied this to my lkdtm -next tree. Thanks! -- Kees Cook
