Messages in this thread | | | Date | Tue, 5 Dec 2017 13:14:17 +0000 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH] Arm: mm: ftrace: Only set text back to ro after kernel has been marked ro |
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On Tue, Dec 05, 2017 at 12:47:09PM +0100, Matthias Reichl wrote: > On Wed, Aug 23, 2017 at 03:03:51PM -0400, Steven Rostedt wrote: > > On Wed, 23 Aug 2017 11:48:13 -0700 > > Kees Cook <keescook@chromium.org> wrote: > > > > > > diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c > > > > index ad80548..fd75f38 100644 > > > > --- a/arch/arm/mm/init.c > > > > +++ b/arch/arm/mm/init.c > > > > @@ -745,19 +745,29 @@ static int __mark_rodata_ro(void *unused) > > > > return 0; > > > > } > > > > > > > > +static int kernel_set_to_readonly; > > > > > > Adding a comment here might be a good idea, something like: > > > > > > /* Has system boot-up reached mark_rodata_ro() yet? */ > > > > I don't mind adding a comment, but the above is rather self explanatory > > (one can easily see that it is set in mark_rodata_ro() with a simple > > search). > > > > If a comment is to be added, something a bit more descriptive of the > > functionality of the variable would be appropriate: > > > > /* > > * Ignore modifying kernel text permissions until the kernel core calls > > * make_rodata_ro() at system start up. > > */ > > > > I can resend with the comment, or whoever takes this could add it > > themselves. > > Gentle ping: this patch doesn't seem to have landed in upstream > trees yet. Is any more work required? > > It would be nice to have this fix added. Just tested next-20171205 > on RPi B+, it oopses when the function tracer is enabled during boot. > next-20171205 plus this patch boots up fine.
When does it oops?
Reading through this code, I'm left wondering why we switch the rodata section to be writable here - if we're poking at kernel text, then surely we shouldn't be the read-only data read-write?
Should kernel_set_to_readonly also be a rodata-after-init variable?
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