| Message ID | d60ce7dd74704b0ca0a857186f30de4006b63534.1537355312.git.christophe.leroy@c-s.fr (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2,1/2] sched: move stack_canary field at the top of task_struct | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | next/apply_patch Successfully applied |
| snowpatch_ozlabs/checkpatch | success | Test checkpatch on branch next |
On Wed, Sep 19, 2018 at 11:14:43AM +0000, Christophe Leroy wrote: > In order to allow the use of non global stack protector canary, > the stack canary needs to be located at a know offset defined > in Makefile via -mstack-protector-guard-offset. > > On powerpc/32, register r2 points to current task_struct at > all time, the stack_canary located inside task_struct can be > used directly if it is located in a known place. > > In order to allow that, this patch moves the stack_canary field > out of the randomized area of task_struct. And you cannot use something like asm-offsets to extract this? > Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> > --- > include/linux/sched.h | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index 977cb57d7bc9..1d977b8a4bac 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -601,6 +601,10 @@ struct task_struct { > /* -1 unrunnable, 0 runnable, >0 stopped: */ > volatile long state; > > +#ifdef CONFIG_STACKPROTECTOR > + /* Canary value for the -fstack-protector GCC feature: */ > + unsigned long stack_canary; > +#endif > /* > * This begins the randomizable portion of task_struct. Only > * scheduling-critical items should be added above here. Might as well put it before state, right after the task_info thing.
Le 19/09/2018 à 13:58, Peter Zijlstra a écrit : > On Wed, Sep 19, 2018 at 11:14:43AM +0000, Christophe Leroy wrote: >> In order to allow the use of non global stack protector canary, >> the stack canary needs to be located at a know offset defined >> in Makefile via -mstack-protector-guard-offset. >> >> On powerpc/32, register r2 points to current task_struct at >> all time, the stack_canary located inside task_struct can be >> used directly if it is located in a known place. >> >> In order to allow that, this patch moves the stack_canary field >> out of the randomized area of task_struct. > > And you cannot use something like asm-offsets to extract this? I have not been able to find a way to define the compilation flags AFTER building asm-offsets.h, see https://patchwork.ozlabs.org/patch/971521/ If you have a suggestion, it is welcomed. > >> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> >> --- >> include/linux/sched.h | 8 ++++---- >> 1 file changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/include/linux/sched.h b/include/linux/sched.h >> index 977cb57d7bc9..1d977b8a4bac 100644 >> --- a/include/linux/sched.h >> +++ b/include/linux/sched.h >> @@ -601,6 +601,10 @@ struct task_struct { >> /* -1 unrunnable, 0 runnable, >0 stopped: */ >> volatile long state; >> >> +#ifdef CONFIG_STACKPROTECTOR >> + /* Canary value for the -fstack-protector GCC feature: */ >> + unsigned long stack_canary; >> +#endif >> /* >> * This begins the randomizable portion of task_struct. Only >> * scheduling-critical items should be added above here. > > Might as well put it before state, right after the task_info thing. > Yes, it doesn't make much difference, don't any arch expect state at offset 0 ? Christophe
On Wed, Sep 19, 2018 at 02:25:00PM +0200, Christophe LEROY wrote: > I have not been able to find a way to define the compilation flags AFTER > building asm-offsets.h, see https://patchwork.ozlabs.org/patch/971521/ > > If you have a suggestion, it is welcomed. Not really; I always get lost in that stuff :/ > > Might as well put it before state, right after the task_info thing. > > > > Yes, it doesn't make much difference, don't any arch expect state at offset > 0 ? Uhmm.. dunno. I would not expect so, but then I didn't check.
Christophe LEROY <christophe.leroy@c-s.fr> writes: > Le 19/09/2018 à 13:58, Peter Zijlstra a écrit : >> On Wed, Sep 19, 2018 at 11:14:43AM +0000, Christophe Leroy wrote: >>> In order to allow the use of non global stack protector canary, >>> the stack canary needs to be located at a know offset defined >>> in Makefile via -mstack-protector-guard-offset. >>> >>> On powerpc/32, register r2 points to current task_struct at >>> all time, the stack_canary located inside task_struct can be >>> used directly if it is located in a known place. >>> >>> In order to allow that, this patch moves the stack_canary field >>> out of the randomized area of task_struct. >> >> And you cannot use something like asm-offsets to extract this? > > I have not been able to find a way to define the compilation flags AFTER > building asm-offsets.h, see https://patchwork.ozlabs.org/patch/971521/ > > If you have a suggestion, it is welcomed. Hmm, that's something of a hard problem. But the stack canary is one of the things we really *do* want to be randomised, so we should probably try to come up with a solution. cheers
diff --git a/include/linux/sched.h b/include/linux/sched.h index 977cb57d7bc9..1d977b8a4bac 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -601,6 +601,10 @@ struct task_struct { /* -1 unrunnable, 0 runnable, >0 stopped: */ volatile long state; +#ifdef CONFIG_STACKPROTECTOR + /* Canary value for the -fstack-protector GCC feature: */ + unsigned long stack_canary; +#endif /* * This begins the randomizable portion of task_struct. Only * scheduling-critical items should be added above here. @@ -746,10 +750,6 @@ struct task_struct { pid_t pid; pid_t tgid; -#ifdef CONFIG_STACKPROTECTOR - /* Canary value for the -fstack-protector GCC feature: */ - unsigned long stack_canary; -#endif /* * Pointers to the (original) parent process, youngest child, younger sibling, * older sibling, respectively. (p->father can be replaced with
In order to allow the use of non global stack protector canary, the stack canary needs to be located at a know offset defined in Makefile via -mstack-protector-guard-offset. On powerpc/32, register r2 points to current task_struct at all time, the stack_canary located inside task_struct can be used directly if it is located in a known place. In order to allow that, this patch moves the stack_canary field out of the randomized area of task_struct. Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> --- include/linux/sched.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)