Hi,
On Tue, Aug 06, 2024 at 02:43:57PM +0100, Joey Gouly wrote:
> On Tue, Aug 06, 2024 at 02:33:37PM +0100, Dave Martin wrote:
> > Hi,
> >
> > On Thu, Aug 01, 2024 at 05:01:10PM +0100, Joey Gouly wrote:
> > > On Thu, Jul 25, 2024 at 04:57:09PM +0100, Dave Martin wrote:
> > > > On Fri, May 03, 2024 at 02:01:33PM +0100, Joey Gouly wrote:
> > > > > If a memory fault occurs that is due to an overlay/pkey fault, report that to
> > > > > userspace with a SEGV_PKUERR.
> > > > >
> > > > > Signed-off-by: Joey Gouly <joey.gouly@xxxxxxx>
> > > > > Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> > > > > Cc: Will Deacon <will@xxxxxxxxxx>
> > > > > ---
> > > > > arch/arm64/include/asm/traps.h | 1 +
> > > > > arch/arm64/kernel/traps.c | 12 ++++++--
> > > > > arch/arm64/mm/fault.c | 56 ++++++++++++++++++++++++++++++++--
> > > > > 3 files changed, 64 insertions(+), 5 deletions(-)
[...]
> > > > > diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> > > > > index 215e6d7f2df8..1bac6c84d3f5 100644
> > > > > --- a/arch/arm64/kernel/traps.c
> > > > > +++ b/arch/arm64/kernel/traps.c
> > > > > @@ -263,16 +263,24 @@ static void arm64_show_signal(int signo, const char *str)
> > > > > __show_regs(regs);
> > > > > }
> > > > >
> > > > > -void arm64_force_sig_fault(int signo, int code, unsigned long far,
> > > > > - const char *str)
> > > > > +void arm64_force_sig_fault_pkey(int signo, int code, unsigned long far,
> > > > > + const char *str, int pkey)
> > > > > {
> > > > > arm64_show_signal(signo, str);
> > > > > if (signo == SIGKILL)
> > > > > force_sig(SIGKILL);
> > > > > + else if (code == SEGV_PKUERR)
> > > > > + force_sig_pkuerr((void __user *)far, pkey);
> > > >
> > > > Is signo definitely SIGSEGV here? It looks to me like we can get in
> > > > here for SIGBUS, SIGTRAP etc.
> > > >
> > > > si_codes are not unique between different signo here, so I'm wondering
> > > > whether this should this be:
> > > >
> > > > else if (signo == SIGSEGV && code == SEGV_PKUERR)
> > > >
> > > > ...?
> > > >
> > > >
> > > > > else
> > > > > force_sig_fault(signo, code, (void __user *)far);
> > > > > }
> > > > >
> > > > > +void arm64_force_sig_fault(int signo, int code, unsigned long far,
> > > > > + const char *str)
> > > > > +{
> > > > > + arm64_force_sig_fault_pkey(signo, code, far, str, 0);
> > > >
> > > > Is there a reason not to follow the same convention as elsewhere, where
> > > > -1 is passed for "no pkey"?
> > > >
> > > > If we think this should never be called with signo == SIGSEGV &&
> > > > code == SEGV_PKUERR and no valid pkey but if it's messy to prove, then
> > > > maybe a WARN_ON_ONCE() would be worth it here?
> > > >
> > >
> > > Anshuman suggested to separate them out, which I did like below, I think that
> > > addresses your comments too?
> > >
> > > diff --git arch/arm64/kernel/traps.c arch/arm64/kernel/traps.c
> > > index 215e6d7f2df8..49bac9ae04c0 100644
> > > --- arch/arm64/kernel/traps.c
> > > +++ arch/arm64/kernel/traps.c
> > > @@ -273,6 +273,13 @@ void arm64_force_sig_fault(int signo, int code, unsigned long far,
> > > force_sig_fault(signo, code, (void __user *)far);
> > > }
> > >
> > > +void arm64_force_sig_fault_pkey(int signo, int code, unsigned long far,
> > > + const char *str, int pkey)
> > > +{
> > > + arm64_show_signal(signo, str);
> > > + force_sig_pkuerr((void __user *)far, pkey);
> > > +}
> > > +
> > > void arm64_force_sig_mceerr(int code, unsigned long far, short lsb,
> > > const char *str)
> > > {
> > >
> > > diff --git arch/arm64/mm/fault.c arch/arm64/mm/fault.c
> > > index 451ba7cbd5ad..1ddd46b97f88 100644
> > > --- arch/arm64/mm/fault.c
> > > +++ arch/arm64/mm/fault.c
> >
> > (Guessing where this is means to apply, since there is no hunk header
> > or context...)
>
> Sorry I had some other changes and just mashed the bits into a diff-looking-thing.
Fair enough. There are a few similar bits of code, so including more
lines of context would have been helpful.
The change looked reasonable though.
> > >
> > > - arm64_force_sig_fault(SIGSEGV, si_code, far, inf->name);
> > > + if (si_code == SEGV_PKUERR)
> > > + arm64_force_sig_fault_pkey(SIGSEGV, si_code, far, inf->name, pkey);
> >
> > Maybe drop the the signo and si_code argument? This would mean that
> > arm64_force_sig_fault_pkey() can't be called with a signo/si_code
> > combination that makes no sense.
> >
> > I think pkey faults are always going to be SIGSEGV/SEGV_PKUERR, right?
> > Or are there other combinations that can apply for these faults?
>
> Ah yes, I can simplify it even more, thanks.
>
> diff --git arch/arm64/kernel/traps.c arch/arm64/kernel/traps.c
> index 49bac9ae04c0..d9abb8b390c0 100644
> --- arch/arm64/kernel/traps.c
> +++ arch/arm64/kernel/traps.c
> @@ -273,10 +273,9 @@ void arm64_force_sig_fault(int signo, int code, unsigned long far,
> force_sig_fault(signo, code, (void __user *)far);
> }
>
> -void arm64_force_sig_fault_pkey(int signo, int code, unsigned long far,
> - const char *str, int pkey)
> +void arm64_force_sig_fault_pkey(unsigned long far, const char *str, int pkey)
> {
> - arm64_show_signal(signo, str);
> + arm64_show_signal(SIGSEGV, str);
> force_sig_pkuerr((void __user *)far, pkey);
> }
Looks sensible.
I see that force_sig_pkuerr() fills in the signo and si_code itself.
Cheers
---Dave
