| Message ID | 20170324135356.25881-1-msalter@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Mar 24, 2017 at 09:53:56AM -0400, Mark Salter wrote: > Commit 5c492c3f5255 ("arm64: smp: Add function to determine if cpus are > stuck in the kernel") added a helper function to determine if die() is > supported in cpu_ops. This function assumes a cpu will have a valid > cpu_ops entry, but that may not be the case for cpu0 is spin-table or > parking protocol is used to boot secondary cpus. In that case, there > is a NULL dereference if have_cpu_die() is called by cpu0. So add a > check for a valid cpu_ops before dereferencing it. > > Fixes: 5c492c3f5255 ("arm64: smp: Add function to determine if cpus are stuck in the kernel") > Signed-off-by: Mark Salter <msalter@redhat.com> > --- > arch/arm64/kernel/smp.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > index ef1caae..9b10365 100644 > --- a/arch/arm64/kernel/smp.c > +++ b/arch/arm64/kernel/smp.c > @@ -944,7 +944,7 @@ static bool have_cpu_die(void) > #ifdef CONFIG_HOTPLUG_CPU > int any_cpu = raw_smp_processor_id(); > > - if (cpu_ops[any_cpu]->cpu_die) > + if (cpu_ops[any_cpu] && cpu_ops[any_cpu]->cpu_die) > return true; We take similar care in op_cpu_disable() and cpu_die_early(), so this is certainly more in keeping with the rest of the arm64 code, and is an improvement. ... however, I think there is a larger problem. Given cpu_ops can differ by CPU, we could encounter a case where some CPUs had PSCI ops, and some had none. In that case, have_cpu_die() can return different values on different CPUs. ... which means that cpus_are_stuck_in_kernel() is on shaky ground, and we may need a more comprehensive fix. Thanks, Mark.
On Fri, 2017-03-24 at 14:09 +0000, Mark Rutland wrote: > On Fri, Mar 24, 2017 at 09:53:56AM -0400, Mark Salter wrote: > > Commit 5c492c3f5255 ("arm64: smp: Add function to determine if cpus are > > stuck in the kernel") added a helper function to determine if die() is > > supported in cpu_ops. This function assumes a cpu will have a valid > > cpu_ops entry, but that may not be the case for cpu0 is spin-table or > > parking protocol is used to boot secondary cpus. In that case, there > > is a NULL dereference if have_cpu_die() is called by cpu0. So add a > > check for a valid cpu_ops before dereferencing it. > > > > Fixes: 5c492c3f5255 ("arm64: smp: Add function to determine if cpus are stuck in the kernel") > > Signed-off-by: Mark Salter <msalter@redhat.com> > > --- > > arch/arm64/kernel/smp.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > > index ef1caae..9b10365 100644 > > --- a/arch/arm64/kernel/smp.c > > +++ b/arch/arm64/kernel/smp.c > > @@ -944,7 +944,7 @@ static bool have_cpu_die(void) > > #ifdef CONFIG_HOTPLUG_CPU > > int any_cpu = raw_smp_processor_id(); > > > > - if (cpu_ops[any_cpu]->cpu_die) > > + if (cpu_ops[any_cpu] && cpu_ops[any_cpu]->cpu_die) > > return true; > > We take similar care in op_cpu_disable() and cpu_die_early(), so this is > certainly more in keeping with the rest of the arm64 code, and is an > improvement. > > ... however, I think there is a larger problem. Given cpu_ops can differ > by CPU, we could encounter a case where some CPUs had PSCI ops, and some > had none. In that case, have_cpu_die() can return different values on > different CPUs. > > ... which means that cpus_are_stuck_in_kernel() is on shaky ground, and > we may need a more comprehensive fix. > Hmm, cpus_are_stuck_in_kernel() is called from hibernate.c where there would be a problem if any cpu was stuck in kernel. It is also called from machine_kexec.c where there would be a problem if any but the calling cpu was stuck in kernel. So clearly something else is needed...
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index ef1caae..9b10365 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -944,7 +944,7 @@ static bool have_cpu_die(void) #ifdef CONFIG_HOTPLUG_CPU int any_cpu = raw_smp_processor_id(); - if (cpu_ops[any_cpu]->cpu_die) + if (cpu_ops[any_cpu] && cpu_ops[any_cpu]->cpu_die) return true; #endif return false;
Commit 5c492c3f5255 ("arm64: smp: Add function to determine if cpus are stuck in the kernel") added a helper function to determine if die() is supported in cpu_ops. This function assumes a cpu will have a valid cpu_ops entry, but that may not be the case for cpu0 is spin-table or parking protocol is used to boot secondary cpus. In that case, there is a NULL dereference if have_cpu_die() is called by cpu0. So add a check for a valid cpu_ops before dereferencing it. Fixes: 5c492c3f5255 ("arm64: smp: Add function to determine if cpus are stuck in the kernel") Signed-off-by: Mark Salter <msalter@redhat.com> --- arch/arm64/kernel/smp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)