| Message ID | 1559121387-674-3-git-send-email-anshuman.khandual@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64/mm: Enable memory hot remove | expand |
On Wed, May 29, 2019 at 02:46:26PM +0530, Anshuman Khandual wrote: > The arm64 page table dump code can race with concurrent modification of the > kernel page tables. When a leaf entries are modified concurrently, the dump > code may log stale or inconsistent information for a VA range, but this is > otherwise not harmful. > > When intermediate levels of table are freed, the dump code will continue to > use memory which has been freed and potentially reallocated for another > purpose. In such cases, the dump code may dereference bogus addresses, > leading to a number of potential problems. > > Intermediate levels of table may by freed during memory hot-remove, > which will be enabled by a subsequent patch. To avoid racing with > this, take the memory hotplug lock when walking the kernel page table. > > Acked-by: David Hildenbrand <david@redhat.com> > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- > arch/arm64/mm/ptdump_debugfs.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c > index 064163f..80171d1 100644 > --- a/arch/arm64/mm/ptdump_debugfs.c > +++ b/arch/arm64/mm/ptdump_debugfs.c > @@ -7,7 +7,10 @@ > static int ptdump_show(struct seq_file *m, void *v) > { > struct ptdump_info *info = m->private; > + > + get_online_mems(); > ptdump_walk_pgd(m, info); > + put_online_mems(); We need to explicitly include <linux/memory_hotplug.h> to get the prototypes of {get,put}_online_mems(). With that fixed up: Acked-by: Mark Rutland <mark.rutland@arm.com> I understand from [1] that Michal is ok with using these here, and we're open to reworking this if/when the hotplug locking is changed. Mark. [1] https://lkml.kernel.org/r/20190527072001.GB1658@dhcp22.suse.cz > return 0; > } > DEFINE_SHOW_ATTRIBUTE(ptdump); > -- > 2.7.4 >
diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c index 064163f..80171d1 100644 --- a/arch/arm64/mm/ptdump_debugfs.c +++ b/arch/arm64/mm/ptdump_debugfs.c @@ -7,7 +7,10 @@ static int ptdump_show(struct seq_file *m, void *v) { struct ptdump_info *info = m->private; + + get_online_mems(); ptdump_walk_pgd(m, info); + put_online_mems(); return 0; } DEFINE_SHOW_ATTRIBUTE(ptdump);