| Message ID | 20220217115416.55835-1-liqiong@nfschina.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [4.19,STABLE] mm: fix dereference a null pointer in migrate[_huge]_page_move_mapping() | expand |
On Thu, Feb 17, 2022 at 07:54:16PM +0800, liqiong wrote: > Upstream doesn't use radix tree any more in migrate.c, no need this patch. > > The two functions look up a slot and dereference the pointer, > If the pointer is null, the kernel would crash and dump. > > The 'numad' service calls 'migrate_pages' periodically. If some slots > being replaced (Cache Eviction), the radix_tree_lookup_slot() returns > a null pointer that causes kernel crash. > > "numad": crash> bt > [exception RIP: migrate_page_move_mapping+337] > > Introduce pointer checking to avoid dereference a null pointer. > > Cc: <stable@vger.kernel.org> # linux-4.19.y > Signed-off-by: liqiong <liqiong@nfschina.com> > --- > mm/migrate.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/mm/migrate.c b/mm/migrate.c > index a69b842f95da..76f8dedc0e02 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -472,6 +472,10 @@ int migrate_page_move_mapping(struct address_space *mapping, > > pslot = radix_tree_lookup_slot(&mapping->i_pages, > page_index(page)); > + if (pslot == NULL) { > + xa_unlock_irq(&mapping->i_pages); > + return -EAGAIN; > + } > > expected_count += hpage_nr_pages(page) + page_has_private(page); > if (page_count(page) != expected_count || > @@ -590,6 +594,10 @@ int migrate_huge_page_move_mapping(struct address_space *mapping, > xa_lock_irq(&mapping->i_pages); > > pslot = radix_tree_lookup_slot(&mapping->i_pages, page_index(page)); > + if (pslot == NULL) { > + xa_unlock_irq(&mapping->i_pages); > + return -EAGAIN; > + } > > expected_count = 2 + page_has_private(page); > if (page_count(page) != expected_count || > -- > 2.25.1 > Sorry for the delay, now queued up. greg k-h
diff --git a/mm/migrate.c b/mm/migrate.c index a69b842f95da..76f8dedc0e02 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -472,6 +472,10 @@ int migrate_page_move_mapping(struct address_space *mapping, pslot = radix_tree_lookup_slot(&mapping->i_pages, page_index(page)); + if (pslot == NULL) { + xa_unlock_irq(&mapping->i_pages); + return -EAGAIN; + } expected_count += hpage_nr_pages(page) + page_has_private(page); if (page_count(page) != expected_count || @@ -590,6 +594,10 @@ int migrate_huge_page_move_mapping(struct address_space *mapping, xa_lock_irq(&mapping->i_pages); pslot = radix_tree_lookup_slot(&mapping->i_pages, page_index(page)); + if (pslot == NULL) { + xa_unlock_irq(&mapping->i_pages); + return -EAGAIN; + } expected_count = 2 + page_has_private(page); if (page_count(page) != expected_count ||
Upstream doesn't use radix tree any more in migrate.c, no need this patch. The two functions look up a slot and dereference the pointer, If the pointer is null, the kernel would crash and dump. The 'numad' service calls 'migrate_pages' periodically. If some slots being replaced (Cache Eviction), the radix_tree_lookup_slot() returns a null pointer that causes kernel crash. "numad": crash> bt [exception RIP: migrate_page_move_mapping+337] Introduce pointer checking to avoid dereference a null pointer. Cc: <stable@vger.kernel.org> # linux-4.19.y Signed-off-by: liqiong <liqiong@nfschina.com> --- mm/migrate.c | 8 ++++++++ 1 file changed, 8 insertions(+)