mm: fix dereference a null pointer in migrate[_huge]_page_move_mapping()
stable inclusion from linux-4.19.236 commit deebce9df9ffaa62613bfcd8351d0c43a9a66108 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5646A CVE: NA -------------------------------- 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> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by:
Yongqiang Liu <liuyongqiang13@huawei.com>
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