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| author | liqiong <liqiong@nfschina.com> | 2022-02-17 19:54:16 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-03-23 09:10:42 +0100 |
| commit | deebce9df9ffaa62613bfcd8351d0c43a9a66108 (patch) | |
| tree | 8209b5f8691abb311ba5d1ce623e74abed480cb0 | |
| parent | aa44002e7db25f333ddf412fb81e8db6c100841a (diff) | |
| download | linux-stable-deebce9df9ffaa62613bfcd8351d0c43a9a66108.tar.gz linux-stable-deebce9df9ffaa62613bfcd8351d0c43a9a66108.tar.bz2 linux-stable-deebce9df9ffaa62613bfcd8351d0c43a9a66108.zip | |
mm: fix dereference a null pointer in migrate[_huge]_page_move_mapping()
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>
| -rw-r--r-- | mm/migrate.c | 8 |
1 files changed, 8 insertions, 0 deletions
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 || |