diff options
| author | Domenico Cerasuolo <cerasuolodomenico@gmail.com> | 2023-09-22 19:22:11 +0200 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-09-29 17:20:47 -0700 |
| commit | ca56489c2f1df516801eeff06129d2e9e282ab7b (patch) | |
| tree | f0552b6e6a11e149523eb7340e40c60525f175e8 /mm/zswap.c | |
| parent | 6f1bace9a9fb11402520ba7defa76bfaf7b8e09f (diff) | |
mm: zswap: fix potential memory corruption on duplicate store
While stress-testing zswap a memory corruption was happening when writing
back pages. __frontswap_store used to check for duplicate entries before
attempting to store a page in zswap, this was because if the store fails
the old entry isn't removed from the tree. This change removes duplicate
entries in zswap_store before the actual attempt.
[cerasuolodomenico@gmail.com: add a warning and a comment, per Johannes]
Link: https://lkml.kernel.org/r/20230925130002.1929369-1-cerasuolodomenico@gmail.com
Link: https://lkml.kernel.org/r/20230922172211.1704917-1-cerasuolodomenico@gmail.com
Fixes: 42c06a0e8ebe ("mm: kill frontswap")
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/zswap.c')
| -rw-r--r-- | mm/zswap.c | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/mm/zswap.c b/mm/zswap.c index 412b1409a0d7..083c693602b8 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -1219,6 +1219,19 @@ bool zswap_store(struct folio *folio) return false; /* + * If this is a duplicate, it must be removed before attempting to store + * it, otherwise, if the store fails the old page won't be removed from + * the tree, and it might be written back overriding the new data. + */ + spin_lock(&tree->lock); + dupentry = zswap_rb_search(&tree->rbroot, offset); + if (dupentry) { + zswap_duplicate_entry++; + zswap_invalidate_entry(tree, dupentry); + } + spin_unlock(&tree->lock); + + /* * XXX: zswap reclaim does not work with cgroups yet. Without a * cgroup-aware entry LRU, we will push out entries system-wide based on * local cgroup limits. @@ -1333,7 +1346,14 @@ insert_entry: /* map */ spin_lock(&tree->lock); + /* + * A duplicate entry should have been removed at the beginning of this + * function. Since the swap entry should be pinned, if a duplicate is + * found again here it means that something went wrong in the swap + * cache. + */ while (zswap_rb_insert(&tree->rbroot, entry, &dupentry) == -EEXIST) { + WARN_ON(1); zswap_duplicate_entry++; zswap_invalidate_entry(tree, dupentry); } |