From: Barry Song <v-songbaohua@xxxxxxxx>
sg_init_one() relies on linearly mapped low memory for the safe
utilization of virt_to_page(). Consequently, we have two choices:
either employ kmap_to_page() alongside sg_set_page(), or resort to
copying high memory contents to a temporary buffer residing in low
memory. However, considering the introduction of the WARN_ON_ONCE
in commit ef6e06b2ef870 ("highmem: fix kmap_to_page() for
kmap_local_page() addresses"), which specifically addresses high
memory concerns, it appears that memcpy remains the sole viable
option.
Reported-and-tested-by: syzbot+adbc983a1588b7805de3@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://lore.kernel.org/all/000000000000bbb3d80613f243a6@xxxxxxxxxx/
Fixes: 270700dd06ca ("mm/zswap: remove the memcpy if acomp is not sleepable")
Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
---
mm/zswap.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/mm/zswap.c b/mm/zswap.c
index 9dec853647c8..17bf6d87b274 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1080,7 +1080,8 @@ static void zswap_decompress(struct zswap_entry *entry, struct page *page)
mutex_lock(&acomp_ctx->mutex);
src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
- if (acomp_ctx->is_sleepable && !zpool_can_sleep_mapped(zpool)) {
+ if ((acomp_ctx->is_sleepable && !zpool_can_sleep_mapped(zpool)) ||
+ !virt_addr_valid(src)) {
memcpy(acomp_ctx->buffer, src, entry->length);
src = acomp_ctx->buffer;
zpool_unmap_handle(zpool, entry->handle);
@@ -1094,7 +1095,7 @@ static void zswap_decompress(struct zswap_entry *entry, struct page *page)
BUG_ON(acomp_ctx->req->dlen != PAGE_SIZE);
mutex_unlock(&acomp_ctx->mutex);
- if (!acomp_ctx->is_sleepable || zpool_can_sleep_mapped(zpool))
+ if (src != acomp_ctx->buffer)
zpool_unmap_handle(zpool, entry->handle);
}
--
2.34.1
