From 732fd9f0b9c1cdc6dfd77162ded60df005182cc0 Mon Sep 17 00:00:00 2001 From: Cunlong Li Date: Thu, 28 May 2026 10:48:44 +0800 Subject: zram: fix use-after-free in zram_bvec_write_partial() zram_read_page() picks the sync or async backing device read path based on whether the parent bio is NULL. zram_bvec_write_partial() passes its parent bio down, so for ZRAM_WB slots the read is dispatched asynchronously and zram_read_page() returns 0 while the bio is still in flight. The caller then runs memcpy_from_bvec(), zram_write_page() and __free_page() on the buffer, leaving the async read to write into a freed page. zram_bvec_read_partial() was switched to NULL in commit 4e3c87b9421d ("zram: fix synchronous reads") for the same reason; the write_partial counterpart was missed. Link: https://lore.kernel.org/20260528-zram-v3-1-cab86eef8764@gmail.com Fixes: 8e654f8fbff5 ("zram: read page from backing device") Reviewed-by: Christoph Hellwig Reviewed-by: Sergey Senozhatsky Signed-off-by: Cunlong Li Cc: Jens Axboe Cc: Minchan Kim Cc: Yisheng Xie Cc: Signed-off-by: Andrew Morton --- drivers/block/zram/zram_drv.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers') diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 07111455eecf..e11ee1ed3832 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -2337,7 +2337,7 @@ static int zram_bvec_write_partial(struct zram *zram, struct bio_vec *bvec, if (!page) return -ENOMEM; - ret = zram_read_page(zram, page, index, bio); + ret = zram_read_page(zram, page, index, NULL); if (!ret) { memcpy_from_bvec(page_address(page) + offset, bvec); ret = zram_write_page(zram, page, index); -- cgit v1.2.3