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Tue, 26 May 2026 20:45:41 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:b55c:5b57:6435:9af4]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2beb58b2ccbsm141659055ad.48.2026.05.26.20.45.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 May 2026 20:45:40 -0700 (PDT) Date: Wed, 27 May 2026 12:45:37 +0900 From: Sergey Senozhatsky To: Cunlong Li Cc: Minchan Kim , Sergey Senozhatsky , Jens Axboe , Andrew Morton , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, Christoph Hellwig , stable@vger.kernel.org Subject: Re: [PATCH] zram: fix use-after-free in zram_bvec_write_partial() Message-ID: References: <20260527-zram-v1-1-ce1acb2bfaf9@gmail.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260527-zram-v1-1-ce1acb2bfaf9@gmail.com> On (26/05/27 11:26), Cunlong Li wrote: > 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. > > Fixes: 4e3c87b9421d ("zram: fix synchronous reads") > Cc: Christoph Hellwig > Cc: stable@vger.kernel.org > Signed-off-by: Cunlong Li > --- > drivers/block/zram/zram_drv.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c > index aebc710f0d6a..b23a8bbb687c 100644 > --- a/drivers/block/zram/zram_drv.c > +++ b/drivers/block/zram/zram_drv.c > @@ -2333,7 +2333,7 @@ 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); Sounds like zram_bvec_write_partial() doesn't need bio parameter then?