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Tue, 26 May 2026 21:49:31 -0700 (PDT) From: Cunlong Li Date: Wed, 27 May 2026 12:49:24 +0800 Subject: [PATCH v2 1/2] zram: fix use-after-free in zram_bvec_write_partial() Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260527-zram-v2-1-2fb84b054b5c@gmail.com> References: <20260527-zram-v2-0-2fb84b054b5c@gmail.com> In-Reply-To: <20260527-zram-v2-0-2fb84b054b5c@gmail.com> To: Minchan Kim , Sergey Senozhatsky , Jens Axboe , Andrew Morton Cc: Christoph Hellwig , linux-block@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Cunlong Li , stable@vger.kernel.org X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1779857366; l=1429; i=shenxiaogll@gmail.com; s=20260517; h=from:subject:message-id; bh=GYq7eClao3GaV9lgjcsADvNLW1hhn25v8rqXYSyuj3E=; b=y0NCB/JE8egqDA7ZvcgiKHXXTPhJDt3eJNcyH9vjqfcf2urXXxuO/7LuiX3+8OQB5bskhQHGQ e9j1YvGYcbyBEJhvACdZy6pB4TiDjVceAUvbcQ9UF8MJErpnJDy5PYO X-Developer-Key: i=shenxiaogll@gmail.com; a=ed25519; pk=SKFifnqPdsvsjuhUiq+Y9vtCdhyZ/LrRcfYn8eRq6AE= 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 Reviewed-by: Christoph Hellwig Reviewed-by: Sergey Senozhatsky --- 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; =20 - ret =3D zram_read_page(zram, page, index, bio); + ret =3D zram_read_page(zram, page, index, NULL); if (!ret) { memcpy_from_bvec(page_address(page) + offset, bvec); ret =3D zram_write_page(zram, page, index); --=20 2.30.2 From nobody Mon Jun 8 19:36:09 2026 Received: from mail-pl1-f170.google.com (mail-pl1-f170.google.com [209.85.214.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D93BB2E0B71 for ; 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Tue, 26 May 2026 21:49:35 -0700 (PDT) Received: from [127.0.0.1] ([116.80.91.208]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2beb58dba7bsm135704105ad.66.2026.05.26.21.49.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 May 2026 21:49:34 -0700 (PDT) From: Cunlong Li Date: Wed, 27 May 2026 12:49:25 +0800 Subject: [PATCH v2 2/2] zram: drop unused bio parameter from write helpers Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260527-zram-v2-2-2fb84b054b5c@gmail.com> References: <20260527-zram-v2-0-2fb84b054b5c@gmail.com> In-Reply-To: <20260527-zram-v2-0-2fb84b054b5c@gmail.com> To: Minchan Kim , Sergey Senozhatsky , Jens Axboe , Andrew Morton Cc: Christoph Hellwig , linux-block@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Cunlong Li X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1779857366; l=1967; i=shenxiaogll@gmail.com; s=20260517; h=from:subject:message-id; bh=wWeEghQAe5NXkXvNqKfo8YuljpN08ui3FSM1U5zjH2s=; b=p1wzwgJ3gwvvVn04ePPF6uh4LDB/aFn6+9vSP6I90FUu4ui1uDqy8TlmNZy2nWAdU2iw4W1Ky Jfp1gcsQY9vA3sSfO0yTYLUEuIiWUpg0W6toLaFhTRFvUW+rMPu1R3x X-Developer-Key: i=shenxiaogll@gmail.com; a=ed25519; pk=SKFifnqPdsvsjuhUiq+Y9vtCdhyZ/LrRcfYn8eRq6AE= After the previous fix, zram_bvec_write_partial() always passes NULL to zram_read_page() and no longer needs the parent bio. Mirror the read side (zram_bvec_read_partial() has not taken a bio since commit 4e3c87b9421d ("zram: fix synchronous reads")) and drop the parameter from zram_bvec_write_partial() and zram_bvec_write(). No functional change. Signed-off-by: Cunlong Li Reviewed-by: Christoph Hellwig Reviewed-by: Sergey Senozhatsky --- drivers/block/zram/zram_drv.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index b23a8bbb687c..66347915a2cc 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -2325,7 +2325,7 @@ static int zram_write_page(struct zram *zram, struct = page *page, u32 index) * This is a partial IO. Read the full page before writing the changes. */ static int zram_bvec_write_partial(struct zram *zram, struct bio_vec *bvec, - u32 index, int offset, struct bio *bio) + u32 index, int offset) { struct page *page =3D alloc_page(GFP_NOIO); int ret; @@ -2343,10 +2343,10 @@ static int zram_bvec_write_partial(struct zram *zra= m, struct bio_vec *bvec, } =20 static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, - u32 index, int offset, struct bio *bio) + u32 index, int offset) { if (is_partial_io(bvec)) - return zram_bvec_write_partial(zram, bvec, index, offset, bio); + return zram_bvec_write_partial(zram, bvec, index, offset); return zram_write_page(zram, bvec->bv_page, index); } =20 @@ -2743,7 +2743,7 @@ static void zram_bio_write(struct zram *zram, struct = bio *bio) =20 bv.bv_len =3D min_t(u32, bv.bv_len, PAGE_SIZE - offset); =20 - if (zram_bvec_write(zram, &bv, index, offset, bio) < 0) { + if (zram_bvec_write(zram, &bv, index, offset) < 0) { atomic64_inc(&zram->stats.failed_writes); bio->bi_status =3D BLK_STS_IOERR; break; --=20 2.30.2