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Thu, 15 Apr 2021 10:43:37 -0700 (PDT) Subject: Re: [PATCH] block: reexpand iov_iter after read/write From: Pavel Begunkov To: yangerkun , axboe@kernel.dk Cc: viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, io-uring@vger.kernel.org References: <20210401071807.3328235-1-yangerkun@huawei.com> <7ff7d1b7-8b6d-a684-1740-6a62565f77b6@gmail.com> Autocrypt: addr=asml.silence@gmail.com; prefer-encrypt=mutual; keydata= mQINBFmKBOQBEAC76ZFxLAKpDw0bKQ8CEiYJRGn8MHTUhURL02/7n1t0HkKQx2K1fCXClbps bdwSHrhOWdW61pmfMbDYbTj6ZvGRvhoLWfGkzujB2wjNcbNTXIoOzJEGISHaPf6E2IQx1ik9 6uqVkK1OMb7qRvKH0i7HYP4WJzYbEWVyLiAxUj611mC9tgd73oqZ2pLYzGTqF2j6a/obaqha +hXuWTvpDQXqcOZJXIW43atprH03G1tQs7VwR21Q1eq6Yvy2ESLdc38EqCszBfQRMmKy+cfp W3U9Mb1w0L680pXrONcnlDBCN7/sghGeMHjGKfNANjPc+0hzz3rApPxpoE7HC1uRiwC4et83 CKnncH1l7zgeBT9Oa3qEiBlaa1ZCBqrA4dY+z5fWJYjMpwI1SNp37RtF8fKXbKQg+JuUjAa9 Y6oXeyEvDHMyJYMcinl6xCqCBAXPHnHmawkMMgjr3BBRzODmMr+CPVvnYe7BFYfoajzqzq+h EyXSl3aBf0IDPTqSUrhbmjj5OEOYgRW5p+mdYtY1cXeK8copmd+fd/eTkghok5li58AojCba jRjp7zVOLOjDlpxxiKhuFmpV4yWNh5JJaTbwCRSd04sCcDNlJj+TehTr+o1QiORzc2t+N5iJ NbILft19Izdn8U39T5oWiynqa1qCLgbuFtnYx1HlUq/HvAm+kwARAQABtDFQYXZlbCBCZWd1 bmtvdiAoc2lsZW5jZSkgPGFzbWwuc2lsZW5jZUBnbWFpbC5jb20+iQJOBBMBCAA4FiEE+6Ju PTjTbx479o3OWt5b1Glr+6UFAlmKBOQCGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQ Wt5b1Glr+6WxZA//QueaKHzgdnOikJ7NA/Vq8FmhRlwgtP0+E+w93kL+ZGLzS/cUCIjn2f4Q Mcutj2Neg0CcYPX3b2nJiKr5Vn0rjJ/suiaOa1h1KzyNTOmxnsqE5fmxOf6C6x+NKE18I5Jy xzLQoktbdDVA7JfB1itt6iWSNoOTVcvFyvfe5ggy6FSCcP+m1RlR58XxVLH+qlAvxxOeEr/e aQfUzrs7gqdSd9zQGEZo0jtuBiB7k98t9y0oC9Jz0PJdvaj1NZUgtXG9pEtww3LdeXP/TkFl HBSxVflzeoFaj4UAuy8+uve7ya/ECNCc8kk0VYaEjoVrzJcYdKP583iRhOLlZA6HEmn/+Gh9 4orG67HNiJlbFiW3whxGizWsrtFNLsSP1YrEReYk9j1SoUHHzsu+ZtNfKuHIhK0sU07G1OPN 2rDLlzUWR9Jc22INAkhVHOogOcc5ajMGhgWcBJMLCoi219HlX69LIDu3Y34uIg9QPZIC2jwr 24W0kxmK6avJr7+n4o8m6sOJvhlumSp5TSNhRiKvAHB1I2JB8Q1yZCIPzx+w1ALxuoWiCdwV M/azguU42R17IuBzK0S3hPjXpEi2sK/k4pEPnHVUv9Cu09HCNnd6BRfFGjo8M9kZvw360gC1 reeMdqGjwQ68o9x0R7NBRrtUOh48TDLXCANAg97wjPoy37dQE7e5Ag0EWYoE5AEQAMWS+aBV IJtCjwtfCOV98NamFpDEjBMrCAfLm7wZlmXy5I6o7nzzCxEw06P2rhzp1hIqkaab1kHySU7g dkpjmQ7Jjlrf6KdMP87mC/Hx4+zgVCkTQCKkIxNE76Ff3O9uTvkWCspSh9J0qPYyCaVta2D1 Sq5HZ8WFcap71iVO1f2/FEHKJNz/YTSOS/W7dxJdXl2eoj3gYX2UZNfoaVv8OXKaWslZlgqN jSg9wsTv1K73AnQKt4fFhscN9YFxhtgD/SQuOldE5Ws4UlJoaFX/yCoJL3ky2kC0WFngzwRF Yo6u/KON/o28yyP+alYRMBrN0Dm60FuVSIFafSqXoJTIjSZ6olbEoT0u17Rag8BxnxryMrgR dkccq272MaSS0eOC9K2rtvxzddohRFPcy/8bkX+t2iukTDz75KSTKO+chce62Xxdg62dpkZX xK+HeDCZ7gRNZvAbDETr6XI63hPKi891GeZqvqQVYR8e+V2725w+H1iv3THiB1tx4L2bXZDI DtMKQ5D2RvCHNdPNcZeldEoJwKoA60yg6tuUquvsLvfCwtrmVI2rL2djYxRfGNmFMrUDN1Xq F3xozA91q3iZd9OYi9G+M/OA01husBdcIzj1hu0aL+MGg4Gqk6XwjoSxVd4YT41kTU7Kk+/I 5/Nf+i88ULt6HanBYcY/+Daeo/XFABEBAAGJAjYEGAEIACAWIQT7om49ONNvHjv2jc5a3lvU aWv7pQUCWYoE5AIbDAAKCRBa3lvUaWv7pfmcEACKTRQ28b1y5ztKuLdLr79+T+LwZKHjX++P 4wKjEOECCcB6KCv3hP+J2GCXDOPZvdg/ZYZafqP68Yy8AZqkfa4qPYHmIdpODtRzZSL48kM8 LRzV8Rl7J3ItvzdBRxf4T/Zseu5U6ELiQdCUkPGsJcPIJkgPjO2ROG/ZtYa9DvnShNWPlp+R uPwPccEQPWO/NP4fJl2zwC6byjljZhW5kxYswGMLBwb5cDUZAisIukyAa8Xshdan6C2RZcNs rB3L7vsg/R8UCehxOH0C+NypG2GqjVejNZsc7bgV49EOVltS+GmGyY+moIzxsuLmT93rqyII 5rSbbcTLe6KBYcs24XEoo49Zm9oDA3jYvNpeYD8rDcnNbuZh9kTgBwFN41JHOPv0W2FEEWqe JsCwQdcOQ56rtezdCJUYmRAt3BsfjN3Jn3N6rpodi4Dkdli8HylM5iq4ooeb5VkQ7UZxbCWt UVMKkOCdFhutRmYp0mbv2e87IK4erwNHQRkHUkzbsuym8RVpAZbLzLPIYK/J3RTErL6Z99N2 m3J6pjwSJY/zNwuFPs9zGEnRO4g0BUbwGdbuvDzaq6/3OJLKohr5eLXNU3JkT+3HezydWm3W OPhauth7W0db74Qd49HXK0xe/aPrK+Cp+kU1HRactyNtF8jZQbhMCC8vMGukZtWaAwpjWiiH bA== Message-ID: <3368729f-e61d-d4b6-f2ae-e17ebe59280e@gmail.com> Date: Thu, 15 Apr 2021 18:39:28 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <7ff7d1b7-8b6d-a684-1740-6a62565f77b6@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 15/04/2021 18:37, Pavel Begunkov wrote: > On 09/04/2021 15:49, Pavel Begunkov wrote: >> On 01/04/2021 08:18, yangerkun wrote: >>> We get a bug: >>> >>> BUG: KASAN: slab-out-of-bounds in iov_iter_revert+0x11c/0x404 >>> lib/iov_iter.c:1139 >>> Read of size 8 at addr ffff0000d3fb11f8 by task >>> >>> CPU: 0 PID: 12582 Comm: syz-executor.2 Not tainted >>> 5.10.0-00843-g352c8610ccd2 #2 >>> Hardware name: linux,dummy-virt (DT) >>> Call trace: > ... >>> __asan_load8+0xb4/0xbc mm/kasan/generic.c:252 >>> iov_iter_revert+0x11c/0x404 lib/iov_iter.c:1139 >>> io_read fs/io_uring.c:3421 [inline] >>> io_issue_sqe+0x2344/0x2d64 fs/io_uring.c:5943 >>> __io_queue_sqe+0x19c/0x520 fs/io_uring.c:6260 >>> io_queue_sqe+0x2a4/0x590 fs/io_uring.c:6326 >>> io_submit_sqe fs/io_uring.c:6395 [inline] >>> io_submit_sqes+0x4c0/0xa04 fs/io_uring.c:6624 > ... >>> >>> blkdev_read_iter can truncate iov_iter's count since the count + pos may >>> exceed the size of the blkdev. This will confuse io_read that we have >>> consume the iovec. And once we do the iov_iter_revert in io_read, we >>> will trigger the slab-out-of-bounds. Fix it by reexpand the count with >>> size has been truncated. >> >> Looks right, >> >> Acked-by: Pavel Begunkov > > Fwiw, we need to forget to drag it through 5.13 + stable Err, yypo, to _not_ forget to 5.13 + stable... > > >>> >>> blkdev_write_iter can trigger the problem too. >>> >>> Signed-off-by: yangerkun >>> --- >>> fs/block_dev.c | 20 +++++++++++++++++--- >>> 1 file changed, 17 insertions(+), 3 deletions(-) >>> >>> diff --git a/fs/block_dev.c b/fs/block_dev.c >>> index 92ed7d5df677..788e1014576f 100644 >>> --- a/fs/block_dev.c >>> +++ b/fs/block_dev.c >>> @@ -1680,6 +1680,7 @@ ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from) >>> struct inode *bd_inode = bdev_file_inode(file); >>> loff_t size = i_size_read(bd_inode); >>> struct blk_plug plug; >>> + size_t shorted = 0; >>> ssize_t ret; >>> >>> if (bdev_read_only(I_BDEV(bd_inode))) >>> @@ -1697,12 +1698,17 @@ ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from) >>> if ((iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT)) == IOCB_NOWAIT) >>> return -EOPNOTSUPP; >>> >>> - iov_iter_truncate(from, size - iocb->ki_pos); >>> + size -= iocb->ki_pos; >>> + if (iov_iter_count(from) > size) { >>> + shorted = iov_iter_count(from) - size; >>> + iov_iter_truncate(from, size); >>> + } >>> >>> blk_start_plug(&plug); >>> ret = __generic_file_write_iter(iocb, from); >>> if (ret > 0) >>> ret = generic_write_sync(iocb, ret); >>> + iov_iter_reexpand(from, iov_iter_count(from) + shorted); >>> blk_finish_plug(&plug); >>> return ret; >>> } >>> @@ -1714,13 +1720,21 @@ ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to) >>> struct inode *bd_inode = bdev_file_inode(file); >>> loff_t size = i_size_read(bd_inode); >>> loff_t pos = iocb->ki_pos; >>> + size_t shorted = 0; >>> + ssize_t ret; >>> >>> if (pos >= size) >>> return 0; >>> >>> size -= pos; >>> - iov_iter_truncate(to, size); >>> - return generic_file_read_iter(iocb, to); >>> + if (iov_iter_count(to) > size) { >>> + shorted = iov_iter_count(to) - size; >>> + iov_iter_truncate(to, size); >>> + } >>> + >>> + ret = generic_file_read_iter(iocb, to); >>> + iov_iter_reexpand(to, iov_iter_count(to) + shorted); >>> + return ret; >>> } >>> EXPORT_SYMBOL_GPL(blkdev_read_iter); >>> >>> >> > -- Pavel Begunkov