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[46.193.73.98]) by smtp.gmail.com with ESMTPSA id t1-20020adfe101000000b0020d110bc39esm11037444wrz.64.2022.05.31.01.56.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 31 May 2022 01:56:47 -0700 (PDT) Message-ID: <1c5f149c-f7d0-e8be-d236-f0089d36ca60@kernel.dk> Date: Tue, 31 May 2022 02:56:46 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Subject: Re: [syzbot] UBSAN: array-index-out-of-bounds in io_submit_sqes Content-Language: en-US To: Dmitry Vyukov Cc: syzbot , asml.silence@gmail.com, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com References: <000000000000f0b26205e04a183b@google.com> <3d3c6b5f-84cd-cb25-812e-dac77e02ddbf@kernel.dk> From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 5/31/22 2:52 AM, Dmitry Vyukov wrote: > On Tue, 31 May 2022 at 10:45, Jens Axboe wrote: >> >> On 5/31/22 1:55 AM, syzbot wrote: >>> Hello, >>> >>> syzbot found the following issue on: >>> >>> HEAD commit: 3b46e4e44180 Add linux-next specific files for 20220531 >>> git tree: linux-next >>> console output: https://syzkaller.appspot.com/x/log.txt?x=16e151f5f00000 >>> kernel config: https://syzkaller.appspot.com/x/.config?x=ccb8d66fc9489ef >>> dashboard link: https://syzkaller.appspot.com/bug?extid=b6c9b65b6753d333d833 >>> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 >>> >>> Unfortunately, I don't have any reproducer for this issue yet. >>> >>> IMPORTANT: if you fix the issue, please add the following tag to the commit: >>> Reported-by: syzbot+b6c9b65b6753d333d833@syzkaller.appspotmail.com >>> >>> ================================================================================ >>> ================================================================================ >>> UBSAN: array-index-out-of-bounds in fs/io_uring.c:8860:19 >>> index 75 is out of range for type 'io_op_def [47]' >> >> 'def' is just set here, it's not actually used after 'opcode' has been >> verified. > > An interesting thing about C is that now the compiler is within its > rights to actually remove the check that is supposed to validate the > index because indexing io_op_defs[opcode] implies that opcode is > already within bounds, otherwise the program already has undefined > behavior, so removing the check is that case is also OK ;) I did fix this up as I think it's just a bug waiting to happen anyway. -- Jens Axboe