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[50.113.46.110]) by smtp.gmail.com with ESMTPSA id l14sm224203pjz.32.2022.02.23.11.13.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 23 Feb 2022 11:13:36 -0800 (PST) Message-ID: <3c7903dd-fc50-3b05-8419-0f5011c5e82c@linaro.org> Date: Wed, 23 Feb 2022 09:13:33 -1000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: Fix a potential Use-after-free bug in handle_simd_shift_fpint_conv() (v6.2.0). Content-Language: en-US To: wliang@stu.xidian.edu.cn, qemu-devel@nongnu.org, Peter Maydell References: <5ec4ffe1.25b2.17f27005362.Coremail.wliang@stu.xidian.edu.cn> From: Richard Henderson In-Reply-To: <5ec4ffe1.25b2.17f27005362.Coremail.wliang@stu.xidian.edu.cn> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Host-Lookup-Failed: Reverse DNS lookup failed for 2607:f8b0:4864:20::62a (failed) Received-SPF: pass client-ip=2607:f8b0:4864:20::62a; envelope-from=richard.henderson@linaro.org; helo=mail-pl1-x62a.google.com X-Spam_score_int: -6 X-Spam_score: -0.7 X-Spam_bar: / X-Spam_report: (-0.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, PDS_HP_HELO_NORDNS=0.659, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2/23/22 04:33, wliang@stu.xidian.edu.cn wrote: > > Hi all, > > I find a potential Use-after-free bug in QEMU 6.2.0, which is in > handle_simd_shift_fpint_conv()(./target/arm/translate-a64.c). > > At line 9048, a variable 'tcg_fpstatus' is freed by invoking tcg_temp_free_ptr(). However, > at line 9050, the variable 'tcg_fpstatus' is subsequently use as the 3rd parameter of the > function gen_helper_set_rmode. This may result in a use-after-free bug. > > > 9048    tcg_temp_free_ptr(tcg_fpstatus); > 9049    tcg_temp_free_i32(tcg_shift); > 9050    gen_helper_set_rmode(tcg_rmode, tcg_rmode, tcg_fpstatus); > > > I believe the bug can be fixed by invoking the gen_helper_set_rmode() before > 'tcg_fpstatus' being freed by the tcg_temp_free_ptr(). > > >  ---    tcg_temp_free_ptr(tcg_fpstatus); > 9049    tcg_temp_free_i32(tcg_shift); > 9050    gen_helper_set_rmode(tcg_rmode, tcg_rmode, tcg_fpstatus); >  +++    tcg_temp_free_ptr(tcg_fpstatus); > > I'm looking forward to your confirmation. The fix is correct. We just need the submission formatted properly, with your Signed-off-by tag. When re-formatting, you can add my Reviewed-by: Richard Henderson r~