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[2401:d002:dc0f:2100:1047:c02f:591b:6a5c]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2a88b3eecc5sm166466385ad.17.2026.02.02.18.42.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 02 Feb 2026 18:42:13 -0800 (PST) Message-ID: Date: Tue, 3 Feb 2026 12:42:09 +1000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] linux-user/syscall.c: Prevent acquiring clone_lock while fork() To: Aleksandr Sergeev , qemu-devel@nongnu.org References: <20260126151612.2176451-1-sergeev0xef@gmail.com> From: Richard Henderson Content-Language: en-US In-Reply-To: <20260126151612.2176451-1-sergeev0xef@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::543; envelope-from=richard.henderson@linaro.org; helo=mail-pg1-x543.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development 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-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 1/27/26 01:16, Aleksandr Sergeev wrote: > By the spec, fork() copies only the thread which executes it. > So it may happen, what while one thread is doing a fork, > another thread is holding `clone_lock` mutex > (e.g. doing a `fork()` or `exit()`). > So the child process is born with the mutex being held, > and there are nobody to release it. > > As the thread executing do_syscall() is not considered running, > start_exclusive() does not protect us from the case. > > Resolves:https://gitlab.com/qemu-project/qemu/-/issues/3226 > Signed-off-by: Aleksandr Sergeev > --- > linux-user/main.c | 2 ++ > linux-user/syscall.c | 14 ++++++++++++++ > linux-user/user-internals.h | 2 ++ > 3 files changed, 18 insertions(+) Reviewed-by: Richard Henderson r~