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b=CgZHKp3fFsHD6pZE97W2eHD0S/3+v5Jskr/Gt2dFx6r/HuEBeQMiDXtAjxQWCqXp4 cLwxQU3j9NQXW9pDWvSy8koH7wakDDu7qYjJRgKoVlB8esyac5o2s5Qy/byRZTJDyH 8zj5PYZDq+yROLWGS5JwiupukUpGrmt6rWYhMmss5MbzhuxwrYb4YqlO6xmHL8yy0u ZMauVv2gS/wowDY2H6lJUXx+uMf76vsUV9dCsxzN/2XocDAdmaIlq2XQU1jyOXzyOW 7oLI/s4Tn0cGNXGkAMqODU9/zcSlSF8i/XxDig3vKaHrGIaci6i1+TQj+O1XyHkNBW 7Og2PBwKLddRg== From: Christian Brauner Date: Mon, 21 Sep 2026 15:45:01 +0200 Subject: [PATCH v3 12/17] exec: cancel io_uring requests before de_thread() MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260921-work-coredump-fixes-v3-12-8e4adb1619e6@kernel.org> References: <20260921-work-coredump-fixes-v3-0-8e4adb1619e6@kernel.org> In-Reply-To: <20260921-work-coredump-fixes-v3-0-8e4adb1619e6@kernel.org> To: Oleg Nesterov , Chris Mason , linux-fsdevel@vger.kernel.org Cc: Jens Axboe , Alexander Viro , Jan Kara , NeilBrown , Ingo Molnar , Peter Zijlstra , linux-mm@kvack.org, io-uring@vger.kernel.org, "Christian Brauner (Amutable)" , stable@vger.kernel.org X-Mailer: b4 0.17-dev-db0b7 X-Developer-Signature: v=1; a=openpgp-sha256; l=2082; i=brauner@kernel.org; h=from:subject:message-id; bh=E2TTe46dbf8f5z7wtULy+9nnGSgHQ2lB5ZQgulfnziY=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWRtNLlTFOJ1IImRndEjO6tTMrTxl7/dfrfjKxhZvNn9+ I+xJ37tKGVhEONikBVTZHFoNwmXW85TsdkoUwNmDisTyBAGLk4BmEhiIyPDDMF5X7h1WBpmPs5M a7yy/qhty+TYX6K3bVenhD1XbZ8GVHFO1VFadPY/X8YfQVEL2nIkrD5emJcf7N3La+vy3ak1jx8 A X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 6A9741A000A X-Stat-Signature: nzw6sgswct4onw6c8efw9wprc85eukbu X-HE-Tag: 1789998350-480246 X-HE-Meta: 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 6AAdANmu YzRg52UoscHHy5ZmrjJ6GOgmaXqhc5VXhOJ8GFk2BFnA8O/Q+7gwXXSoGBV1EJzvPNWjTpxUh3sGlWfgjrKHsoYuO95nhJ66RCcSxP1MhP9oFatEjGd2GGXCoUANlyOdvZwpZ2ERM29W4sB+i96IWC+GFDfzQPsvRbGMZjCcR/DxxElMoe5Ap/7ybXnEB6LSrcle4JtFISZQ4solNGw0siQfHslYxgipqGqcx710sQXLqLqzPsnvZY+VVUIxd979JESfT1jSWsfuLvOFrU2lczzTHAgrh9UVCrkCrIWEIRxSjMoh/j99PXzgMvou26+IwT69lF4da0kls+NWFFfWXa888wQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: begin_new_exec() cancels the exec'ing thread's io_uring requests after de_thread() made it the only thread in the thread-group. Now io_uring_task_cancel() runs task work after. If it runs a create_worker_cb() item then a io-wq queued on the thread before the exec creates a new io-wq worker thread. Said thread joins the thread-group which de_thread() just took down. The io-iwq sticks around until it notices that its workqueue is dying. But code after de_thread() relies on being single-threaded. Move io_uring_task_cancel() before de_thread() but behind the point of no return. Any worker created during task work run from io_uring_task_cancel() is just a sibling thread that de_thread() will take down and reap. Once io_uring_task_cancel() returned the thread has neither a task context nor a workqueue left so nothing can add a thread behind de_thread()'s back anymore. Suggested-by: Oleg Nesterov Link: https://lore.kernel.org/r/aq0_lvHDViIpX_Mu@redhat.com Fixes: 3bfe6106693b ("io-wq: fork worker threads from original task") Cc: stable@vger.kernel.org Signed-off-by: Christian Brauner (Amutable) --- fs/exec.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 075a744421e1..334e6d358c56 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1149,16 +1149,19 @@ int begin_new_exec(struct linux_binprm * bprm) */ bprm->point_of_no_return = true; + /* + * Cancel any io_uring activity across execve. This runs task work + * that may still create an io-wq worker, so do it while de_thread() + * can still zap it. + */ + io_uring_task_cancel(); + /* Make this the only thread in the thread group */ retval = de_thread(me); if (retval) goto out; /* see the comment in check_unsafe_exec() */ current->fs->in_exec = 0; - /* - * Cancel any io_uring activity across execve - */ - io_uring_task_cancel(); /* Ensure the files table is not shared. */ retval = unshare_fd(CLONE_FILES, &files); -- 2.53.0