From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 393F24AC15D; Thu, 17 Sep 2026 09:18:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789636688; cv=none; b=ItpasluMZoc5YAukQPDyq3BTMZxSAKbwDcxP8gehRyIBX/js9rwZjwNDOBzcrAbRZKDZurkdAzT39qJO/+3OgLa/nozXOSWpwEULxmWmks4qhxbvn9hIJ3Vofz1pP+fAb0sbZgYJX2MFkgmiN4zap0ijKEg8tFi3mifkKS7du3A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789636688; c=relaxed/simple; bh=QFgjXXUybA8CBQDzo0leFmaEK+XgKvIPes+QPTJhl4U=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=t3aJr90a+G+Idhcc5NomJvM6Jj6B0XQRK6OFSFPx/+YHz7nHiL7x0KQAuu/LMFjiI7lvgMXh7wlt9xLsIHvsV1r3BYwNGUDNAcUiHJA+Sy1fGYZYlkqsQzO9v9x7jVz0JdxB6qB5UvLm/i8A1fp1R2zh6uz98KTve+L3+fndBP4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GUrqL/gE; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="GUrqL/gE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C5FFE1F000FF; Thu, 17 Sep 2026 09:18:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789636685; bh=/Rhxw036vxujupFof0/OPSjDt69n/+Ot/zuxSne0Eqw=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=GUrqL/gEKSnTVaqEMvtTMGAJIeAc3r1NHdhkY/bcVnaqjDYy7u/nc9nEWQUY+dn8F XoCdbwTsnfZI8ojF1nF7YW4wAzKsG/p6LxqFNL0layDchsrDMBrwZqFZKqpUDmgC82 AAgiW7w74PRJm3hJ93xqiliY6Jn+nlnyhTRWnKnAP4ZLLnfMMGc8VagCQuSIIy5zqj 1r4lbKsNjJwkuUD40b9C1AROzPPdszzmoZNLncBcTqOgeSlgbdKtnuzSy2ivEkkYCE l0KXXuVRnw83JH7voMkIy6gHPECHSHHq25H36zaZiEwF/fBflCbjLSzYIn82/fQuUA vJgUsyHK8UIPg== From: Christian Brauner Date: Thu, 17 Sep 2026 11:17:33 +0200 Subject: [PATCH v2 6/7] signal: don't retarget shared signals in a dying thread group Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260917-work-coredump-fixes-v2-6-f3787fcda051@kernel.org> References: <20260917-work-coredump-fixes-v2-0-f3787fcda051@kernel.org> In-Reply-To: <20260917-work-coredump-fixes-v2-0-f3787fcda051@kernel.org> To: Oleg Nesterov , Jens Axboe , linux-fsdevel@vger.kernel.org Cc: 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=1800; i=brauner@kernel.org; h=from:subject:message-id; bh=QFgjXXUybA8CBQDzo0leFmaEK+XgKvIPes+QPTJhl4U=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWSt3mBSyypWda//OuPjubFXtBm/HNH9kSkm5b5ScNmR0 2m3X6cZdJSyMIhxMciKKbI4tJuEyy3nqdhslKkBM4eVCWQIAxenAEzkrw8jw4mVW053OxmfeSC4 o/1cFGP1m6bT/5ce4inKTqzcKJ2j8JeR4b+D9D2R2y1XvJcfks+YNGHNmdVTT9hce3JUVTb20pI /c5gA X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 If the calling thread has blocked a signal then retarget_shared_pending() slingshots a shared pending signal to a sibling thread. Today it only skips PF_EXITING threads but not a coredumping thread. But if SIGNAL_GROUP_EXIT is set no thread in the thread-group can dequeue such signals anymore as get_signal() sends SIGKILL to every thread and prepare_signal() drops any other signal. exit_signals() also returns early on SIGNAL_GROUP_EXIT. But neither sigprocmask() nor the mask restore in sigtimedwait() do. Say a thread sleeps in sigtimedwait() and a sibling thread crashes. The sleeping thread gets woken by the zap call. It restores its mask on the way out and retargets a signal that was queued for the coredumping process. That means TIF_SIGPENDING is set on the coredumping task which zap_threads() had cleared. So a blocking write sees TIF_SIGPENDING and truncates the dump. Stop retargeting signals when SIGNAL_GROUP_EXIT is set and avoid needlessly truncating coredumps. Fixes: e6fa16ab9c1e ("signal: sigprocmask() should do retarget_shared_pending()") Cc: stable@vger.kernel.org Signed-off-by: Christian Brauner (Amutable) --- kernel/signal.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/signal.c b/kernel/signal.c index d8bb1f168055..c3bad983dd37 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -3117,6 +3117,10 @@ static void retarget_shared_pending(struct task_struct *tsk, sigset_t *which) sigset_t retarget; struct task_struct *t; + /* Nobody dequeues them in a dying group, see get_signal(). */ + if (tsk->signal->flags & SIGNAL_GROUP_EXIT) + return; + sigandsets(&retarget, &tsk->signal->shared_pending.signal, which); if (sigisemptyset(&retarget)) return; -- 2.53.0