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 5640244DB64; Tue, 16 Jun 2026 16:04:53 +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=1781625894; cv=none; b=Q7oLNw3I+V0ID8CqGPvLKtYNu8J6C62IkO5ez/tTGpD7JX2KPGt+rSqr1ZaypmZfQPGq3OufCli/XvMyEns1YGMNmaf1f+XI24On85C+sl14AXFkVU6nX0g9RRPz9m5jYmwlAEFX21vmFU7Zl8Vj3+Hr2TUHDzPa5A17sW8mzdA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781625894; c=relaxed/simple; bh=XNzqxF0NQ8rcUo1MbArExBpZcnjjv8wVmwHdrRZKnao=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ViU8FLVZo9SR6g//WZESP+2zvNdezq3upbyMnvrE2DsPMlOT+zBy1Ww0fDIRwBrX3pI8sbkcYHjB3KoF3R+FLO3BNHYc6cwvlGBIQFnD3zyt6AOJqeNmy6oC3d9hrRvngBjg1ufSSCj/x+Ey7dNXz0R1PDnWrDK+svvRhKexCvI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=U6KPt4fl; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="U6KPt4fl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 075171F000E9; Tue, 16 Jun 2026 16:04:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1781625893; bh=Gvrle3mQqD05KF5TFrVe3ebfvaDeseIh4V2/aRIHQOw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=U6KPt4flf0o1Gm2DjaV3ATsB488wI8e0V2gZ0QFVDoTtC/DY7qSn6ZkKFpzZoTM4a 42td3TPw2p0yTSVsHIiYMFlJSFFTt9J07WGRKHbteWyjrC+dfhmAlY+V16dfsMlFtq 2uD2m4NccR8VALGmCtE3vxgPbBGzrI6QeBI9N/e4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yuan Tan , Yifan Wu , Juefei Pu , Xin Liu , Yilin Zhu , Ren Wei , Christian Brauner , Jeongjun Park , Kees Cook , Liam Howlett , Lorenzo Stoakes , Serge Hallyn , Vasiliy Kulikov , Davidlohr Bueso , Oleg Nesterov , Serge Hallyn , Andrew Morton Subject: [PATCH 6.18 228/325] ipc/shm: serialize orphan cleanup with shm_nattch updates Date: Tue, 16 Jun 2026 20:30:24 +0530 Message-ID: <20260616145109.751425796@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260616145057.827196531@linuxfoundation.org> References: <20260616145057.827196531@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yilin Zhu commit 2e5c6f4fd4001562781e99bbfc7f1f0127187542 upstream. shm_destroy_orphaned() walks the shm idr under shm_ids(ns).rwsem, but that does not serialize all fields tested by shm_may_destroy(). In particular, shm_nattch is updated while holding shm_perm.lock, and attach paths can do that without holding the rwsem. Do not decide that an orphaned segment is unused before taking the object lock. Move the shm_may_destroy() check under shm_perm.lock, matching the other destroy paths, and unlock the segment when it no longer qualifies for removal. Link: https://lore.kernel.org/9d97cc1031de2d0bace0edf3a668818aa2f4eca6.1777410234.git.zylzyl2333@gmail.com Fixes: 4c677e2eefdb ("shm: optimize locking and ipc_namespace getting") Reported-by: Yuan Tan Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Xin Liu Signed-off-by: Yilin Zhu Signed-off-by: Ren Wei Cc: Christian Brauner Cc: Jeongjun Park Cc: Kees Cook Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Serge Hallyn Cc: Vasiliy Kulikov Cc: Davidlohr Bueso Cc: Oleg Nesterov Cc: Serge Hallyn Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- ipc/shm.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) --- a/ipc/shm.c +++ b/ipc/shm.c @@ -418,15 +418,17 @@ static int shm_try_destroy_orphaned(int * We want to destroy segments without users and with already * exit'ed originating process. * - * As shp->* are changed under rwsem, it's safe to skip shp locking. + * shm_nattch can be changed under shm_perm.lock without holding the + * rwsem, so take the object lock before checking shm_may_destroy(). */ if (!list_empty(&shp->shm_clist)) return 0; - if (shm_may_destroy(shp)) { - shm_lock_by_ptr(shp); + shm_lock_by_ptr(shp); + if (shm_may_destroy(shp)) shm_destroy(ns, shp); - } + else + shm_unlock(shp); return 0; }