From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794273667; b=bxxoT4eVK/QTPvwOVz1+WuSvket1jUwjaBuC60w+uJAMBbBPiFxAKCsI7HAEiYo6PUkC SNOyOUWXuOQGAbRlsWBawRbJ4K1a9jtjBkstxZB1FPI7j+5uVtWk2WZnXzoBJIvxjCsFe NbykZIZfIgZVCZf2NbeomDWeweYbqR3gthHbFZ+mzCTwqDJh4Ho+bPmTkua/PPScC10N4 3TITZDwwnaca09/UGW1qZLWtAa5+TWqpSU1xPrsnus0z6nX89sCmNfC+lMpvInItGVo3K FqFwl8OWlxGdAYBu/LTTk0B/BIgZd1IKZqbtqHLm9YNCJMfRn0u6YkrFXwypTkEBn/w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794273667; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=rtaUpEzL/+RQoGS//NDPg/RlSaz1eQNCygE+9esEz/0=; b=jK1qLarQzIPMg6nwQZ4YehWOCf6oUdaHMKmcT9YK0uqAmZjNdRda7zN1ToZlbldO+YGd NIEOAwz9W42fKYb774UAwgpbu1Pmj5A4TIdMHWPuL8Q+5dQYHQRbEplR4UZd4U4GEAB/U 4N+0jcpsN/rkMPIrAZ9ucIWH2Ywi6/Jb2Sx4k4CvhEN51vfmvu0VXdSn0+Uy40fiZDAWT SIfQjv63xNBFTAH8jD6tPHi6sJpo24HcM35PjbLqQPlqmT5RBaI+cyXawaOdl+2ak8jMG Hc1C+P5knAnoC8KZ6mVzj6+jY0TvlVu8bpRagqn5tAH6PpcbdHhnTIQuJ+/Pd2W2l3g== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=LOkaRPqT; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 453FB606A321 for ; Tue, 10 Nov 2026 01:21:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=LOkaRPqT Received: by smtp.kernel.org (Postfix) with ESMTPSA id CD87F1F008A3; Tue, 10 Nov 2026 01:21:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794273667; bh=rtaUpEzL/+RQoGS//NDPg/RlSaz1eQNCygE+9esEz/0=; h=From:To:Cc:Subject:Date; b=LOkaRPqTxZKJKC2/s+viKEmLBufzLjbgzar1zX0ucGRYE+W/ARBJ/D35YnrQA+su8 Ffn3KXiYz+4oGDtz/y2gtxaRofgDWtiMT2xRQWJuV3LQanJKSfh5F+M0cGnXJ6jh1a e5/eMRHT9wE3tPvjeRr/bPf640aJIkaXZtLD5dY5vMW6QDYxhNkOyWFq2UBo9rqqHB JXKN36zPMw/N3YydztQ8nLjdSeNabEKtP4zlb59IpT85tNycvJ5nku7GxXTQNqFJSy PKrZDOWfh7H07IZWdizzSp4HmvthUG69XqNny+i2hRmZueRft1yA4q7FIfz40gIDlB UHjRSdjfjXQrQ== From: Sasha Levin To: david@kernel.org, josef@toxicpanda.com, ljs@kernel.org, riel@surriel.com, vbabka@kernel.org, baohua@kernel.org, pfalcato@suse.de, harry@kernel.org, kas@kernel.org, sj@kernel.org, usama.anjum@arm.com Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] fork: take mmap_lock before copying mm_struct" failed to apply to 5.15-stable tree Date: Mon, 9 Nov 2026 20:21:04 -0500 Message-ID: <20261109202104-failed-5.15-ef694e2d2101@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x ef694e2d210111cc08c52fd25da9ab130170bfa3 # git commit -s git send-email --to '' --in-reply-to '20261109202104-failed-5.15-ef694e2d2101@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From ef694e2d210111cc08c52fd25da9ab130170bfa3 Mon Sep 17 00:00:00 2001 From: "David Hildenbrand (Arm)" Date: Sat, 31 Oct 2026 10:39:31 +0100 Subject: [PATCH] fork: take mmap_lock before copying mm_struct dup_mm() copies the parent's mm_struct before dup_mmap() takes the mmap_lock. A concurrent brk() can leave the child with a stale mm->brk and newer heap mappings, causing later brk() requests to fail. Other operations (e.g., PR_SET_MM) on the parent's mm_struct can similarly cause inconsistencies. As a simple and robust fix, grab the parent's mmap_lock earlier. This way we don't need to update individual mm fields in dup_mmap() and keep missing ones. Stop updating the 4 existing members (total_vm, data_vm, exec_vm, stack_vm), as that is now no longer required. Keep releasing the parent's mmap_lock in dup_mmap(), before userfaultfd completion, to avoid moving the userfaultfd handling into the caller. This should get cleaned up later. Move uprobe_start_dup_mmap() to preserve the lock ordering. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Reported-by: Josef Bacik Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Rik van Riel Reviewed-by: Vlastimil Babka (SUSE) Reviewed-by: Barry Song Reviewed-by: Pedro Falcato Reviewed-by: Harry Yoo (Meta) Reviewed-by: Kiryl Shutsemau (Meta) Reviewed-by: SJ Park Tested-by: Muhammad Usama Anjum Link: https://patch.msgid.link/20261031-fixes_core-v3-2-d6437171ecc3@kernel.org Signed-off-by: David Hildenbrand (Arm) --- kernel/fork.c | 20 ++++++++++++++------ mm/mmap.c | 8 +------- mm/nommu.c | 2 +- 3 files changed, 16 insertions(+), 14 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index 8b108ed371529..5efceb8d58a78 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1533,12 +1533,19 @@ static struct mm_struct *dup_mm(struct task_struct *tsk, if (!mm) goto fail_nomem; + uprobe_start_dup_mmap(); + if (mmap_write_lock_killable(oldmm)) { + free_mm(mm); + goto fail_uprobe; + } + memcpy(mm, oldmm, sizeof(*mm)); - if (!mm_init(mm, tsk)) - goto fail_nomem; + if (!mm_init(mm, tsk)) { + mmap_write_unlock(oldmm); + goto fail_uprobe; + } - uprobe_start_dup_mmap(); err = dup_mmap(mm, oldmm); if (err) goto free_pt; @@ -1557,9 +1564,10 @@ static struct mm_struct *dup_mm(struct task_struct *tsk, mm->binfmt = NULL; mm_init_owner(mm, NULL); mmput(mm); - if (err) - uprobe_end_dup_mmap(); - + if (!err) + return NULL; +fail_uprobe: + uprobe_end_dup_mmap(); fail_nomem: return NULL; } diff --git a/mm/mmap.c b/mm/mmap.c index 148ba01c03739..7618e72766a52 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1713,8 +1713,7 @@ __latent_entropy int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) LIST_HEAD(uf); VMA_ITERATOR(vmi, mm, 0); - if (mmap_write_lock_killable(oldmm)) - return -EINTR; + mmap_assert_write_locked(oldmm); flush_cache_dup_mm(oldmm); uprobe_dup_mmap(oldmm, mm); /* @@ -1725,11 +1724,6 @@ __latent_entropy int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) /* No ordering required: file already has been exposed. */ dup_mm_exe_file(mm, oldmm); - mm->total_vm = oldmm->total_vm; - mm->data_vm = oldmm->data_vm; - mm->exec_vm = oldmm->exec_vm; - mm->stack_vm = oldmm->stack_vm; - /* Use __mt_dup() to efficiently build an identical maple tree. */ retval = __mt_dup(&oldmm->mm_mt, &mm->mm_mt, GFP_KERNEL); if (unlikely(retval)) diff --git a/mm/nommu.c b/mm/nommu.c index 91ab65afda705..6c6f953296746 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -1887,7 +1887,7 @@ subsys_initcall(init_admin_reserve); int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) { - mmap_write_lock(oldmm); + mmap_assert_write_locked(oldmm); dup_mm_exe_file(mm, oldmm); mmap_write_unlock(oldmm); return 0; -- 2.53.0