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=1793306039; b=4tSIIaGar5gz4Mwj0mVXke9a4iTb8SS7ruqOLVyRlK/xhlqwDJSy7InNghr5Hj5VXNr2 Lwxxkca3BqqIh0AzzShgTshw8OIHU7aImtgJj+tNjFSV86MBjovSsd3hisw1VzGUY9hbF VqCzvvDKypC+8PU2o7ZdJIFMnj7lOQ67+zRpgsf1HHtZnorNKlwJ2KYFfq+LDkBJD0zHj rpq64620Hr+MUBgPT2oHUDAdkuqN1dfIeYyQ547JlpMmUkWSsCn9EMwWsY7FmIaYpcm8L rDY2HPyPs/eMlfLXDQ3v7ZAClzMfTbtmCaS8DwXnddyVgDHduEWXT4P5LjWNZ8FHssg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793306039; h=Received:DKIM-Signature:From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:References:In-Reply-To:To:Cc: X-Mailer:X-Developer-Signature:X-Developer-Key; bh=bDnFHMjA66BoQB8Vxjf4dtq2kXA91I+j2LTsXqWaqtA=; b=nV5r546RYmbLBwuKb/vz5ZsOT/vNcpJ1fFQnJsI1lF8BqEm2C7CSdPpTWxgEU4fhesoe 1zbR1TsXE4tmCL9zLHzWGC3BRCZC5zobpf1qzqZ7XcWEZv3sEQhVUCjNw/AWRk+ynGVtf DMYKXsoxMQxEoNB5JTNqAR6mAwWKgYM6D7j4mUfF1U0y1ifsJ3Dcm66iYHGE8jsZQ+iVc 6SbhqxZog9teew73XkSQvz1Tp/ZxyIXnnlYoXy7ydLkpVF1iLQEOi4bdvZCwVSPN5JpUu b61umzo++osarb1RGnofN/9NU8TCpCPoSp6bD0vL+c2k/ImAEiCwFocKXR90Bg6fpjw== 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=am3XTgpV; 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 82C29606A32A; Thu, 29 Oct 2026 20:33:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=am3XTgpV Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1D4651F01824; Thu, 29 Oct 2026 20:33:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793306039; bh=bDnFHMjA66BoQB8Vxjf4dtq2kXA91I+j2LTsXqWaqtA=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=am3XTgpVgHU7w4T2qNJKEWMRK6et1DuqCwcBz+lFGVUX9YclSBZSowWGPpIIV7+IM tEP5omw5Vzsc76le081/xL21kHFi0mU57Zo/UxYgrjd9vjFBziVfQWssZ6DxVCwwwd a5vGIMoc9rL00pdWDUba4bp8F+ajymkeQeip9JVHBkhVDQrqaZ0q/WtsV7R6RPztmZ o3Lqrrj2Hy4L/T8SbZDJ8rfKUMyvKC0VMztk5TIhdV5tescrZ1yrfhQDpQdMB9rocm /bxf+2RUoBuGOuMzXVjiDrWORAfn+A5CwB/wYWROwZHGu9vWzhfxTvQyxEW3T2w1yW 4Yac9xTxgMYlg== From: "David Hildenbrand (Arm)" Date: Thu, 29 Oct 2026 21:32:57 +0100 Subject: [PATCH v2 02/47] fork: take mmap_lock before copying mm_struct X-Mailing-List: linux-cxl@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: 7bit Message-Id: <20261029-fixes_core-v2-2-a64ce7f83abb@kernel.org> References: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> In-Reply-To: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> To: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, stable@vger.kernel.org, Josef Bacik , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3737; i=david@kernel.org; h=from:subject:message-id; bh=xdagUeG+am6KY+4B7movMSkDtyS1Wqo3jrGYGcvuKUc=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLIer225Nkv/lfLjom53y+5P53z+3H8sojjThvvT+idNq jkbHhaLdJSyMIhxMMiKKbIEBd83ePlyXW21Gx8zzBxWJpAhDFycAjCRr2cZfrM53Vy4zepghm7H g3RhgbUcrCeYBC7JSO3ie1J8widy9xZGhjmZn/qvLHE9ceaA4JXr89f/6bqY9Ma2s2ZalHXVw1B tTi4A X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A 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) 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 18b6dd851642..ee40142dab31 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 148ba01c0373..7618e72766a5 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 91ab65afda70..6c6f95329674 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; -- 2.43.0