From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 2054F8476 for ; Tue, 28 Mar 2023 14:55:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9605DC433EF; Tue, 28 Mar 2023 14:55:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1680015304; bh=Wp80y6qkWdGclHopOQLWUaD39UWzDDeZr//99EKIod0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Z1HuSL2B0xsWy868MSzTyeQatWSMlFkDMI8HVrkvKN65sV3MnvESKOdObwm/RicgS x6igARfElnwN++YjnpTVWRaVA+JyHe6RgE+kmIVmEX887StTP+EtUAtCc7t9+tktFl rlXU/Zru9xXnXnn8UdoZVfJqGW4LbNtc3EytlYKc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Liam R. Howlett" , Pengfei Xu , syzbot+2ee18845e89ae76342c5@syzkaller.appspotmail.com, David Hildenbrand , "Matthew Wilcox (Oracle)" , heng.su@intel.com, Andrew Morton Subject: [PATCH 6.2 233/240] mm/ksm: fix race with VMA iteration and mm_struct teardown Date: Tue, 28 Mar 2023 16:43:16 +0200 Message-Id: <20230328142629.418356442@linuxfoundation.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230328142619.643313678@linuxfoundation.org> References: <20230328142619.643313678@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Liam R. Howlett commit 6db504ce55bdbc575723938fc480713c9183f6a2 upstream. exit_mmap() will tear down the VMAs and maple tree with the mmap_lock held in write mode. Ensure that the maple tree is still valid by checking ksm_test_exit() after taking the mmap_lock in read mode, but before the for_each_vma() iterator dereferences a destroyed maple tree. Since the maple tree is destroyed, the flags telling lockdep to check an external lock has been cleared. Skip the for_each_vma() iterator to avoid dereferencing a maple tree without the external lock flag, which would create a lockdep warning. Link: https://lkml.kernel.org/r/20230308220310.3119196-1-Liam.Howlett@oracle.com Fixes: a5f18ba07276 ("mm/ksm: use vma iterators instead of vma linked list") Signed-off-by: Liam R. Howlett Reported-by: Pengfei Xu Link: https://lore.kernel.org/lkml/ZAdUUhSbaa6fHS36@xpf.sh.intel.com/ Reported-by: syzbot+2ee18845e89ae76342c5@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=64a3e95957cd3deab99df7cd7b5a9475af92c93e Acked-by: David Hildenbrand Cc: Matthew Wilcox (Oracle) Cc: Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/ksm.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) --- a/mm/ksm.c +++ b/mm/ksm.c @@ -988,9 +988,15 @@ static int unmerge_and_remove_all_rmap_i mm = mm_slot->slot.mm; mmap_read_lock(mm); + + /* + * Exit right away if mm is exiting to avoid lockdep issue in + * the maple tree + */ + if (ksm_test_exit(mm)) + goto mm_exiting; + for_each_vma(vmi, vma) { - if (ksm_test_exit(mm)) - break; if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) continue; err = unmerge_ksm_pages(vma, @@ -999,6 +1005,7 @@ static int unmerge_and_remove_all_rmap_i goto error; } +mm_exiting: remove_trailing_rmap_items(&mm_slot->rmap_list); mmap_read_unlock(mm);