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 A1F7D187C for ; Sat, 9 Dec 2023 12:35:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="xLyo329q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9AD9BC433C8; Sat, 9 Dec 2023 12:35:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1702125349; bh=2KEG3p5hQDJ3KVLITDzxV1RY0E37Db4DJYBFdRV8K+w=; h=Subject:To:Cc:From:Date:From; b=xLyo329qCPW3oEVm74fZxCUZH9aKDzVXghbYBePEYC1tEob/0Ho7NTwLGE6WoT7ox ih4cA3vIltDew4Y6ozZMHWybKDJxMQdE8t4GXWSJ4sjqGbWoik2ud8TISFzSVGvISz 2mIbAu3hjGMKqC4kW+4415Dp87iDe+HdQXkb1rr0= Subject: FAILED: patch "[PATCH] mm: fix oops when filemap_map_pmd() without prealloc_pte" failed to apply to 5.15-stable tree To: hughd@google.com,akpm@linux-foundation.org,david@redhat.com,jannh@google.com,jose.pekkarinen@foxhound.fi,kirill.shutemov@linux.intel.com,stable@vger.kernel.org,willy@infradead.org Cc: From: Date: Sat, 09 Dec 2023 13:35:45 +0100 Message-ID: <2023120945-citizen-library-9f46@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 9aa1345d66b8132745ffb99b348b1492088da9e2 # git commit -s git send-email --to '' --in-reply-to '2023120945-citizen-library-9f46@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: 9aa1345d66b8 ("mm: fix oops when filemap_map_pmd() without prealloc_pte") 03c4f20454e0 ("mm: introduce pmd_install() helper") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 9aa1345d66b8132745ffb99b348b1492088da9e2 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Fri, 17 Nov 2023 00:49:18 -0800 Subject: [PATCH] mm: fix oops when filemap_map_pmd() without prealloc_pte MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit syzbot reports oops in lockdep's __lock_acquire(), called from __pte_offset_map_lock() called from filemap_map_pages(); or when I run the repro, the oops comes in pmd_install(), called from filemap_map_pmd() called from filemap_map_pages(), just before the __pte_offset_map_lock(). The problem is that filemap_map_pmd() has been assuming that when it finds pmd_none(), a page table has already been prepared in prealloc_pte; and indeed do_fault_around() has been careful to preallocate one there, when it finds pmd_none(): but what if *pmd became none in between? My 6.6 mods in mm/khugepaged.c, avoiding mmap_lock for write, have made it easy for *pmd to be cleared while servicing a page fault; but even before those, a huge *pmd might be zapped while a fault is serviced. The difference in symptomatic stack traces comes from the "memory model" in use: pmd_install() uses pmd_populate() uses page_to_pfn(): in some models that is strict, and will oops on the NULL prealloc_pte; in other models, it will construct a bogus value to be populated into *pmd, then __pte_offset_map_lock() oops when trying to access split ptlock pointer (or some other symptom in normal case of ptlock embedded not pointer). Link: https://lore.kernel.org/linux-mm/20231115065506.19780-1-jose.pekkarinen@foxhound.fi/ Link: https://lkml.kernel.org/r/6ed0c50c-78ef-0719-b3c5-60c0c010431c@google.com Fixes: f9ce0be71d1f ("mm: Cleanup faultaround and finish_fault() codepaths") Signed-off-by: Hugh Dickins Reported-and-tested-by: syzbot+89edd67979b52675ddec@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-mm/0000000000005e44550608a0806c@google.com/ Reviewed-by: David Hildenbrand Cc: Jann Horn , Cc: José Pekkarinen Cc: Kirill A. Shutemov Cc: Matthew Wilcox (Oracle) Cc: [5.12+] Signed-off-by: Andrew Morton diff --git a/mm/filemap.c b/mm/filemap.c index 32eedf3afd45..f1c8c278310f 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3371,7 +3371,7 @@ static bool filemap_map_pmd(struct vm_fault *vmf, struct folio *folio, } } - if (pmd_none(*vmf->pmd)) + if (pmd_none(*vmf->pmd) && vmf->prealloc_pte) pmd_install(mm, vmf->pmd, &vmf->prealloc_pte); return false;