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 61227434E21 for ; Wed, 5 Aug 2026 12:19:54 +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=1785932395; cv=none; b=hLRGu6A49lsn5cpMXyft0AD8Prcsm03mMqRN3n+qECqKYx+2JPx1C1+YWEaiBGk6SDqs96AJw5M6Xhy6RZ0n90o0Y9VS8wI16FxXNtuy8m7lZMQE+wbF1CjY7o+ClzijAORkd66DCPo9y39hnLi6LbrhAi5TyHA/XOP+mQujSdE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785932395; c=relaxed/simple; bh=OyeMpm0jq3Br7SAELSgWuone7yaW++r/K5mCzoPdRto=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=cIJ2Xxi5PSglf809Mih3KYuiY1b2fWIbzkmwqT0nVamv0i7GwVigbkT2bQkrSpBwmwn4EEKDjAqIBd377OKCXsLixoGcgNlNtJayi+EWaJ7YScaW2F6tj4nf5+ng9LplmXUL7hC4C+eetyhU5H4PNAdd9rXZyT3MG9F/VI4TqTQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=b9LRIgne; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="b9LRIgne" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BFD641F00A3A; Wed, 5 Aug 2026 12:19:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785932394; bh=oE6PLk6zhamRDU5bmWB+c40IOBnOp6EGpgDAJsyDXVs=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=b9LRIgnew9rjfCXDGHdWBSbm4sDoGzDwTOncLSU5VTsVzU/OQXY257koPpb3fp++7 +B+yWQ+c8azWeAP8SuDqmZS8xhl+K7UdqBJb6LqXnCEelNWm98hByR39CNOxoLOcA7 DYd3xgYxQHy7PXT8ycDUxEbf/9D9q7KsKEFyh7gVhFazdad9SakRJLyK7kTLXYotUL aqEH0IRc2Z8cbZZf4DYbyrBbg7TnlXrAuQykitld2ekeBXDXHIW8AmFb989pLJvVvu YhYZPxeKAUmVW8kRnRosz93eYv2hjc6WYklu62QSWmo90FPhjLuPZep4cukFfuGH10 hqKbZeY7kvjOg== Message-ID: <72f017f2-89c5-4e4a-9ce3-ab79f70b04a0@kernel.org> Date: Wed, 5 Aug 2026 14:19:49 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] mm/ksm: validate KSM rmap items before hwpoison kill To: Longlong Xia , akpm@linux-foundation.org, "Lorenzo Stoakes (Arm)" Cc: xu.xin16@zte.com.cn, chengming.zhou@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Longlong Xia References: <20260803151151.3472893-1-xialonglong2025@163.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/3/26 17:11, Longlong Xia wrote: > From: Longlong Xia > > collect_procs_ksm() walks the stable-node rmap list and queues an > early kill for every task whose mm appears on the anon_vma chain. > > That rmap item can be stale by the time memory failure handles the > poisoned KSM page. A VMA may have been split, unmapped or remapped > after the rmap item was recorded, so matching only vma->vm_mm can send > SIGBUS with an address that no longer maps the poisoned page. > > Check that the saved address still belongs to the VMA and that > page_vma_mapped_walk() still finds the poisoned page there before > adding the task to the kill list. > > Fixes: 4248d0083ec5 ("mm: ksm: support hwpoison for ksm page") > Signed-off-by: Longlong Xia > --- > mm/ksm.c | 27 +++++++++++++++++++++++++-- > 1 file changed, 25 insertions(+), 2 deletions(-) > > diff --git a/mm/ksm.c b/mm/ksm.c > index 7d5b76478f0b..bc4b2dd894d8 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -3222,6 +3222,27 @@ void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc) > } > > #ifdef CONFIG_MEMORY_FAILURE > +static bool ksm_rmap_item_mapped(const struct page *page, > + struct vm_area_struct *vma, > + unsigned long addr) Two tab indent on second parameter line struct vm_area_struct *vma, unsigned long addr) > +{ > + struct page_vma_mapped_walk pvmw = { > + .pfn = page_to_pfn(page), > + .nr_pages = 1, > + .vma = vma, > + .address = addr, > + .flags = PVMW_SYNC, > + }; > + > + if (addr < vma->vm_start || addr >= vma->vm_end) > + return false; > + if (!page_vma_mapped_walk(&pvmw)) > + return false; > + page_vma_mapped_walk_done(&pvmw); > + We have page_mapped_in_vma(). So I wonder whether we can find a way to 1) Modify to just work with KSM (CCing Lorenzo) Maybe it already does. I'm confused as so often. Looking at the existing caller collect_procs_anon(), it's really only called on anon folios. Could it already be called on KSM folios? What would happen in that case? (does it just work because folio->index is still what we expect) 2) Do the following diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c index d7670ba4147bf..7eeb3c336cfe9 100644 --- a/mm/page_vma_mapped.c +++ b/mm/page_vma_mapped.c @@ -342,6 +342,27 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) } #ifdef CONFIG_MEMORY_FAILURE +static unsigned long page_mapped_in_vma_at_address(const struct page *page, + struct vm_area_struct *vma, unsigned long addr) +{ + const struct folio *folio = page_folio(page); + struct page_vma_mapped_walk pvmw = { + .pfn = page_to_pfn(page), + .nr_pages = 1, + .vma = vma, + .address = addr, + .flags = PVMW_SYNC, + }; + + if (addr < vma->vm_start || addr >= vma->vm_end) + return -EFAULT; + if (!page_vma_mapped_walk(&pvmw)) + return -EFAULT; + page_vma_mapped_walk_done(&pvmw); +out: + return pvmw.address; +} + /** * page_mapped_in_vma - check whether a page is really mapped in a VMA * @page: the page to test @@ -355,21 +376,10 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) unsigned long page_mapped_in_vma(const struct page *page, struct vm_area_struct *vma) { - const struct folio *folio = page_folio(page); - struct page_vma_mapped_walk pvmw = { - .pfn = page_to_pfn(page), - .nr_pages = 1, - .vma = vma, - .flags = PVMW_SYNC, - }; + const unsigned long addr = vma_address(vma, page_pgoff(folio, page), 1); - pvmw.address = vma_address(vma, page_pgoff(folio, page), 1); - if (pvmw.address == -EFAULT) - goto out; - if (!page_vma_mapped_walk(&pvmw)) + if (addr == -EFAULT) return -EFAULT; - page_vma_mapped_walk_done(&pvmw); -out: - return pvmw.address; + return page_mapped_in_vma_at_address(page, vma, addr); } #endif > + return true; > +} > + > /* > * Collect processes when the error hit an ksm page. > */ > @@ -3237,13 +3258,13 @@ void collect_procs_ksm(const struct folio *folio, const struct page *page, > if (!stable_node) > return; > hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) { > + unsigned long addr = rmap_item->address & PAGE_MASK; Can be const. > struct anon_vma *av = rmap_item->anon_vma; > > anon_vma_lock_read(av); > rcu_read_lock(); > for_each_process(tsk) { > struct anon_vma_chain *vmac; > - unsigned long addr; > struct task_struct *t = > task_early_kill(tsk, force_early); > if (!t) > @@ -3253,7 +3274,9 @@ void collect_procs_ksm(const struct folio *folio, const struct page *page, > { > vma = vmac->vma; > if (vma->vm_mm == t->mm) { > - addr = rmap_item->address & PAGE_MASK; > + if (!ksm_rmap_item_mapped(page, vma, > + addr)) jut put that onto a single line, please: easier to read. > + continue; > add_to_kill_ksm(t, page, vma, to_kill, > addr); > } -- Cheers, David