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 BF26125B305 for ; Fri, 27 Mar 2026 17:23:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774632219; cv=none; b=Er8fg8+f2u+99+owhjyOCgEIUCrsAslcuX8tpZ1QfTO64d0c0CQTZkA/RDt6w4D0kI1eqsyBNsvYnQD0rcdJnI19psu4b7VOwGfZFiCZUsg/PRjKSyYlR8dvVnTP4qPU6LhiU4hdyf7qqbAh6ufGhRDbD8i4I/NBS/cbvUXxMps= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774632219; c=relaxed/simple; bh=LoOchEM2GvaQU0UW3QW6MbbvCC9O/qqhrAJClJpoxu4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=rmNdJZF3HB8zNpdwQoE1CjpgZb/PXdhI5qTcCzcC/zK7YBJV/mNFgUiAtbTiDbZZj3oawGGrgIN+0DkvHQhT3QhNwocRD+w0mmfBOjQfS5RIqV9U6NTfzodMIH2SMBYdpaJxnXp5/fjyojvxMz4dwlQTwBbjfOenrtOpT4YRaco= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HNCHYGGP; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HNCHYGGP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EAA4DC19423; Fri, 27 Mar 2026 17:23:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774632219; bh=LoOchEM2GvaQU0UW3QW6MbbvCC9O/qqhrAJClJpoxu4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=HNCHYGGPgWiQAgkcynJCD/IJaQuDDouTkXWQZInqCQNdpvJRtJ/6j/MKJVojDfQaY zbelBuWulqNyUmZXmCyq0NNF3GriNaxWMyLyf/EMEx7kJgcjcfBmMvCh/um/RoxyVA MNJN8WL5rNgGkRkNCelbxtJFDnuyHLGkooTsqbHUSiV4EJylYAtGtEoBgAG5uPlC/D GsJzkvcIMs2BE5pKbjw6EYCHhddZnbGBKmn7LX9wrrVAYx8bS2fuEBcPESbX6oyolB yKUOCZcyw5S6FNAnsZCXWyZ6mFNgOB//n8v8gVdQdoOUNI8sLylXjmXvlghctxG/x7 SBr4OKna1kNTw== Date: Fri, 27 Mar 2026 17:23:34 +0000 From: "Lorenzo Stoakes (Oracle)" To: "David Hildenbrand (Arm)" Cc: Andrew Morton , "Liam R . Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , Jeff Xu , linux-mm@kvack.org, linux-kernel@vger.kernel.org, antonius Subject: Re: [PATCH mm-hotfixes] mm/mseal: update VMA end correctly on merge Message-ID: <5739bab8-d75f-404d-a3c8-a67f91e072a5@lucifer.local> References: <20260327090640.146308-1-ljs@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Mar 27, 2026 at 05:57:06PM +0100, David Hildenbrand (Arm) wrote: > On 3/27/26 10:06, Lorenzo Stoakes (Oracle) wrote: > > Previously we stored the end of the current VMA in curr_end, and then upon > > iterating to the next VMA updated curr_start to curr_end to advance to the > > next VMA. > > > > However, this doesn't take into account the fact that a VMA might be > > updated due to a merge by vma_modify_flags(), which can result in curr_end > > being stale and thus, upon setting curr_start to curr_end, ending up with > > an incorrect curr_start on the next iteration. > > > > Resolve the issue by setting curr_end to vma->vm_end unconditionally to > > ensure this value remains updated should this occur. > > > > Signed-off-by: Lorenzo Stoakes (Oracle) > > Fixes: 6c2da14ae1e0 ("mm/mseal: rework mseal apply logic") > > Cc: > > Reported-by: Antonius > > Closes: https://lore.kernel.org/linux-mm/CAK8a0jyHXqBpt8Xe8v9SNDbnRiwz7OthA8SKY=NLRY7smPEP3Q@mail.gmail.com/ > > --- > > mm/mseal.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/mm/mseal.c b/mm/mseal.c > > index 316b5e1dec78..2d72a15d8ea1 100644 > > --- a/mm/mseal.c > > +++ b/mm/mseal.c > > @@ -66,7 +66,7 @@ static int mseal_apply(struct mm_struct *mm, > > prev = vma; > > > > for_each_vma_range(vmi, vma, end) { > > - const unsigned long curr_end = MIN(vma->vm_end, end); > > + unsigned long curr_end = MIN(vma->vm_end, end); > > > > if (!(vma->vm_flags & VM_SEALED)) { > > vm_flags_t vm_flags = vma->vm_flags | VM_SEALED; > > @@ -76,6 +76,7 @@ static int mseal_apply(struct mm_struct *mm, > > if (IS_ERR(vma)) > > return PTR_ERR(vma); > > vm_flags_set(vma, VM_SEALED); > > + curr_end = vma->vm_end; /* Merge may have updated. */ > > } > > > I was a bit confused why curr_start is allowed to not start within the VMA, > but before it. Then I recalled that range_contains_unmapped() checks for no holes. > > > Would the following also sort out the problem and even simplify the code? > > diff --git a/mm/mseal.c b/mm/mseal.c > index 603df53ad267..e2093ae3d25c 100644 > --- a/mm/mseal.c > +++ b/mm/mseal.c > @@ -56,7 +56,6 @@ static int mseal_apply(struct mm_struct *mm, > unsigned long start, unsigned long end) > { > struct vm_area_struct *vma, *prev; > - unsigned long curr_start = start; > VMA_ITERATOR(vmi, mm, start); > > /* We know there are no gaps so this will be non-NULL. */ > @@ -66,6 +65,7 @@ static int mseal_apply(struct mm_struct *mm, > prev = vma; > > for_each_vma_range(vmi, vma, end) { > + const unsigned long curr_start = MAX(vma->vm_start, start); Yeah that's nice :) > const unsigned long curr_end = MIN(vma->vm_end, end); > > if (!vma_test(vma, VMA_SEALED_BIT)) { > @@ -82,7 +82,6 @@ static int mseal_apply(struct mm_struct *mm, > } > > prev = vma; > - curr_start = curr_end; > } > > return 0; > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > > I might be wrong about that, I've been staring at the screen for too long today. No this is better, I've mulled this over, this is much better :) Sorry to be a pain Andrew - let me respin this right now. I will retain tags as this is functionally equivalent, I have checked it locally, confirmed repro solved, checked against AI review also. > > > -- > Cheers, > > David Cheers, Lorenzo