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 0B7F412B94; Thu, 15 Oct 2026 22:58:16 +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=1792105099; cv=none; b=H7DzjI25xkuBhCfhKEBmqdezijjps+EdW3lQhmhh5q9VyKgYzZ9WO77tz8XjgMUlDIIY6ZHCa40Y9MR/TnN34rWRijyeF1lurM1EV8TF2PqKCqXU4WMmyTjaoEYuA2/IvQ15AQX8HVIyOg1lIZyypCueYeFHLZBONxk8FWDMXdw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792105099; c=relaxed/simple; bh=ZvVfpvFZJiDo30GkPH0cbd3rziqUXN70WspPh3eBQ64=; h=Date:To:From:Subject:Message-Id; b=Bfra1dGM9PgX+x+J/dinM6gpRxGVRx44dwCtgs5DwzrqXMW6mP2+2Db35J6ElbnTynuVa3ovc26HqHpsfvBYeGQbCG7OP754BIv8qEWwV6T4zM1tB/7lOs0pUOMc8yhGujSkUf8Vh8e9S8ODPyKmBWflVwcKhlfzdQaCiw/+otc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=UUPXqsBK; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="UUPXqsBK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 73C801F000C4; Thu, 15 Oct 2026 22:58:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1792105096; bh=8b0EtdAuKO46RgstjAFS/jsRY6RpJ3wLJj0UDzt0Vi8=; h=Date:To:From:Subject; b=UUPXqsBKbx7Tvi6hczZVaRqPegEjSTkmmMs8cHVd29VhPnAKMDER7tyNYF8LYyj5/ Y8DF/FRVdNV3MOA+VSIqw2rdOO3RPJvegFIyj9nxejA3lJfAAAPgABTpOUdP7WavcQ hyGZaKEEHGOstFg5eawg1daYga3BZLXg5LvtJPeE= Date: Thu, 15 Oct 2026 15:58:15 -0700 To: mm-commits@vger.kernel.org,vbabka@kernel.org,stable@vger.kernel.org,rppt@kernel.org,riel@surriel.com,pfalcato@suse.de,peterx@redhat.com,osalvador@suse.de,nao.horiguchi@gmail.com,muchun.song@linux.dev,mel@csn.ul.ie,ljs@kernel.org,linmiaohe@huawei.com,liam@infradead.org,kas@kernel.org,jannh@google.com,david@kernel.org,agl@us.ibm.com,josef@toxicpanda.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-vma-dont-leak-the-commit-charge-on-mmap-failure.patch added to mm-hotfixes-unstable branch Message-Id: <20261015225816.73C801F000C4@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/vma: don't leak the commit charge on mmap failure has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-vma-dont-leak-the-commit-charge-on-mmap-failure.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vma-dont-leak-the-commit-charge-on-mmap-failure.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Josef Bacik Subject: mm/vma: don't leak the commit charge on mmap failure Date: Thu, 15 Oct 2026 18:07:07 +0200 Patch series "mm: various (urgent?) fixes", v1. Here are various MM fixes. The majority was reported by Josef at Anthrophic, the remainder was found while reviewing/overhauling them. Two issues/fixes reported are not included, as we are discussing (better) alternatives on the list already. I left most of the original commit messages as schloppy as they are: I don't particularly care as long as the code is in good shape and as long as they are not actively wrong. But I (and Mike) could not be stopped from overhauling at least some of them. While I don't think there is anything too critical in here, I think this is a good opportunity to see how fast we can get pre-screened/pre-reviewed fixes upstream that might be security-related. The majority are hugetlb + uffd issues, that are not actually that relevant for most installations. But all things that should just get fixed. Some uffd fixes need proper follow ups to fix some more of the root causes of leftover UFFD PTE bits (or proof that there are none remaining). This patch (of 10): When an accountable mapping replaces existing mappings (MAP_FIXED), __mmap_setup() only charges the difference between the size of the new mapping and the VM_ACCOUNT pages it replaces. It then zeroes vms->nr_accounted so that unmapping the old VMAs does not return their charge, which now backs the new mapping. If the operation fails after that point, the error path returns map->charged, i.e. only the difference. By then vms_clean_up_area() has zapped the page tables and closed the old VMAs, so vms_abort_munmap_vmas() cannot reattach them. It leaves a gap and finishes the unmap with vms_complete_munmap_vmas(), which uncharges vms->nr_accounted == 0 pages. The old VMAs are gone, the new one was never created, and the charge of the old ones is never returned, not even when the process exits. No privilege is needed to hit this, only a file whose mmap hook fails, for example a socket (sock_no_mmap() returns -ENODEV): p = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); mmap(p, len, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_FIXED, socket_fd, 0); Every iteration adds len to Committed_AS for good. With vm.overcommit_memory=2 this lets any user make all further accountable allocations in the system fail with -ENOMEM. Once the new mapping has taken over the charge of the mappings it replaces, it owns the charge for all of its pages. Record that in map->charged, so that the error path returns all of it. A failure in __mmap_setup() itself is not affected: it happens before the charge is taken over and the old VMAs are reattached with their charge intact. Original fix generated by an LLM and sent in private by Josef. Link: https://lore.kernel.org/20261015-urgent_fixes-v1-0-42796911043b@kernel.org Link: https://lore.kernel.org/20261015-urgent_fixes-v1-1-42796911043b@kernel.org Fixes: 4f87153e82c4 ("mm: change failure of MAP_FIXED to restoring the gap on failure") Signed-off-by: Josef Bacik Signed-off-by: David Hildenbrand (Arm) Signed-off-by: Andrew Morton Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Pedro Falcato Cc: Liam R. Howlett Cc: Vlastimil Babka Cc: Jann Horn Cc: Muchun Song Cc: Oscar Salvador Cc: Miaohe Lin Cc: Naoya Horiguchi Cc: Adam Litke Cc: Mel Gorman Cc: Rik van Riel Cc: Peter Xu Cc: Kiryl Shutsemau Cc: Mike Rapoport Cc: [ david: call variable "uncharged" and make it const, adjust/simplify comments ] --- mm/vma.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) --- a/mm/vma.c~mm-vma-dont-leak-the-commit-charge-on-mmap-failure +++ a/mm/vma.c @@ -2577,14 +2577,17 @@ static int __mmap_setup(struct mmap_stat /* Private writable mapping: check memory availability. */ if (accountable_mapping(map)) { - map->charged = map->pglen; - map->charged -= vms->nr_accounted; - if (map->charged) { - error = security_vm_enough_memory_mm(map->mm, map->charged); + const unsigned long uncharged = map->pglen - vms->nr_accounted; + + /* Charge only what's not already charged by mappings we replace. */ + if (uncharged) { + error = security_vm_enough_memory_mm(map->mm, uncharged); if (error) return error; } + /* Our new mapping owns the entire charge now. */ + map->charged = map->pglen; vms->nr_accounted = 0; vma_flags_set(&map->vma_flags, VMA_ACCOUNT_BIT); } _ Patches currently in -mm which might be from josef@toxicpanda.com are mm-vma-dont-leak-the-commit-charge-on-mmap-failure.patch mm-hugetlb-fix-use-after-free-of-a-new-anon-folio.patch mm-hugetlb-unmap-the-page-where-the-other-vma-maps-it.patch mm-hugetlb-dont-clear-the-resv_map-of-a-vma-whose-lock-is-held.patch mm-hugetlb-fix-endless-write-fault-on-a-leftover-uffd-bit.patch mm-hugetlb-dont-leave-a-uffd-wp-marker-when-zapping-an-rwp-entry.patch