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 ADB8028ED for ; Mon, 12 Dec 2022 13:20:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1405FC433D2; Mon, 12 Dec 2022 13:20:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1670851254; bh=RzbTZTsK13/UN4avQw0KFb9vkMz2TH4NpkGlBEwlGOs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aEu286Nk1RngTt7B2nXP6Jd5CM/pHyp2LbZdwNWjpzhIH9wKD/UWI4gLbrHBWKA8v 4C8kY1U+Es92xmzZ8IbkvRGv5M0sl7O17UYQPABax7dGKWImLOGTmDH2J0Vyj9jzL9 jVne76yHPl8uqP6ALpKMJ5sDH5P9E+0mILhhLqNY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jann Horn , David Hildenbrand , Yang Shi , John Hubbard , Peter Xu , Andrew Morton , Sasha Levin Subject: [PATCH 5.4 19/67] mm/khugepaged: invoke MMU notifiers in shmem/file collapse paths Date: Mon, 12 Dec 2022 14:16:54 +0100 Message-Id: <20221212130918.546610725@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221212130917.599345531@linuxfoundation.org> References: <20221212130917.599345531@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: Jann Horn commit f268f6cf875f3220afc77bdd0bf1bb136eb54db9 upstream. Any codepath that zaps page table entries must invoke MMU notifiers to ensure that secondary MMUs (like KVM) don't keep accessing pages which aren't mapped anymore. Secondary MMUs don't hold their own references to pages that are mirrored over, so failing to notify them can lead to page use-after-free. I'm marking this as addressing an issue introduced in commit f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages"), but most of the security impact of this only came in commit 27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP"), which actually omitted flushes for the removal of present PTEs, not just for the removal of empty page tables. Link: https://lkml.kernel.org/r/20221129154730.2274278-3-jannh@google.com Link: https://lkml.kernel.org/r/20221128180252.1684965-3-jannh@google.com Link: https://lkml.kernel.org/r/20221125213714.4115729-3-jannh@google.com Fixes: f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages") Signed-off-by: Jann Horn Acked-by: David Hildenbrand Reviewed-by: Yang Shi Cc: John Hubbard Cc: Peter Xu Cc: Signed-off-by: Andrew Morton [manual backport: this code was refactored from two copies into a common helper between 5.15 and 6.0] Signed-off-by: Jann Horn Signed-off-by: Sasha Levin --- mm/khugepaged.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index a8f2605cbd0d..8e67d2e5ff39 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1313,6 +1313,7 @@ void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) spinlock_t *ptl; int count = 0; int i; + struct mmu_notifier_range range; if (!vma || !vma->vm_file || vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE) @@ -1406,9 +1407,13 @@ void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) } /* step 4: collapse pmd */ + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm, haddr, + haddr + HPAGE_PMD_SIZE); + mmu_notifier_invalidate_range_start(&range); _pmd = pmdp_collapse_flush(vma, haddr, pmd); mm_dec_nr_ptes(mm); tlb_remove_table_sync_one(); + mmu_notifier_invalidate_range_end(&range); pte_free(mm, pmd_pgtable(_pmd)); i_mmap_unlock_write(vma->vm_file->f_mapping); @@ -1493,11 +1498,19 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) */ if (down_write_trylock(&mm->mmap_sem)) { if (!khugepaged_test_exit(mm)) { + struct mmu_notifier_range range; + + mmu_notifier_range_init(&range, + MMU_NOTIFY_CLEAR, 0, + NULL, mm, addr, + addr + HPAGE_PMD_SIZE); + mmu_notifier_invalidate_range_start(&range); /* assume page table is clear */ _pmd = pmdp_collapse_flush(vma, addr, pmd); mm_dec_nr_ptes(mm); tlb_remove_table_sync_one(); pte_free(mm, pmd_pgtable(_pmd)); + mmu_notifier_invalidate_range_end(&range); } up_write(&mm->mmap_sem); } else { -- 2.35.1