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 A631115C83 for ; Mon, 5 Dec 2022 19:32:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 28123C433C1; Mon, 5 Dec 2022 19:32:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1670268778; bh=hQHuqteUKcNzGKTh2KUNyAHHmISifaE/8HG6Lrrw4KA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KwS01QKtDxDeqg8ICygq6apbf7cOjGX+QTe6Q44D2ydf1PNEADv3Hic0z5ZXoNACQ +iPwuSDRIJVyRU3AXj8Ed0dmrDUEWDMW3Fzgi5Y/T+92tddXu3QGpXWUpHWodaZLns QRig3C3xStX2SVHoVExIcRE5954N6tcf31tnvcYI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Catalin Marinas , syzbot+c2c79c6d6eddc5262b77@syzkaller.appspotmail.com, Steven Price , Andrey Konovalov , Vincenzo Frascino , Will Deacon , Sasha Levin Subject: [PATCH 5.15 001/120] arm64: mte: Avoid setting PG_mte_tagged if no tags cleared or restored Date: Mon, 5 Dec 2022 20:09:01 +0100 Message-Id: <20221205190806.571868750@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221205190806.528972574@linuxfoundation.org> References: <20221205190806.528972574@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore 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: Catalin Marinas [ Upstream commit a8e5e5146ad08d794c58252bab00b261045ef16d ] Prior to commit 69e3b846d8a7 ("arm64: mte: Sync tags for pages where PTE is untagged"), mte_sync_tags() was only called for pte_tagged() entries (those mapped with PROT_MTE). Therefore mte_sync_tags() could safely use test_and_set_bit(PG_mte_tagged, &page->flags) without inadvertently setting PG_mte_tagged on an untagged page. The above commit was required as guests may enable MTE without any control at the stage 2 mapping, nor a PROT_MTE mapping in the VMM. However, the side-effect was that any page with a PTE that looked like swap (or migration) was getting PG_mte_tagged set automatically. A subsequent page copy (e.g. migration) copied the tags to the destination page even if the tags were owned by KASAN. This issue was masked by the page_kasan_tag_reset() call introduced in commit e5b8d9218951 ("arm64: mte: reset the page tag in page->flags"). When this commit was reverted (20794545c146), KASAN started reporting access faults because the overriding tags in a page did not match the original page->flags (with CONFIG_KASAN_HW_TAGS=y): BUG: KASAN: invalid-access in copy_page+0x10/0xd0 arch/arm64/lib/copy_page.S:26 Read at addr f5ff000017f2e000 by task syz-executor.1/2218 Pointer tag: [f5], memory tag: [f2] Move the PG_mte_tagged bit setting from mte_sync_tags() to the actual place where tags are cleared (mte_sync_page_tags()) or restored (mte_restore_tags()). Signed-off-by: Catalin Marinas Reported-by: syzbot+c2c79c6d6eddc5262b77@syzkaller.appspotmail.com Fixes: 69e3b846d8a7 ("arm64: mte: Sync tags for pages where PTE is untagged") Cc: # 5.14.x Cc: Steven Price Cc: Andrey Konovalov Cc: Vincenzo Frascino Cc: Will Deacon Link: https://lore.kernel.org/r/0000000000004387dc05e5888ae5@google.com/ Reviewed-by: Steven Price Link: https://lore.kernel.org/r/20221006163354.3194102-1-catalin.marinas@arm.com Signed-off-by: Catalin Marinas Signed-off-by: Sasha Levin --- arch/arm64/kernel/mte.c | 9 +++++++-- arch/arm64/mm/mteswap.c | 7 ++++++- 2 files changed, 13 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index dacca0684ea3..a3898bac5ae6 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -53,7 +53,12 @@ static void mte_sync_page_tags(struct page *page, pte_t old_pte, * the new page->flags are visible before the tags were updated. */ smp_wmb(); - mte_clear_page_tags(page_address(page)); + /* + * Test PG_mte_tagged again in case it was racing with another + * set_pte_at(). + */ + if (!test_and_set_bit(PG_mte_tagged, &page->flags)) + mte_clear_page_tags(page_address(page)); } void mte_sync_tags(pte_t old_pte, pte_t pte) @@ -69,7 +74,7 @@ void mte_sync_tags(pte_t old_pte, pte_t pte) /* if PG_mte_tagged is set, tags have already been initialised */ for (i = 0; i < nr_pages; i++, page++) { - if (!test_and_set_bit(PG_mte_tagged, &page->flags)) + if (!test_bit(PG_mte_tagged, &page->flags)) mte_sync_page_tags(page, old_pte, check_swap, pte_is_tagged); } diff --git a/arch/arm64/mm/mteswap.c b/arch/arm64/mm/mteswap.c index 7c4ef56265ee..fd6cabc6d033 100644 --- a/arch/arm64/mm/mteswap.c +++ b/arch/arm64/mm/mteswap.c @@ -62,7 +62,12 @@ bool mte_restore_tags(swp_entry_t entry, struct page *page) * the new page->flags are visible before the tags were updated. */ smp_wmb(); - mte_restore_page_tags(page_address(page), tags); + /* + * Test PG_mte_tagged again in case it was racing with another + * set_pte_at(). + */ + if (!test_and_set_bit(PG_mte_tagged, &page->flags)) + mte_restore_page_tags(page_address(page), tags); return true; } -- 2.35.1