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 7283B19049B; Mon, 23 Jun 2025 21:51:51 +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=1750715511; cv=none; b=AmEz6OPPb9UqmesB9S7TWXVUbdE31h1G9zgTd8RXRQeMNa/9syOgDz1nIYcv1MpkzMITzp8i0CwJLYtZ5Nq2hP0iu5Fnx2hYExP3YfFvugThkcB51HpPlp10xDzW44sNywlvWKIflB459DSceHTcUiHXwM7Hh4pZzgpnKkNkFJ0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750715511; c=relaxed/simple; bh=HyQ9NMzJgdrcEn2Fge814HvIX9vURGKP9l6dvmDUq9I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=EI3QCc60YUS6Tg2EAr4p47eV7Ea9gX3rm9EU6xNmTs2FlSzCJR8yRDWpLyY8MuUWCMP9f9FGWpn4Q4oR10Iza4fTi4IU01mebekB2ovLi3ROSXqOkzP2tENloiD21weJ4pnZUvqc22v6GrudM0SxYAGK+h7vd82vj5RPSCOcrOI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=OAiB0xRY; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="OAiB0xRY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 05468C4CEEA; Mon, 23 Jun 2025 21:51:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750715511; bh=HyQ9NMzJgdrcEn2Fge814HvIX9vURGKP9l6dvmDUq9I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OAiB0xRYl9hXeVKeye3Q+nEHmLiLv+w7R5mWgC5ThpwOj4Cvmi1dhoxPJT57QZoNg 2K2go2wHMMGknf+xFxUYWZfoThFl5HVO3jZFDz2WZzeE01Sb8veSsHAP8cOl/k7/hB Jdvx0Xjovy0lpFwla+sRL9A4Qam33mBcnxKGKXMQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jann Horn , Lorenzo Stoakes , Liam Howlett , Muchun Song , Oscar Salvador , Vlastimil Babka , Andrew Morton Subject: [PATCH 5.10 300/355] mm/hugetlb: fix huge_pmd_unshare() vs GUP-fast race Date: Mon, 23 Jun 2025 15:08:21 +0200 Message-ID: <20250623130635.798706795@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250623130626.716971725@linuxfoundation.org> References: <20250623130626.716971725@linuxfoundation.org> User-Agent: quilt/0.68 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-Transfer-Encoding: 8bit 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jann Horn commit 1013af4f585fccc4d3e5c5824d174de2257f7d6d upstream. huge_pmd_unshare() drops a reference on a page table that may have previously been shared across processes, potentially turning it into a normal page table used in another process in which unrelated VMAs can afterwards be installed. If this happens in the middle of a concurrent gup_fast(), gup_fast() could end up walking the page tables of another process. While I don't see any way in which that immediately leads to kernel memory corruption, it is really weird and unexpected. Fix it with an explicit broadcast IPI through tlb_remove_table_sync_one(), just like we do in khugepaged when removing page tables for a THP collapse. Link: https://lkml.kernel.org/r/20250528-hugetlb-fixes-splitrace-v2-2-1329349bad1a@google.com Link: https://lkml.kernel.org/r/20250527-hugetlb-fixes-splitrace-v1-2-f4136f5ec58a@google.com Fixes: 39dde65c9940 ("[PATCH] shared page table for hugetlb page") Signed-off-by: Jann Horn Reviewed-by: Lorenzo Stoakes Cc: Liam Howlett Cc: Muchun Song Cc: Oscar Salvador Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/hugetlb.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5488,6 +5488,13 @@ int huge_pmd_unshare(struct mm_struct *m return 0; pud_clear(pud); + /* + * Once our caller drops the rmap lock, some other process might be + * using this page table as a normal, non-hugetlb page table. + * Wait for pending gup_fast() in other threads to finish before letting + * that happen. + */ + tlb_remove_table_sync_one(); atomic_dec(&virt_to_page(ptep)->pt_share_count); mm_dec_nr_pmds(mm); /*