linux-kernel - [PATCH 1/4] mm: allow guard regions in file-backed and read-only mappings

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <d885cb259174736c2830a5dfe07f81b214ef3faa.1739469950.git.lorenzo.stoakes@oracle.com>
Date: Thu, 13 Feb 2025 18:17:00 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Suren Baghdasaryan <surenb@...gle.com>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Matthew Wilcox <willy@...radead.org>, Vlastimil Babka <vbabka@...e.cz>,
        "Paul E . McKenney" <paulmck@...nel.org>, Jann Horn <jannh@...gle.com>,
        David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Shuah Khan <shuah@...nel.org>,
        linux-kselftest@...r.kernel.org, linux-api@...r.kernel.org,
        John Hubbard <jhubbard@...dia.com>, Juan Yescas <jyescas@...gle.com>,
        Kalesh Singh <kaleshsingh@...gle.com>
Subject: [PATCH 1/4] mm: allow guard regions in file-backed and read-only mappings

There is no reason to disallow guard regions in file-backed mappings -
readahead and fault-around both function correctly in the presence of PTE
markers, equally other operations relating to memory-mapped files function
correctly.

Additionally, read-only mappings if introducing guard-regions, only
restrict the mapping further, which means there is no violation of any
access rights by permitting this to be so.

Removing this restriction allows for read-only mapped files (such as
executable files) correctly which would otherwise not be permitted.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
 mm/madvise.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 6ecead476a80..e01e93e179a8 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1051,13 +1051,7 @@ static bool is_valid_guard_vma(struct vm_area_struct *vma, bool allow_locked)
 	if (!allow_locked)
 		disallowed |= VM_LOCKED;
 
-	if (!vma_is_anonymous(vma))
-		return false;
-
-	if ((vma->vm_flags & (VM_MAYWRITE | disallowed)) != VM_MAYWRITE)
-		return false;
-
-	return true;
+	return !(vma->vm_flags & disallowed);
 }
 
 static bool is_guard_pte_marker(pte_t ptent)
-- 
2.48.1