linux-kernel - [PATCH v4 24/33] mm: fall back to mmap_lock if vma->anon

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: <20230227173632.3292573-25-surenb@google.com>
Date:   Mon, 27 Feb 2023 09:36:23 -0800
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     akpm@...ux-foundation.org
Cc:     michel@...pinasse.org, jglisse@...gle.com, mhocko@...e.com,
        vbabka@...e.cz, hannes@...xchg.org, mgorman@...hsingularity.net,
        dave@...olabs.net, willy@...radead.org, liam.howlett@...cle.com,
        peterz@...radead.org, ldufour@...ux.ibm.com, paulmck@...nel.org,
        mingo@...hat.com, will@...nel.org, luto@...nel.org,
        songliubraving@...com, peterx@...hat.com, david@...hat.com,
        dhowells@...hat.com, hughd@...gle.com, bigeasy@...utronix.de,
        kent.overstreet@...ux.dev, punit.agrawal@...edance.com,
        lstoakes@...il.com, peterjung1337@...il.com, rientjes@...gle.com,
        chriscli@...gle.com, axelrasmussen@...gle.com, joelaf@...gle.com,
        minchan@...gle.com, rppt@...nel.org, jannh@...gle.com,
        shakeelb@...gle.com, tatashin@...gle.com, edumazet@...gle.com,
        gthelen@...gle.com, gurua@...gle.com, arjunroy@...gle.com,
        soheil@...gle.com, leewalsh@...gle.com, posk@...gle.com,
        michalechner92@...glemail.com, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: [PATCH v4 24/33] mm: fall back to mmap_lock if vma->anon_vma is not
 yet set

When vma->anon_vma is not set, page fault handler will set it by either
reusing anon_vma of an adjacent VMA if VMAs are compatible or by
allocating a new one. find_mergeable_anon_vma() walks VMA tree to find
a compatible adjacent VMA and that requires not only the faulting VMA
to be stable but also the tree structure and other VMAs inside that tree.
Therefore locking just the faulting VMA is not enough for this search.
Fall back to taking mmap_lock when vma->anon_vma is not set. This
situation happens only on the first page fault and should not affect
overall performance.

Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
---
 mm/memory.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/memory.c b/mm/memory.c
index bda4c1a991f0..8855846a361b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5243,6 +5243,10 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm,
 	if (!vma_is_anonymous(vma))
 		goto inval;
 
+	/* find_mergeable_anon_vma uses adjacent vmas which are not locked */
+	if (!vma->anon_vma)
+		goto inval;
+
 	if (!vma_start_read(vma))
 		goto inval;
 
-- 
2.39.2.722.g9855ee24e9-goog