Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon,  9 Jan 2023 12:53:26 -0800
In-Reply-To: <20230109205336.3665937-1-surenb@google.com>
Mime-Version: 1.0
References: <20230109205336.3665937-1-surenb@google.com>
Message-ID: <20230109205336.3665937-32-surenb@google.com>
Subject: [PATCH 31/41] mm: prevent do_swap_page from handling page faults
 under VMA lock
From:   Suren Baghdasaryan <surenb@google.com>
To:     akpm@linux-foundation.org
Cc:     michel@lespinasse.org, jglisse@google.com, mhocko@suse.com,
        vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net,
        dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com,
        peterz@infradead.org, ldufour@linux.ibm.com,
        laurent.dufour@fr.ibm.com, paulmck@kernel.org, luto@kernel.org,
        songliubraving@fb.com, peterx@redhat.com, david@redhat.com,
        dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de,
        kent.overstreet@linux.dev, punit.agrawal@bytedance.com,
        lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com,
        axelrasmussen@google.com, joelaf@google.com, minchan@google.com,
        jannh@google.com, shakeelb@google.com, tatashin@google.com,
        edumazet@google.com, gthelen@google.com, gurua@google.com,
        arjunroy@google.com, soheil@google.com, hughlynch@google.com,
        leewalsh@google.com, posk@google.com, linux-mm@kvack.org,
        linux-arm-kernel@lists.infradead.org,
        linuxppc-dev@lists.ozlabs.org, x86@kernel.org,
        linux-kernel@vger.kernel.org, kernel-team@android.com,
        surenb@google.com
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Due to the possibility of do_swap_page dropping mmap_lock, abort fault
handling under VMA lock and retry holding mmap_lock. This can be handled
more gracefully in the future.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Laurent Dufour <laurent.dufour@fr.ibm.com>
---
 mm/memory.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/memory.c b/mm/memory.c
index 2560524ad7f4..20806bc8b4eb 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3707,6 +3707,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 	if (!pte_unmap_same(vmf))
 		goto out;
 
+	if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
+		ret = VM_FAULT_RETRY;
+		goto out;
+	}
+
 	entry = pte_to_swp_entry(vmf->orig_pte);
 	if (unlikely(non_swap_entry(entry))) {
 		if (is_migration_entry(entry)) {
-- 
2.39.0