linux-kernel - [PATCH v5 04/13] mm/shmem: Restrict MFD_INACCESSIBLE memory against RLIMIT

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Date:   Thu, 10 Mar 2022 22:09:02 +0800
From:   Chao Peng <chao.p.peng@...ux.intel.com>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-api@...r.kernel.org, qemu-devel@...gnu.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
        Hugh Dickins <hughd@...gle.com>,
        Jeff Layton <jlayton@...nel.org>,
        "J . Bruce Fields" <bfields@...ldses.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...nel.org>,
        Steven Price <steven.price@....com>,
        "Maciej S . Szmigiero" <mail@...iej.szmigiero.name>,
        Vlastimil Babka <vbabka@...e.cz>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        luto@...nel.org, jun.nakajima@...el.com, dave.hansen@...el.com,
        ak@...ux.intel.com, david@...hat.com
Subject: [PATCH v5 04/13] mm/shmem: Restrict MFD_INACCESSIBLE memory against RLIMIT_MEMLOCK

Since page migration / swapping is not supported yet, MFD_INACCESSIBLE
memory behave like longterm pinned pages and thus should be accounted to
mm->pinned_vm and be restricted by RLIMIT_MEMLOCK.

Signed-off-by: Chao Peng <chao.p.peng@...ux.intel.com>
---
 mm/shmem.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 7b43e274c9a2..ae46fb96494b 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -915,14 +915,17 @@ static void notify_fallocate(struct inode *inode, pgoff_t start, pgoff_t end)
 static void notify_invalidate_page(struct inode *inode, struct folio *folio,
 				   pgoff_t start, pgoff_t end)
 {
-#ifdef CONFIG_MEMFILE_NOTIFIER
 	struct shmem_inode_info *info = SHMEM_I(inode);
 
+#ifdef CONFIG_MEMFILE_NOTIFIER
 	start = max(start, folio->index);
 	end = min(end, folio->index + folio_nr_pages(folio));
 
 	memfile_notifier_invalidate(&info->memfile_notifiers, start, end);
 #endif
+
+	if (info->xflags & SHM_F_INACCESSIBLE)
+		atomic64_sub(end - start, &current->mm->pinned_vm);
 }
 
 /*
@@ -2680,6 +2683,20 @@ static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
 	return offset;
 }
 
+static bool memlock_limited(unsigned long npages)
+{
+	unsigned long lock_limit;
+	unsigned long pinned;
+
+	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
+	pinned = atomic64_add_return(npages, &current->mm->pinned_vm);
+	if (pinned > lock_limit && !capable(CAP_IPC_LOCK)) {
+		atomic64_sub(npages, &current->mm->pinned_vm);
+		return true;
+	}
+	return false;
+}
+
 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
 							 loff_t len)
 {
@@ -2753,6 +2770,12 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
 		goto out;
 	}
 
+	if ((info->xflags & SHM_F_INACCESSIBLE) &&
+			memlock_limited(end - start)) {
+		error = -ENOMEM;
+		goto out;
+	}
+
 	shmem_falloc.waitq = NULL;
 	shmem_falloc.start = start;
 	shmem_falloc.next  = start;
-- 
2.17.1