From 21169357ca913de9cef50da6f235a482b7a3cfab Mon Sep 17 00:00:00 2001
From: Fabricio Voznika <fvoznika@google.com>
Date: Thu, 10 Jun 2021 13:28:06 -0700
Subject: Add /proc/sys/vm/max_map_count

Set it to int32 max because gVisor doesn't have a limit.

Fixes #2337

PiperOrigin-RevId: 378722230
---
 pkg/sentry/fs/proc/sys.go           | 22 ++++++++++++++++++++++
 pkg/sentry/fsimpl/proc/tasks_sys.go |  1 +
 2 files changed, 23 insertions(+)

(limited to 'pkg')

diff --git a/pkg/sentry/fs/proc/sys.go b/pkg/sentry/fs/proc/sys.go
index b998fb75d..085aa6d61 100644
--- a/pkg/sentry/fs/proc/sys.go
+++ b/pkg/sentry/fs/proc/sys.go
@@ -77,6 +77,27 @@ func (*overcommitMemory) ReadSeqFileData(ctx context.Context, h seqfile.SeqHandl
 	}, 0
 }
 
+// +stateify savable
+type maxMapCount struct{}
+
+// NeedsUpdate implements seqfile.SeqSource.
+func (*maxMapCount) NeedsUpdate(int64) bool {
+	return true
+}
+
+// ReadSeqFileData implements seqfile.SeqSource.
+func (*maxMapCount) ReadSeqFileData(ctx context.Context, h seqfile.SeqHandle) ([]seqfile.SeqData, int64) {
+	if h != nil {
+		return nil, 0
+	}
+	return []seqfile.SeqData{
+		{
+			Buf:    []byte("2147483647\n"),
+			Handle: (*maxMapCount)(nil),
+		},
+	}, 0
+}
+
 func (p *proc) newKernelDir(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
 	h := hostname{
 		SimpleFileInode: *fsutil.NewSimpleFileInode(ctx, fs.RootOwner, fs.FilePermsFromMode(0444), linux.PROC_SUPER_MAGIC),
@@ -96,6 +117,7 @@ func (p *proc) newKernelDir(ctx context.Context, msrc *fs.MountSource) *fs.Inode
 
 func (p *proc) newVMDir(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
 	children := map[string]*fs.Inode{
+		"max_map_count":     seqfile.NewSeqFileInode(ctx, &maxMapCount{}, msrc),
 		"mmap_min_addr":     seqfile.NewSeqFileInode(ctx, &mmapMinAddrData{p.k}, msrc),
 		"overcommit_memory": seqfile.NewSeqFileInode(ctx, &overcommitMemory{}, msrc),
 	}
diff --git a/pkg/sentry/fsimpl/proc/tasks_sys.go b/pkg/sentry/fsimpl/proc/tasks_sys.go
index 88ab49048..2bc98a94f 100644
--- a/pkg/sentry/fsimpl/proc/tasks_sys.go
+++ b/pkg/sentry/fsimpl/proc/tasks_sys.go
@@ -55,6 +55,7 @@ func (fs *filesystem) newSysDir(ctx context.Context, root *auth.Credentials, k *
 			}),
 		}),
 		"vm": fs.newStaticDir(ctx, root, map[string]kernfs.Inode{
+			"max_map_count":     fs.newInode(ctx, root, 0444, newStaticFile("2147483647\n")),
 			"mmap_min_addr":     fs.newInode(ctx, root, 0444, &mmapMinAddrData{k: k}),
 			"overcommit_memory": fs.newInode(ctx, root, 0444, newStaticFile("0\n")),
 		}),
-- 
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