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authorJamie Liu <jamieliu@google.com>2020-08-25 16:38:07 -0700
committergVisor bot <gvisor-bot@google.com>2020-08-25 16:40:02 -0700
commit247dcd62d436943ad0bf8455c2be22bc36da6637 (patch)
tree8b59371a081ccc1a658cc074ee786ffc1ca0b0ef
parentcb573c8e0bf042ea111dc83c72f25d135623032f (diff)
Return non-zero size for tmpfs statfs(2).
This does not implement accepting or enforcing any size limit, which will be more complex and has performance implications; it just returns a fixed non-zero size. Updates #1936 PiperOrigin-RevId: 328428588
-rw-r--r--pkg/abi/linux/fs.go11
-rw-r--r--pkg/sentry/fs/tmpfs/tmpfs.go12
-rw-r--r--pkg/sentry/fsimpl/tmpfs/filesystem.go12
-rw-r--r--pkg/sentry/fsimpl/tmpfs/tmpfs.go24
4 files changed, 41 insertions, 18 deletions
diff --git a/pkg/abi/linux/fs.go b/pkg/abi/linux/fs.go
index 158d2db5b..2b1ef0d4e 100644
--- a/pkg/abi/linux/fs.go
+++ b/pkg/abi/linux/fs.go
@@ -44,17 +44,18 @@ type Statfs struct {
// Type is one of the filesystem magic values, defined above.
Type uint64
- // BlockSize is the data block size.
+ // BlockSize is the optimal transfer block size in bytes.
BlockSize int64
- // Blocks is the number of data blocks in use.
+ // Blocks is the maximum number of data blocks the filesystem may store, in
+ // units of BlockSize.
Blocks uint64
- // BlocksFree is the number of free blocks.
+ // BlocksFree is the number of free data blocks, in units of BlockSize.
BlocksFree uint64
- // BlocksAvailable is the number of blocks free for use by
- // unprivileged users.
+ // BlocksAvailable is the number of data blocks free for use by
+ // unprivileged users, in units of BlockSize.
BlocksAvailable uint64
// Files is the number of used file nodes on the filesystem.
diff --git a/pkg/sentry/fs/tmpfs/tmpfs.go b/pkg/sentry/fs/tmpfs/tmpfs.go
index b095312fe..998b697ca 100644
--- a/pkg/sentry/fs/tmpfs/tmpfs.go
+++ b/pkg/sentry/fs/tmpfs/tmpfs.go
@@ -16,6 +16,8 @@
package tmpfs
import (
+ "math"
+
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/sentry/fs"
@@ -32,9 +34,15 @@ import (
var fsInfo = fs.Info{
Type: linux.TMPFS_MAGIC,
+ // tmpfs currently does not support configurable size limits. In Linux,
+ // such a tmpfs mount will return f_blocks == f_bfree == f_bavail == 0 from
+ // statfs(2). However, many applications treat this as having a size limit
+ // of 0. To work around this, claim to have a very large but non-zero size,
+ // chosen to ensure that BlockSize * Blocks does not overflow int64 (which
+ // applications may also handle incorrectly).
// TODO(b/29637826): allow configuring a tmpfs size and enforce it.
- TotalBlocks: 0,
- FreeBlocks: 0,
+ TotalBlocks: math.MaxInt64 / usermem.PageSize,
+ FreeBlocks: math.MaxInt64 / usermem.PageSize,
}
// rename implements fs.InodeOperations.Rename for tmpfs nodes.
diff --git a/pkg/sentry/fsimpl/tmpfs/filesystem.go b/pkg/sentry/fsimpl/tmpfs/filesystem.go
index 7924a0911..eddfeab76 100644
--- a/pkg/sentry/fsimpl/tmpfs/filesystem.go
+++ b/pkg/sentry/fsimpl/tmpfs/filesystem.go
@@ -25,7 +25,6 @@ import (
"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
"gvisor.dev/gvisor/pkg/sentry/vfs"
"gvisor.dev/gvisor/pkg/syserror"
- "gvisor.dev/gvisor/pkg/usermem"
)
// Sync implements vfs.FilesystemImpl.Sync.
@@ -706,16 +705,7 @@ func (fs *filesystem) StatFSAt(ctx context.Context, rp *vfs.ResolvingPath) (linu
if _, err := resolveLocked(ctx, rp); err != nil {
return linux.Statfs{}, err
}
- statfs := linux.Statfs{
- Type: linux.TMPFS_MAGIC,
- BlockSize: usermem.PageSize,
- FragmentSize: usermem.PageSize,
- NameLength: linux.NAME_MAX,
- // TODO(b/29637826): Allow configuring a tmpfs size and enforce it.
- Blocks: 0,
- BlocksFree: 0,
- }
- return statfs, nil
+ return globalStatfs, nil
}
// SymlinkAt implements vfs.FilesystemImpl.SymlinkAt.
diff --git a/pkg/sentry/fsimpl/tmpfs/tmpfs.go b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
index 428f62aaa..a7fdf19ca 100644
--- a/pkg/sentry/fsimpl/tmpfs/tmpfs.go
+++ b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
@@ -201,6 +201,25 @@ func (fs *filesystem) Release(ctx context.Context) {
fs.vfsfs.VirtualFilesystem().PutAnonBlockDevMinor(fs.devMinor)
}
+// immutable
+var globalStatfs = linux.Statfs{
+ Type: linux.TMPFS_MAGIC,
+ BlockSize: usermem.PageSize,
+ FragmentSize: usermem.PageSize,
+ NameLength: linux.NAME_MAX,
+
+ // tmpfs currently does not support configurable size limits. In Linux,
+ // such a tmpfs mount will return f_blocks == f_bfree == f_bavail == 0 from
+ // statfs(2). However, many applications treat this as having a size limit
+ // of 0. To work around this, claim to have a very large but non-zero size,
+ // chosen to ensure that BlockSize * Blocks does not overflow int64 (which
+ // applications may also handle incorrectly).
+ // TODO(b/29637826): allow configuring a tmpfs size and enforce it.
+ Blocks: math.MaxInt64 / usermem.PageSize,
+ BlocksFree: math.MaxInt64 / usermem.PageSize,
+ BlocksAvailable: math.MaxInt64 / usermem.PageSize,
+}
+
// dentry implements vfs.DentryImpl.
type dentry struct {
vfsd vfs.Dentry
@@ -698,6 +717,11 @@ func (fd *fileDescription) SetStat(ctx context.Context, opts vfs.SetStatOptions)
return nil
}
+// StatFS implements vfs.FileDescriptionImpl.StatFS.
+func (fd *fileDescription) StatFS(ctx context.Context) (linux.Statfs, error) {
+ return globalStatfs, nil
+}
+
// Listxattr implements vfs.FileDescriptionImpl.Listxattr.
func (fd *fileDescription) Listxattr(ctx context.Context, size uint64) ([]string, error) {
return fd.inode().listxattr(size)