diff options
author | Jamie Liu <jamieliu@google.com> | 2020-08-25 16:38:07 -0700 |
---|---|---|
committer | gVisor bot <gvisor-bot@google.com> | 2020-08-25 16:40:02 -0700 |
commit | 247dcd62d436943ad0bf8455c2be22bc36da6637 (patch) | |
tree | 8b59371a081ccc1a658cc074ee786ffc1ca0b0ef | |
parent | cb573c8e0bf042ea111dc83c72f25d135623032f (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.go | 11 | ||||
-rw-r--r-- | pkg/sentry/fs/tmpfs/tmpfs.go | 12 | ||||
-rw-r--r-- | pkg/sentry/fsimpl/tmpfs/filesystem.go | 12 | ||||
-rw-r--r-- | pkg/sentry/fsimpl/tmpfs/tmpfs.go | 24 |
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) |