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-rw-r--r--pkg/sentry/fsimpl/kernfs/inode_impl_util.go33
-rw-r--r--pkg/sentry/fsimpl/tmpfs/device_file.go4
-rw-r--r--pkg/sentry/fsimpl/tmpfs/directory.go4
-rw-r--r--pkg/sentry/fsimpl/tmpfs/filesystem.go16
-rw-r--r--pkg/sentry/fsimpl/tmpfs/named_pipe.go4
-rw-r--r--pkg/sentry/fsimpl/tmpfs/regular_file.go13
-rw-r--r--pkg/sentry/fsimpl/tmpfs/socket_file.go4
-rw-r--r--pkg/sentry/fsimpl/tmpfs/symlink.go4
-rw-r--r--pkg/sentry/fsimpl/tmpfs/tmpfs.go72
-rw-r--r--pkg/sentry/vfs/permissions.go17
-rw-r--r--test/syscalls/BUILD6
-rw-r--r--test/syscalls/linux/setgid.cc15
12 files changed, 139 insertions, 53 deletions
diff --git a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
index 8139bff76..6b890a39c 100644
--- a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
+++ b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
@@ -294,22 +294,41 @@ func (a *InodeAttrs) SetStat(ctx context.Context, fs *vfs.Filesystem, creds *aut
return err
}
+ clearSID := false
stat := opts.Stat
+ if stat.Mask&linux.STATX_UID != 0 {
+ atomic.StoreUint32(&a.uid, stat.UID)
+ clearSID = true
+ }
+ if stat.Mask&linux.STATX_GID != 0 {
+ atomic.StoreUint32(&a.gid, stat.GID)
+ clearSID = true
+ }
if stat.Mask&linux.STATX_MODE != 0 {
for {
old := atomic.LoadUint32(&a.mode)
- new := old | uint32(stat.Mode & ^uint16(linux.S_IFMT))
- if swapped := atomic.CompareAndSwapUint32(&a.mode, old, new); swapped {
+ ft := old & linux.S_IFMT
+ newMode := ft | uint32(stat.Mode & ^uint16(linux.S_IFMT))
+ if clearSID {
+ newMode = vfs.ClearSUIDAndSGID(newMode)
+ }
+ if swapped := atomic.CompareAndSwapUint32(&a.mode, old, newMode); swapped {
+ clearSID = false
break
}
}
}
- if stat.Mask&linux.STATX_UID != 0 {
- atomic.StoreUint32(&a.uid, stat.UID)
- }
- if stat.Mask&linux.STATX_GID != 0 {
- atomic.StoreUint32(&a.gid, stat.GID)
+ // We may have to clear the SUID/SGID bits, but didn't do so as part of
+ // STATX_MODE.
+ if clearSID {
+ for {
+ old := atomic.LoadUint32(&a.mode)
+ newMode := vfs.ClearSUIDAndSGID(old)
+ if swapped := atomic.CompareAndSwapUint32(&a.mode, old, newMode); swapped {
+ break
+ }
+ }
}
now := ktime.NowFromContext(ctx).Nanoseconds()
diff --git a/pkg/sentry/fsimpl/tmpfs/device_file.go b/pkg/sentry/fsimpl/tmpfs/device_file.go
index 9129d35b7..616ae6730 100644
--- a/pkg/sentry/fsimpl/tmpfs/device_file.go
+++ b/pkg/sentry/fsimpl/tmpfs/device_file.go
@@ -30,7 +30,7 @@ type deviceFile struct {
minor uint32
}
-func (fs *filesystem) newDeviceFile(kuid auth.KUID, kgid auth.KGID, mode linux.FileMode, kind vfs.DeviceKind, major, minor uint32) *inode {
+func (fs *filesystem) newDeviceFile(kuid auth.KUID, kgid auth.KGID, mode linux.FileMode, kind vfs.DeviceKind, major, minor uint32, parentDir *directory) *inode {
file := &deviceFile{
kind: kind,
major: major,
@@ -44,7 +44,7 @@ func (fs *filesystem) newDeviceFile(kuid auth.KUID, kgid auth.KGID, mode linux.F
default:
panic(fmt.Sprintf("invalid DeviceKind: %v", kind))
}
- file.inode.init(file, fs, kuid, kgid, mode)
+ file.inode.init(file, fs, kuid, kgid, mode, parentDir)
file.inode.nlink = 1 // from parent directory
return &file.inode
}
diff --git a/pkg/sentry/fsimpl/tmpfs/directory.go b/pkg/sentry/fsimpl/tmpfs/directory.go
index 417ac2eff..e8d256495 100644
--- a/pkg/sentry/fsimpl/tmpfs/directory.go
+++ b/pkg/sentry/fsimpl/tmpfs/directory.go
@@ -49,9 +49,9 @@ type directory struct {
childList dentryList
}
-func (fs *filesystem) newDirectory(kuid auth.KUID, kgid auth.KGID, mode linux.FileMode) *directory {
+func (fs *filesystem) newDirectory(kuid auth.KUID, kgid auth.KGID, mode linux.FileMode, parentDir *directory) *directory {
dir := &directory{}
- dir.inode.init(dir, fs, kuid, kgid, linux.S_IFDIR|mode)
+ dir.inode.init(dir, fs, kuid, kgid, linux.S_IFDIR|mode, parentDir)
dir.inode.nlink = 2 // from "." and parent directory or ".." for root
dir.dentry.inode = &dir.inode
dir.dentry.vfsd.Init(&dir.dentry)
diff --git a/pkg/sentry/fsimpl/tmpfs/filesystem.go b/pkg/sentry/fsimpl/tmpfs/filesystem.go
index 453e41d11..4f675c21e 100644
--- a/pkg/sentry/fsimpl/tmpfs/filesystem.go
+++ b/pkg/sentry/fsimpl/tmpfs/filesystem.go
@@ -277,7 +277,7 @@ func (fs *filesystem) MkdirAt(ctx context.Context, rp *vfs.ResolvingPath, opts v
return syserror.EMLINK
}
parentDir.inode.incLinksLocked() // from child's ".."
- childDir := fs.newDirectory(creds.EffectiveKUID, creds.EffectiveKGID, opts.Mode)
+ childDir := fs.newDirectory(creds.EffectiveKUID, creds.EffectiveKGID, opts.Mode, parentDir)
parentDir.insertChildLocked(&childDir.dentry, name)
return nil
})
@@ -290,15 +290,15 @@ func (fs *filesystem) MknodAt(ctx context.Context, rp *vfs.ResolvingPath, opts v
var childInode *inode
switch opts.Mode.FileType() {
case linux.S_IFREG:
- childInode = fs.newRegularFile(creds.EffectiveKUID, creds.EffectiveKGID, opts.Mode)
+ childInode = fs.newRegularFile(creds.EffectiveKUID, creds.EffectiveKGID, opts.Mode, parentDir)
case linux.S_IFIFO:
- childInode = fs.newNamedPipe(creds.EffectiveKUID, creds.EffectiveKGID, opts.Mode)
+ childInode = fs.newNamedPipe(creds.EffectiveKUID, creds.EffectiveKGID, opts.Mode, parentDir)
case linux.S_IFBLK:
- childInode = fs.newDeviceFile(creds.EffectiveKUID, creds.EffectiveKGID, opts.Mode, vfs.BlockDevice, opts.DevMajor, opts.DevMinor)
+ childInode = fs.newDeviceFile(creds.EffectiveKUID, creds.EffectiveKGID, opts.Mode, vfs.BlockDevice, opts.DevMajor, opts.DevMinor, parentDir)
case linux.S_IFCHR:
- childInode = fs.newDeviceFile(creds.EffectiveKUID, creds.EffectiveKGID, opts.Mode, vfs.CharDevice, opts.DevMajor, opts.DevMinor)
+ childInode = fs.newDeviceFile(creds.EffectiveKUID, creds.EffectiveKGID, opts.Mode, vfs.CharDevice, opts.DevMajor, opts.DevMinor, parentDir)
case linux.S_IFSOCK:
- childInode = fs.newSocketFile(creds.EffectiveKUID, creds.EffectiveKGID, opts.Mode, opts.Endpoint)
+ childInode = fs.newSocketFile(creds.EffectiveKUID, creds.EffectiveKGID, opts.Mode, opts.Endpoint, parentDir)
default:
return syserror.EINVAL
}
@@ -387,7 +387,7 @@ afterTrailingSymlink:
defer rp.Mount().EndWrite()
// Create and open the child.
creds := rp.Credentials()
- child := fs.newDentry(fs.newRegularFile(creds.EffectiveKUID, creds.EffectiveKGID, opts.Mode))
+ child := fs.newDentry(fs.newRegularFile(creds.EffectiveKUID, creds.EffectiveKGID, opts.Mode, parentDir))
parentDir.insertChildLocked(child, name)
child.IncRef()
defer child.DecRef(ctx)
@@ -727,7 +727,7 @@ func (fs *filesystem) StatFSAt(ctx context.Context, rp *vfs.ResolvingPath) (linu
func (fs *filesystem) SymlinkAt(ctx context.Context, rp *vfs.ResolvingPath, target string) error {
return fs.doCreateAt(ctx, rp, false /* dir */, func(parentDir *directory, name string) error {
creds := rp.Credentials()
- child := fs.newDentry(fs.newSymlink(creds.EffectiveKUID, creds.EffectiveKGID, 0777, target))
+ child := fs.newDentry(fs.newSymlink(creds.EffectiveKUID, creds.EffectiveKGID, 0777, target, parentDir))
parentDir.insertChildLocked(child, name)
return nil
})
diff --git a/pkg/sentry/fsimpl/tmpfs/named_pipe.go b/pkg/sentry/fsimpl/tmpfs/named_pipe.go
index 57e7b57b0..65c2cbf86 100644
--- a/pkg/sentry/fsimpl/tmpfs/named_pipe.go
+++ b/pkg/sentry/fsimpl/tmpfs/named_pipe.go
@@ -30,9 +30,9 @@ type namedPipe struct {
// Preconditions:
// * fs.mu must be locked.
// * rp.Mount().CheckBeginWrite() has been called successfully.
-func (fs *filesystem) newNamedPipe(kuid auth.KUID, kgid auth.KGID, mode linux.FileMode) *inode {
+func (fs *filesystem) newNamedPipe(kuid auth.KUID, kgid auth.KGID, mode linux.FileMode, parentDir *directory) *inode {
file := &namedPipe{pipe: pipe.NewVFSPipe(true /* isNamed */, pipe.DefaultPipeSize)}
- file.inode.init(file, fs, kuid, kgid, linux.S_IFIFO|mode)
+ file.inode.init(file, fs, kuid, kgid, linux.S_IFIFO|mode, parentDir)
file.inode.nlink = 1 // Only the parent has a link.
return &file.inode
}
diff --git a/pkg/sentry/fsimpl/tmpfs/regular_file.go b/pkg/sentry/fsimpl/tmpfs/regular_file.go
index 82a743ff3..a6d161882 100644
--- a/pkg/sentry/fsimpl/tmpfs/regular_file.go
+++ b/pkg/sentry/fsimpl/tmpfs/regular_file.go
@@ -91,13 +91,13 @@ type regularFile struct {
size uint64
}
-func (fs *filesystem) newRegularFile(kuid auth.KUID, kgid auth.KGID, mode linux.FileMode) *inode {
+func (fs *filesystem) newRegularFile(kuid auth.KUID, kgid auth.KGID, mode linux.FileMode, parentDir *directory) *inode {
file := &regularFile{
memFile: fs.mfp.MemoryFile(),
memoryUsageKind: usage.Tmpfs,
seals: linux.F_SEAL_SEAL,
}
- file.inode.init(file, fs, kuid, kgid, linux.S_IFREG|mode)
+ file.inode.init(file, fs, kuid, kgid, linux.S_IFREG|mode, parentDir)
file.inode.nlink = 1 // from parent directory
return &file.inode
}
@@ -116,7 +116,7 @@ func newUnlinkedRegularFileDescription(ctx context.Context, creds *auth.Credenti
panic("tmpfs.newUnlinkedRegularFileDescription() called with non-tmpfs mount")
}
- inode := fs.newRegularFile(creds.EffectiveKUID, creds.EffectiveKGID, 0777)
+ inode := fs.newRegularFile(creds.EffectiveKUID, creds.EffectiveKGID, 0777, nil /* parentDir */)
d := fs.newDentry(inode)
defer d.DecRef(ctx)
d.name = name
@@ -443,6 +443,13 @@ func (fd *regularFileFD) pwrite(ctx context.Context, src usermem.IOSequence, off
rw := getRegularFileReadWriter(f, offset)
n, err := src.CopyInTo(ctx, rw)
f.inode.touchCMtimeLocked()
+ for {
+ old := atomic.LoadUint32(&f.inode.mode)
+ new := vfs.ClearSUIDAndSGID(old)
+ if swapped := atomic.CompareAndSwapUint32(&f.inode.mode, old, new); swapped {
+ break
+ }
+ }
putRegularFileReadWriter(rw)
return n, n + offset, err
}
diff --git a/pkg/sentry/fsimpl/tmpfs/socket_file.go b/pkg/sentry/fsimpl/tmpfs/socket_file.go
index 5699d5975..6112279b0 100644
--- a/pkg/sentry/fsimpl/tmpfs/socket_file.go
+++ b/pkg/sentry/fsimpl/tmpfs/socket_file.go
@@ -28,9 +28,9 @@ type socketFile struct {
ep transport.BoundEndpoint
}
-func (fs *filesystem) newSocketFile(kuid auth.KUID, kgid auth.KGID, mode linux.FileMode, ep transport.BoundEndpoint) *inode {
+func (fs *filesystem) newSocketFile(kuid auth.KUID, kgid auth.KGID, mode linux.FileMode, ep transport.BoundEndpoint, parentDir *directory) *inode {
file := &socketFile{ep: ep}
- file.inode.init(file, fs, kuid, kgid, mode)
+ file.inode.init(file, fs, kuid, kgid, mode, parentDir)
file.inode.nlink = 1 // from parent directory
return &file.inode
}
diff --git a/pkg/sentry/fsimpl/tmpfs/symlink.go b/pkg/sentry/fsimpl/tmpfs/symlink.go
index a102a2ee2..6a83296bc 100644
--- a/pkg/sentry/fsimpl/tmpfs/symlink.go
+++ b/pkg/sentry/fsimpl/tmpfs/symlink.go
@@ -25,11 +25,11 @@ type symlink struct {
target string // immutable
}
-func (fs *filesystem) newSymlink(kuid auth.KUID, kgid auth.KGID, mode linux.FileMode, target string) *inode {
+func (fs *filesystem) newSymlink(kuid auth.KUID, kgid auth.KGID, mode linux.FileMode, target string, parentDir *directory) *inode {
link := &symlink{
target: target,
}
- link.inode.init(link, fs, kuid, kgid, linux.S_IFLNK|mode)
+ link.inode.init(link, fs, kuid, kgid, linux.S_IFLNK|mode, parentDir)
link.inode.nlink = 1 // from parent directory
return &link.inode
}
diff --git a/pkg/sentry/fsimpl/tmpfs/tmpfs.go b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
index b32c54e20..a01e413e0 100644
--- a/pkg/sentry/fsimpl/tmpfs/tmpfs.go
+++ b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
@@ -190,11 +190,11 @@ func (fstype FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.Virt
var root *dentry
switch rootFileType {
case linux.S_IFREG:
- root = fs.newDentry(fs.newRegularFile(rootKUID, rootKGID, rootMode))
+ root = fs.newDentry(fs.newRegularFile(rootKUID, rootKGID, rootMode, nil /* parentDir */))
case linux.S_IFLNK:
- root = fs.newDentry(fs.newSymlink(rootKUID, rootKGID, rootMode, tmpfsOpts.RootSymlinkTarget))
+ root = fs.newDentry(fs.newSymlink(rootKUID, rootKGID, rootMode, tmpfsOpts.RootSymlinkTarget, nil /* parentDir */))
case linux.S_IFDIR:
- root = &fs.newDirectory(rootKUID, rootKGID, rootMode).dentry
+ root = &fs.newDirectory(rootKUID, rootKGID, rootMode, nil /* parentDir */).dentry
default:
fs.vfsfs.DecRef(ctx)
return nil, nil, fmt.Errorf("invalid tmpfs root file type: %#o", rootFileType)
@@ -385,10 +385,19 @@ type inode struct {
const maxLinks = math.MaxUint32
-func (i *inode) init(impl interface{}, fs *filesystem, kuid auth.KUID, kgid auth.KGID, mode linux.FileMode) {
+func (i *inode) init(impl interface{}, fs *filesystem, kuid auth.KUID, kgid auth.KGID, mode linux.FileMode, parentDir *directory) {
if mode.FileType() == 0 {
panic("file type is required in FileMode")
}
+
+ // Inherit the group and setgid bit as in fs/inode.c:inode_init_owner().
+ if parentDir != nil && parentDir.inode.mode&linux.S_ISGID == linux.S_ISGID {
+ kgid = auth.KGID(parentDir.inode.gid)
+ if mode&linux.S_IFDIR == linux.S_IFDIR {
+ mode |= linux.S_ISGID
+ }
+ }
+
i.fs = fs
i.mode = uint32(mode)
i.uid = uint32(kuid)
@@ -519,26 +528,15 @@ func (i *inode) setStat(ctx context.Context, creds *auth.Credentials, opts *vfs.
if err := vfs.CheckSetStat(ctx, creds, opts, mode, auth.KUID(atomic.LoadUint32(&i.uid)), auth.KGID(atomic.LoadUint32(&i.gid))); err != nil {
return err
}
+
i.mu.Lock()
defer i.mu.Unlock()
var (
needsMtimeBump bool
needsCtimeBump bool
)
+ clearSID := false
mask := stat.Mask
- if mask&linux.STATX_MODE != 0 {
- ft := atomic.LoadUint32(&i.mode) & linux.S_IFMT
- atomic.StoreUint32(&i.mode, ft|uint32(stat.Mode&^linux.S_IFMT))
- needsCtimeBump = true
- }
- if mask&linux.STATX_UID != 0 {
- atomic.StoreUint32(&i.uid, stat.UID)
- needsCtimeBump = true
- }
- if mask&linux.STATX_GID != 0 {
- atomic.StoreUint32(&i.gid, stat.GID)
- needsCtimeBump = true
- }
if mask&linux.STATX_SIZE != 0 {
switch impl := i.impl.(type) {
case *regularFile:
@@ -547,6 +545,7 @@ func (i *inode) setStat(ctx context.Context, creds *auth.Credentials, opts *vfs.
return err
}
if updated {
+ clearSID = true
needsMtimeBump = true
needsCtimeBump = true
}
@@ -556,6 +555,31 @@ func (i *inode) setStat(ctx context.Context, creds *auth.Credentials, opts *vfs.
return syserror.EINVAL
}
}
+ if mask&linux.STATX_UID != 0 {
+ atomic.StoreUint32(&i.uid, stat.UID)
+ needsCtimeBump = true
+ clearSID = true
+ }
+ if mask&linux.STATX_GID != 0 {
+ atomic.StoreUint32(&i.gid, stat.GID)
+ needsCtimeBump = true
+ clearSID = true
+ }
+ if mask&linux.STATX_MODE != 0 {
+ for {
+ old := atomic.LoadUint32(&i.mode)
+ ft := old & linux.S_IFMT
+ newMode := ft | uint32(stat.Mode & ^uint16(linux.S_IFMT))
+ if clearSID {
+ newMode = vfs.ClearSUIDAndSGID(newMode)
+ }
+ if swapped := atomic.CompareAndSwapUint32(&i.mode, old, newMode); swapped {
+ clearSID = false
+ break
+ }
+ }
+ needsCtimeBump = true
+ }
now := i.fs.clock.Now().Nanoseconds()
if mask&linux.STATX_ATIME != 0 {
if stat.Atime.Nsec == linux.UTIME_NOW {
@@ -584,6 +608,20 @@ func (i *inode) setStat(ctx context.Context, creds *auth.Credentials, opts *vfs.
// Ignore the ctime bump, since we just set it ourselves.
needsCtimeBump = false
}
+
+ // We may have to clear the SUID/SGID bits, but didn't do so as part of
+ // STATX_MODE.
+ if clearSID {
+ for {
+ old := atomic.LoadUint32(&i.mode)
+ newMode := vfs.ClearSUIDAndSGID(old)
+ if swapped := atomic.CompareAndSwapUint32(&i.mode, old, newMode); swapped {
+ break
+ }
+ }
+ needsCtimeBump = true
+ }
+
if needsMtimeBump {
atomic.StoreInt64(&i.mtime, now)
}
diff --git a/pkg/sentry/vfs/permissions.go b/pkg/sentry/vfs/permissions.go
index db6146fd2..b7704874f 100644
--- a/pkg/sentry/vfs/permissions.go
+++ b/pkg/sentry/vfs/permissions.go
@@ -326,3 +326,20 @@ func CheckXattrPermissions(creds *auth.Credentials, ats AccessTypes, mode linux.
}
return nil
}
+
+// ClearSUIDAndSGID clears the setuid and/or setgid bits after a chown or write.
+// Depending on the mode, neither bit, only the setuid bit, or both are cleared.
+func ClearSUIDAndSGID(mode uint32) uint32 {
+ // Directories don't have their bits changed.
+ if mode&linux.ModeDirectory == linux.ModeDirectory {
+ return mode
+ }
+
+ // Changing owners always disables the setuid bit. It disables
+ // the setgid bit when the file is executable.
+ mode &= ^uint32(linux.ModeSetUID)
+ if sgid := uint32(linux.ModeSetGID | linux.ModeGroupExec); mode&sgid == sgid {
+ mode &= ^uint32(linux.ModeSetGID)
+ }
+ return mode
+}
diff --git a/test/syscalls/BUILD b/test/syscalls/BUILD
index d6658898d..9adb1cea3 100644
--- a/test/syscalls/BUILD
+++ b/test/syscalls/BUILD
@@ -89,7 +89,7 @@ syscall_test(
size = "medium",
add_overlay = True,
test = "//test/syscalls/linux:chown_test",
- use_tmpfs = True, # chwon tests require gofer to be running as root.
+ use_tmpfs = True, # chown tests require gofer to be running as root.
)
syscall_test(
@@ -557,7 +557,11 @@ syscall_test(
)
syscall_test(
+ add_overlay = True,
test = "//test/syscalls/linux:setgid_test",
+ # setgid tests require the gofer's user namespace to have multiple groups,
+ # but bazel only provides one.
+ use_tmpfs = True,
)
syscall_test(
diff --git a/test/syscalls/linux/setgid.cc b/test/syscalls/linux/setgid.cc
index bfd91ba4f..cd030b094 100644
--- a/test/syscalls/linux/setgid.cc
+++ b/test/syscalls/linux/setgid.cc
@@ -86,7 +86,7 @@ class SetgidDirTest : public ::testing::Test {
original_gid_ = getegid();
// TODO(b/175325250): Enable when setgid directories are supported.
- SKIP_IF(IsRunningOnGvisor());
+ SKIP_IF(IsRunningWithVFS1());
SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_SETGID)));
temp_dir_ = ASSERT_NO_ERRNO_AND_VALUE(
@@ -305,9 +305,7 @@ struct FileModeTestcase {
class FileModeTest : public ::testing::TestWithParam<FileModeTestcase> {};
TEST_P(FileModeTest, WriteToFile) {
- // TODO(b/175325250): Enable when setgid directories are supported.
- SKIP_IF(IsRunningOnGvisor());
-
+ SKIP_IF(IsRunningWithVFS1());
auto temp_dir = ASSERT_NO_ERRNO_AND_VALUE(
TempPath::CreateDirWith(GetAbsoluteTestTmpdir(), 0777 /* mode */));
auto path = JoinPath(temp_dir.path(), GetParam().name);
@@ -330,9 +328,7 @@ TEST_P(FileModeTest, WriteToFile) {
}
TEST_P(FileModeTest, TruncateFile) {
- // TODO(b/175325250): Enable when setgid directories are supported.
- SKIP_IF(IsRunningOnGvisor());
-
+ SKIP_IF(IsRunningWithVFS1());
auto temp_dir = ASSERT_NO_ERRNO_AND_VALUE(
TempPath::CreateDirWith(GetAbsoluteTestTmpdir(), 0777 /* mode */));
auto path = JoinPath(temp_dir.path(), GetParam().name);
@@ -343,6 +339,11 @@ TEST_P(FileModeTest, TruncateFile) {
ASSERT_THAT(fstat(fd.get(), &stats), SyscallSucceeds());
EXPECT_EQ(stats.st_mode & kDirmodeMask, GetParam().mode);
+ // Write something to the file, as truncating an empty file is a no-op.
+ constexpr char c = 'M';
+ ASSERT_THAT(write(fd.get(), &c, sizeof(c)),
+ SyscallSucceedsWithValue(sizeof(c)));
+
// For security reasons, truncating the file clears the SUID bit, and clears
// the SGID bit when the group executable bit is unset (which is not a true
// SGID binary).
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-01 16:23:13 +0000