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syscallcompat: Fix syscall emulation for absolute paths 

For absolute paths, the file descriptor should be ignored. In such a case
there is also no need to hold the lock or change the working directory.
This commit is contained in:
Sebastian Lackner 2017-11-30 21:13:46 +01:00 committed by rfjakob
parent 9bcde0c09e
commit f30522a0c1
2 changed files with 141 additions and 55 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

120
internal/syscallcompat/emulate.go
View File

@ -64,18 +64,20 @@ func emulateRenameat(olddirfd int, oldpath string, newdirfd int, newpath string)
// emulateUnlinkat emulates the syscall for platforms that don't have it
// in the kernel (darwin).
func emulateUnlinkat(dirfd int, path string, flags int) (err error) {
chdirMutex.Lock()
defer chdirMutex.Unlock()
cwd, err := syscall.Open(".", syscall.O_RDONLY, 0)
if err != nil {
return err
if !filepath.IsAbs(path) {
chdirMutex.Lock()
defer chdirMutex.Unlock()
cwd, err := syscall.Open(".", syscall.O_RDONLY, 0)
if err != nil {
return err
}
defer syscall.Close(cwd)
err = syscall.Fchdir(dirfd)
if err != nil {
return err
}
defer syscall.Fchdir(cwd)
}
defer syscall.Close(cwd)
err = syscall.Fchdir(dirfd)
if err != nil {
return err
}
defer syscall.Fchdir(cwd)
if (flags & unix.AT_REMOVEDIR) != 0 {
return syscall.Rmdir(path)
} else {
@ -123,18 +125,20 @@ func dirfdAbs(dirfd int, path string) (string, error) {
// emulateFchmodat emulates the syscall for platforms that don't have it
// in the kernel (darwin).
func emulateFchmodat(dirfd int, path string, mode uint32, flags int) (err error) {
chdirMutex.Lock()
defer chdirMutex.Unlock()
cwd, err := syscall.Open(".", syscall.O_RDONLY, 0)
if err != nil {
return err
if !filepath.IsAbs(path) {
chdirMutex.Lock()
defer chdirMutex.Unlock()
cwd, err := syscall.Open(".", syscall.O_RDONLY, 0)
if err != nil {
return err
}
defer syscall.Close(cwd)
err = syscall.Fchdir(dirfd)
if err != nil {
return err
}
defer syscall.Fchdir(cwd)
}
defer syscall.Close(cwd)
err = syscall.Fchdir(dirfd)
if err != nil {
return err
}
defer syscall.Fchdir(cwd)
// We also don't have Lchmod, so emulate it (poorly).
if flags&unix.AT_SYMLINK_NOFOLLOW != 0 {
fi, err := os.Lstat(path)
@ -151,53 +155,59 @@ func emulateFchmodat(dirfd int, path string, mode uint32, flags int) (err error)
// emulateFchownat emulates the syscall for platforms that don't have it
// in the kernel (darwin).
func emulateFchownat(dirfd int, path string, uid int, gid int, flags int) (err error) {
chdirMutex.Lock()
defer chdirMutex.Unlock()
cwd, err := syscall.Open(".", syscall.O_RDONLY, 0)
if err != nil {
return err
if !filepath.IsAbs(path) {
chdirMutex.Lock()
defer chdirMutex.Unlock()
cwd, err := syscall.Open(".", syscall.O_RDONLY, 0)
if err != nil {
return err
}
defer syscall.Close(cwd)
err = syscall.Fchdir(dirfd)
if err != nil {
return err
}
defer syscall.Fchdir(cwd)
}
defer syscall.Close(cwd)
err = syscall.Fchdir(dirfd)
if err != nil {
return err
}
defer syscall.Fchdir(cwd)
return syscall.Lchown(path, uid, gid)
}
// emulateSymlinkat emulates the syscall for platforms that don't have it
// in the kernel (darwin).
func emulateSymlinkat(oldpath string, newdirfd int, newpath string) (err error) {
chdirMutex.Lock()
defer chdirMutex.Unlock()
cwd, err := syscall.Open(".", syscall.O_RDONLY, 0)
if err != nil {
return err
if !filepath.IsAbs(newpath) {
chdirMutex.Lock()
defer chdirMutex.Unlock()
cwd, err := syscall.Open(".", syscall.O_RDONLY, 0)
if err != nil {
return err
}
defer syscall.Close(cwd)
err = syscall.Fchdir(newdirfd)
if err != nil {
return err
}
defer syscall.Fchdir(cwd)
}
defer syscall.Close(cwd)
err = syscall.Fchdir(newdirfd)
if err != nil {
return err
}
defer syscall.Fchdir(cwd)
return syscall.Symlink(oldpath, newpath)
}
// emulateMkdirat emulates the syscall for platforms that don't have it
// in the kernel (darwin).
func emulateMkdirat(dirfd int, path string, mode uint32) (err error) {
chdirMutex.Lock()
defer chdirMutex.Unlock()
cwd, err := syscall.Open(".", syscall.O_RDONLY, 0)
if err != nil {
return err
if !filepath.IsAbs(path) {
chdirMutex.Lock()
defer chdirMutex.Unlock()
cwd, err := syscall.Open(".", syscall.O_RDONLY, 0)
if err != nil {
return err
}
defer syscall.Close(cwd)
err = syscall.Fchdir(dirfd)
if err != nil {
return err
}
defer syscall.Fchdir(cwd)
}
defer syscall.Close(cwd)
err = syscall.Fchdir(dirfd)
if err != nil {
return err
}
defer syscall.Fchdir(cwd)
return syscall.Mkdir(path, mode)
}

76
internal/syscallcompat/emulate_test.go
View File

@ -67,6 +67,15 @@ func TestEmulateOpenat(t *testing.T) {
if rawFd < 0 {
t.Fatalf("rawFd=%d", rawFd)
}
// Test with absolute path
rawFd, err = emulateOpenat(-1, tmpDir + "/testOpenAt", 0, 0)
if err != nil {
t.Fatal(err)
}
defer syscall.Close(rawFd)
if rawFd < 0 {
t.Fatalf("rawFd=%d", rawFd)
}
}
func TestEmulateRenameat(t *testing.T) {
@ -95,6 +104,15 @@ func TestEmulateRenameat(t *testing.T) {
if err != nil {
t.Fatal(err)
}
// Test with absolute path
err = emulateRenameat(-1, tmpDir + "/dir2/f2", -1, tmpDir + "/dir2/f1")
if err != nil {
t.Fatal(err)
}
_, err = os.Stat(tmpDir + "/dir2/f1")
if err != nil {
t.Fatal(err)
}
}
func TestEmulateUnlinkat(t *testing.T) {
@ -135,6 +153,19 @@ func TestEmulateUnlinkat(t *testing.T) {
if err == nil {
t.Fatalf("dir not deleted!")
}
// Test with absolute path
err = os.Mkdir(tmpDir + "/unlink1/d1", 0700)
if err != nil {
t.Fatal(err)
}
err = emulateUnlinkat(-1, tmpDir + "/unlink1/d1", unix.AT_REMOVEDIR)
if err != nil {
t.Fatal(err)
}
_, err = os.Stat(tmpDir + "/unlink1/d1")
if err == nil {
t.Fatalf("dir not deleted!")
}
}
func TestEmulateMknodat(t *testing.T) {
@ -146,6 +177,15 @@ func TestEmulateMknodat(t *testing.T) {
if err != nil {
t.Fatal(err)
}
// Test with absolute path
err = emulateMknodat(-1, tmpDir + "/fifo2", unix.S_IFIFO, 0)
if err != nil {
t.Fatal(err)
}
_, err = os.Stat(tmpDir + "/fifo2")
if err != nil {
t.Fatal(err)
}
}
func TestEmulateFchmodat(t *testing.T) {
@ -187,6 +227,18 @@ func TestEmulateFchmodat(t *testing.T) {
if st.Mode != 0100600 {
t.Fatalf("Wrong mode: have %o, want %o", st.Mode, 0100600)
}
// Test with absolute path
err = emulateFchmodat(-1, tmpDir + "/chmod", 0400, 0)
if err != nil {
t.Fatal(err)
}
err = syscall.Lstat(tmpDir + "/chmod", &st)
if err != nil {
t.Fatal(err)
}
if st.Mode != 0100400 {
t.Fatalf("Wrong mode: have %o, want %o", st.Mode, 0100400)
}
}
func TestEmulateFchownat(t *testing.T) {
@ -206,6 +258,18 @@ func TestEmulateSymlinkat(t *testing.T) {
if st.Mode != 0120777 {
t.Fatalf("Wrong mode, have %o, want 0120777", st.Mode)
}
// Test with absolute path
err = emulateSymlinkat("/foo/bar/baz", -1, tmpDir + "/symlink2")
if err != nil {
t.Fatal(err)
}
err = syscall.Lstat(tmpDir + "/symlink2", &st)
if err != nil {
t.Fatal(err)
}
if st.Mode != 0120777 {
t.Fatalf("Wrong mode, have %o, want 0120777", st.Mode)
}
}
func TestEmulateMkdirat(t *testing.T) {
@ -220,4 +284,16 @@ func TestEmulateMkdirat(t *testing.T) {
if !fi.IsDir() {
t.Fatalf("mkdirat did not create a directory")
}
// Test with absolute path
err = emulateMkdirat(-1, tmpDir + "/mkdirat2", 0100)
if err != nil {
t.Fatal(err)
}
fi, err = os.Stat(tmpDir + "/mkdirat2")
if err != nil {
t.Fatal(err)
}
if !fi.IsDir() {
t.Fatalf("mkdirat did not create a directory")
}
}