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syscall: support Faccessat flags argument

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The Linux kernel faccessat system call does not take a flags parameter.
The flag parameter to the C library faccessat function is implemented in C.
The syscall.Faccessat function takes a flags parameter. In older releases
we have passed the flags parameter to the kernel, which ignored it.
In CL 120015 we started returning an error if any flags were set.
That seems clearly better than ignoring them, but it turns out that some
code was using the flags. The code was previously subtly broken.
Now it is obviously broken. That is better, but we can do better still:
we can implement the flags as the C library does. That is what this CL does.

Change-Id: I259bd6f240c3951e939b81c3032dead3d9c567b4
Reviewed-on: https://go-review.googlesource.com/126415
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Ian Lance Taylor 2018-07-27 10:48:18 -07:00
parent 902fc11427
commit d970519086
19 changed files with 252 additions and 11 deletions
Download patch file Download diff file Expand all files Collapse all files

64
src/syscall/syscall_linux.go
View file

@ -40,12 +40,72 @@ func Creat(path string, mode uint32) (fd int, err error) {
func Faccessat(dirfd int, path string, mode uint32, flags int) (err error) {
if flags & ^(_AT_SYMLINK_NOFOLLOW|_AT_EACCESS) != 0 {
return EINVAL
} else if flags&(_AT_SYMLINK_NOFOLLOW|_AT_EACCESS) != 0 {
return EOPNOTSUPP
}
// The Linux kernel faccessat system call does not take any flags.
// The glibc faccessat implements the flags itself; see
// https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/faccessat.c;hb=HEAD
// Because people naturally expect syscall.Faccessat to act
// like C faccessat, we do the same.
if flags == 0 {
return faccessat(dirfd, path, mode)
}
var st Stat_t
if err := fstatat(dirfd, path, &st, flags&_AT_SYMLINK_NOFOLLOW); err != nil {
return err
}
mode &= 7
if mode == 0 {
return nil
}
var uid int
if flags&_AT_EACCESS != 0 {
uid = Geteuid()
} else {
uid = Getuid()
}
if uid == 0 {
if mode&1 == 0 {
// Root can read and write any file.
return nil
}
if st.Mode&0111 != 0 {
// Root can execute any file that anybody can execute.
return nil
}
return EACCES
}
var fmode uint32
if uint32(uid) == st.Uid {
fmode = (st.Mode >> 6) & 7
} else {
var gid int
if flags&_AT_EACCESS != 0 {
gid = Getegid()
} else {
gid = Getgid()
}
if uint32(gid) == st.Gid {
fmode = (st.Mode >> 3) & 7
} else {
fmode = st.Mode & 7
}
}
if fmode&mode == mode {
return nil
}
return EACCES
}
//sys fchmodat(dirfd int, path string, mode uint32) (err error)
func Fchmodat(dirfd int, path string, mode uint32, flags int) (err error) {

1
src/syscall/syscall_linux_386.go
View file

@ -53,6 +53,7 @@ func Pipe2(p []int, flags int) (err error) {
//sys Dup2(oldfd int, newfd int) (err error)
//sys Fchown(fd int, uid int, gid int) (err error) = SYS_FCHOWN32
//sys Fstat(fd int, stat *Stat_t) (err error) = SYS_FSTAT64
//sys fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) = SYS_FSTATAT64
//sys Ftruncate(fd int, length int64) (err error) = SYS_FTRUNCATE64
//sysnb Getegid() (egid int) = SYS_GETEGID32
//sysnb Geteuid() (euid int) = SYS_GETEUID32

1
src/syscall/syscall_linux_arm.go
View file

@ -77,6 +77,7 @@ func Seek(fd int, offset int64, whence int) (newoffset int64, err error) {
//sys Dup2(oldfd int, newfd int) (err error)
//sys Fchown(fd int, uid int, gid int) (err error) = SYS_FCHOWN32
//sys Fstat(fd int, stat *Stat_t) (err error) = SYS_FSTAT64
//sys fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) = SYS_FSTATAT64
//sysnb Getegid() (egid int) = SYS_GETEGID32
//sysnb Geteuid() (euid int) = SYS_GETEUID32
//sysnb Getgid() (gid int) = SYS_GETGID32

1
src/syscall/syscall_linux_arm64.go
View file

@ -13,6 +13,7 @@ const (
//sys Fchown(fd int, uid int, gid int) (err error)
//sys Fstat(fd int, stat *Stat_t) (err error)
//sys Fstatat(fd int, path string, stat *Stat_t, flags int) (err error)
//sys fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error)
//sys Fstatfs(fd int, buf *Statfs_t) (err error)
//sys Ftruncate(fd int, length int64) (err error)
//sysnb Getegid() (egid int)

1
src/syscall/syscall_linux_mips64x.go
View file

@ -15,6 +15,7 @@ const (
//sys Dup2(oldfd int, newfd int) (err error)
//sys Fchown(fd int, uid int, gid int) (err error)
//sys Fstatfs(fd int, buf *Statfs_t) (err error)
//sys fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) = SYS_NEWFSTATAT
//sys Ftruncate(fd int, length int64) (err error)
//sysnb Getegid() (egid int)
//sysnb Geteuid() (euid int)

1
src/syscall/syscall_linux_mipsx.go
View file

@ -18,6 +18,7 @@ func Syscall9(trap, a1, a2, a3, a4, a5, a6, a7, a8, a9 uintptr) (r1, r2 uintptr,
//sys Dup2(oldfd int, newfd int) (err error)
//sys Fchown(fd int, uid int, gid int) (err error)
//sys fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) = SYS_FSTATAT64
//sys Ftruncate(fd int, length int64) (err error) = SYS_FTRUNCATE64
//sysnb Getegid() (egid int)
//sysnb Geteuid() (euid int)

1
src/syscall/syscall_linux_ppc64x.go
View file

@ -15,6 +15,7 @@ const (
//sys Dup2(oldfd int, newfd int) (err error)
//sys Fchown(fd int, uid int, gid int) (err error)
//sys Fstat(fd int, stat *Stat_t) (err error)
//sys fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) = SYS_NEWFSTATAT
//sys Fstatfs(fd int, buf *Statfs_t) (err error)
//sys Ftruncate(fd int, length int64) (err error)
//sysnb Getegid() (egid int)

1
src/syscall/syscall_linux_s390x.go
View file

@ -14,6 +14,7 @@ const (
//sys Dup2(oldfd int, newfd int) (err error)
//sys Fchown(fd int, uid int, gid int) (err error)
//sys Fstat(fd int, stat *Stat_t) (err error)
//sys fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) = SYS_NEWFSTATAT
//sys Fstatfs(fd int, buf *Statfs_t) (err error)
//sys Ftruncate(fd int, length int64) (err error)
//sysnb Getegid() (egid int)

40
src/syscall/syscall_linux_test.go
View file

@ -57,25 +57,27 @@ const (
_AT_SYMLINK_NOFOLLOW = 0x100
_AT_FDCWD = -0x64
_AT_EACCESS = 0x200
_F_OK = 0
_R_OK = 4
)
func TestFaccessat(t *testing.T) {
defer chtmpdir(t)()
touch(t, "file1")
err := syscall.Faccessat(_AT_FDCWD, "file1", syscall.O_RDONLY, 0)
err := syscall.Faccessat(_AT_FDCWD, "file1", _R_OK, 0)
if err != nil {
t.Errorf("Faccessat: unexpected error: %v", err)
}
err = syscall.Faccessat(_AT_FDCWD, "file1", syscall.O_RDONLY, 2)
err = syscall.Faccessat(_AT_FDCWD, "file1", _R_OK, 2)
if err != syscall.EINVAL {
t.Errorf("Faccessat: unexpected error: %v, want EINVAL", err)
}
err = syscall.Faccessat(_AT_FDCWD, "file1", syscall.O_RDONLY, _AT_EACCESS)
if err != syscall.EOPNOTSUPP {
t.Errorf("Faccessat: unexpected error: %v, want EOPNOTSUPP", err)
err = syscall.Faccessat(_AT_FDCWD, "file1", _R_OK, _AT_EACCESS)
if err != nil {
t.Errorf("Faccessat: unexpected error: %v", err)
}
err = os.Symlink("file1", "symlink1")
@ -83,9 +85,31 @@ func TestFaccessat(t *testing.T) {
t.Fatal(err)
}
err = syscall.Faccessat(_AT_FDCWD, "symlink1", syscall.O_RDONLY, _AT_SYMLINK_NOFOLLOW)
if err != syscall.EOPNOTSUPP {
t.Errorf("Faccessat: unexpected error: %v, want EOPNOTSUPP", err)
err = syscall.Faccessat(_AT_FDCWD, "symlink1", _R_OK, _AT_SYMLINK_NOFOLLOW)
if err != nil {
t.Errorf("Faccessat SYMLINK_NOFOLLOW: unexpected error %v", err)
}
// We can't really test _AT_SYMLINK_NOFOLLOW, because there
// doesn't seem to be any way to change the mode of a symlink.
// We don't test _AT_EACCESS because such tests are only
// meaningful if run as root.
err = syscall.Fchmodat(_AT_FDCWD, "file1", 0, 0)
if err != nil {
t.Errorf("Fchmodat: unexpected error %v", err)
}
err = syscall.Faccessat(_AT_FDCWD, "file1", _F_OK, _AT_SYMLINK_NOFOLLOW)
if err != nil {
t.Errorf("Faccessat: unexpected error: %v", err)
}
err = syscall.Faccessat(_AT_FDCWD, "file1", _R_OK, _AT_SYMLINK_NOFOLLOW)
if err != syscall.EACCES {
if syscall.Getuid() != 0 {
t.Errorf("Faccessat: unexpected error: %v, want EACCES", err)
}
}
}

15
src/syscall/zsyscall_linux_386.go
View file

@ -1188,6 +1188,21 @@ func Fstat(fd int, stat *Stat_t) (err error) {
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) {
var _p0 *byte
_p0, err = BytePtrFromString(path)
if err != nil {
return
}
_, _, e1 := Syscall6(SYS_FSTATAT64, uintptr(dirfd), uintptr(unsafe.Pointer(_p0)), uintptr(unsafe.Pointer(stat)), uintptr(flags), 0, 0)
if e1 != 0 {
err = errnoErr(e1)
}
return
}
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func Ftruncate(fd int, length int64) (err error) {
_, _, e1 := Syscall(SYS_FTRUNCATE64, uintptr(fd), uintptr(length), uintptr(length>>32))
if e1 != 0 {

15
src/syscall/zsyscall_linux_arm.go
View file

@ -1357,6 +1357,21 @@ func Fstat(fd int, stat *Stat_t) (err error) {
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) {
var _p0 *byte
_p0, err = BytePtrFromString(path)
if err != nil {
return
}
_, _, e1 := Syscall6(SYS_FSTATAT64, uintptr(dirfd), uintptr(unsafe.Pointer(_p0)), uintptr(unsafe.Pointer(stat)), uintptr(flags), 0, 0)
if e1 != 0 {
err = errnoErr(e1)
}
return
}
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func Getegid() (egid int) {
r0, _ := rawSyscallNoError(SYS_GETEGID32, 0, 0, 0)
egid = int(r0)

15
src/syscall/zsyscall_linux_arm64.go
View file

@ -1190,6 +1190,21 @@ func Fstatat(fd int, path string, stat *Stat_t, flags int) (err error) {
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) {
var _p0 *byte
_p0, err = BytePtrFromString(path)
if err != nil {
return
}
_, _, e1 := Syscall6(SYS_FSTATAT, uintptr(dirfd), uintptr(unsafe.Pointer(_p0)), uintptr(unsafe.Pointer(stat)), uintptr(flags), 0, 0)
if e1 != 0 {
err = errnoErr(e1)
}
return
}
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func Fstatfs(fd int, buf *Statfs_t) (err error) {
_, _, e1 := Syscall(SYS_FSTATFS, uintptr(fd), uintptr(unsafe.Pointer(buf)), 0)
if e1 != 0 {

15
src/syscall/zsyscall_linux_mips.go
View file

@ -1158,6 +1158,21 @@ func Fchown(fd int, uid int, gid int) (err error) {
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) {
var _p0 *byte
_p0, err = BytePtrFromString(path)
if err != nil {
return
}
_, _, e1 := Syscall6(SYS_FSTATAT64, uintptr(dirfd), uintptr(unsafe.Pointer(_p0)), uintptr(unsafe.Pointer(stat)), uintptr(flags), 0, 0)
if e1 != 0 {
err = errnoErr(e1)
}
return
}
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func Ftruncate(fd int, length int64) (err error) {
_, _, e1 := Syscall6(SYS_FTRUNCATE64, uintptr(fd), 0, uintptr(length>>32), uintptr(length), 0, 0)
if e1 != 0 {

15
src/syscall/zsyscall_linux_mips64.go
View file

@ -1168,6 +1168,21 @@ func Fstatfs(fd int, buf *Statfs_t) (err error) {
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) {
var _p0 *byte
_p0, err = BytePtrFromString(path)
if err != nil {
return
}
_, _, e1 := Syscall6(SYS_NEWFSTATAT, uintptr(dirfd), uintptr(unsafe.Pointer(_p0)), uintptr(unsafe.Pointer(stat)), uintptr(flags), 0, 0)
if e1 != 0 {
err = errnoErr(e1)
}
return
}
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func Ftruncate(fd int, length int64) (err error) {
_, _, e1 := Syscall(SYS_FTRUNCATE, uintptr(fd), uintptr(length), 0)
if e1 != 0 {

15
src/syscall/zsyscall_linux_mips64le.go
View file

@ -1168,6 +1168,21 @@ func Fstatfs(fd int, buf *Statfs_t) (err error) {
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) {
var _p0 *byte
_p0, err = BytePtrFromString(path)
if err != nil {
return
}
_, _, e1 := Syscall6(SYS_NEWFSTATAT, uintptr(dirfd), uintptr(unsafe.Pointer(_p0)), uintptr(unsafe.Pointer(stat)), uintptr(flags), 0, 0)
if e1 != 0 {
err = errnoErr(e1)
}
return
}
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func Ftruncate(fd int, length int64) (err error) {
_, _, e1 := Syscall(SYS_FTRUNCATE, uintptr(fd), uintptr(length), 0)
if e1 != 0 {

15
src/syscall/zsyscall_linux_mipsle.go
View file

@ -1158,6 +1158,21 @@ func Fchown(fd int, uid int, gid int) (err error) {
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) {
var _p0 *byte
_p0, err = BytePtrFromString(path)
if err != nil {
return
}
_, _, e1 := Syscall6(SYS_FSTATAT64, uintptr(dirfd), uintptr(unsafe.Pointer(_p0)), uintptr(unsafe.Pointer(stat)), uintptr(flags), 0, 0)
if e1 != 0 {
err = errnoErr(e1)
}
return
}
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func Ftruncate(fd int, length int64) (err error) {
_, _, e1 := Syscall6(SYS_FTRUNCATE64, uintptr(fd), 0, uintptr(length), uintptr(length>>32), 0, 0)
if e1 != 0 {

15
src/syscall/zsyscall_linux_ppc64.go
View file

@ -1168,6 +1168,21 @@ func Fstat(fd int, stat *Stat_t) (err error) {
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) {
var _p0 *byte
_p0, err = BytePtrFromString(path)
if err != nil {
return
}
_, _, e1 := Syscall6(SYS_NEWFSTATAT, uintptr(dirfd), uintptr(unsafe.Pointer(_p0)), uintptr(unsafe.Pointer(stat)), uintptr(flags), 0, 0)
if e1 != 0 {
err = errnoErr(e1)
}
return
}
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func Fstatfs(fd int, buf *Statfs_t) (err error) {
_, _, e1 := Syscall(SYS_FSTATFS, uintptr(fd), uintptr(unsafe.Pointer(buf)), 0)
if e1 != 0 {

15
src/syscall/zsyscall_linux_ppc64le.go
View file

@ -1168,6 +1168,21 @@ func Fstat(fd int, stat *Stat_t) (err error) {
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) {
var _p0 *byte
_p0, err = BytePtrFromString(path)
if err != nil {
return
}
_, _, e1 := Syscall6(SYS_NEWFSTATAT, uintptr(dirfd), uintptr(unsafe.Pointer(_p0)), uintptr(unsafe.Pointer(stat)), uintptr(flags), 0, 0)
if e1 != 0 {
err = errnoErr(e1)
}
return
}
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func Fstatfs(fd int, buf *Statfs_t) (err error) {
_, _, e1 := Syscall(SYS_FSTATFS, uintptr(fd), uintptr(unsafe.Pointer(buf)), 0)
if e1 != 0 {

15
src/syscall/zsyscall_linux_s390x.go
View file

@ -1168,6 +1168,21 @@ func Fstat(fd int, stat *Stat_t) (err error) {
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) {
var _p0 *byte
_p0, err = BytePtrFromString(path)
if err != nil {
return
}
_, _, e1 := Syscall6(SYS_NEWFSTATAT, uintptr(dirfd), uintptr(unsafe.Pointer(_p0)), uintptr(unsafe.Pointer(stat)), uintptr(flags), 0, 0)
if e1 != 0 {
err = errnoErr(e1)
}
return
}
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
func Fstatfs(fd int, buf *Statfs_t) (err error) {
_, _, e1 := Syscall(SYS_FSTATFS, uintptr(fd), uintptr(unsafe.Pointer(buf)), 0)
if e1 != 0 {