syscallcompat: MknodatUser: work around changed syscall.Setgroups semantics
Since go1.16beta1 (commit d1b1145cace8b968307f9311ff611e4bb810710c , https://go-review.googlesource.com/c/go/+/210639 ) syscall.{Setgroups,Setregid,Setreuid} affects all threads, which is exactly what we not want. We now use unix.{Setgroups,Setregid,Setreuid} instead. Workarounds https://github.com/golang/go/issues/1435 .
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@ -92,28 +92,38 @@ func getSupplementaryGroups(pid uint32) (gids []int) {
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}
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// OpenatUser runs the Openat syscall in the context of a different user.
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//
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// It switches the current thread to the new user, performs the syscall,
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// and switches back.
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func OpenatUser(dirfd int, path string, flags int, mode uint32, context *fuse.Context) (fd int, err error) {
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if context != nil {
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runtime.LockOSThread()
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defer runtime.UnlockOSThread()
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err = syscall.Setgroups(getSupplementaryGroups(context.Pid))
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if err != nil {
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return -1, err
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}
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defer syscall.Setgroups(nil)
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// Since go1.16beta1 (commit d1b1145cace8b968307f9311ff611e4bb810710c ,
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// https://go-review.googlesource.com/c/go/+/210639 )
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// syscall.{Setgroups,Setregid,Setreuid} affects all threads, which
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// is exactly what we not want.
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//
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// We now use unix.{Setgroups,Setregid,Setreuid} instead.
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err = syscall.Setregid(-1, int(context.Owner.Gid))
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err = unix.Setgroups(getSupplementaryGroups(context.Pid))
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if err != nil {
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return -1, err
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}
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defer syscall.Setregid(-1, 0)
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defer unix.Setgroups(nil)
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err = syscall.Setreuid(-1, int(context.Owner.Uid))
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err = unix.Setregid(-1, int(context.Owner.Gid))
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if err != nil {
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return -1, err
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}
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defer syscall.Setreuid(-1, 0)
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defer unix.Setregid(-1, 0)
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err = unix.Setreuid(-1, int(context.Owner.Uid))
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if err != nil {
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return -1, err
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}
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defer unix.Setreuid(-1, 0)
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}
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return Openat(dirfd, path, flags, mode)
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@ -125,28 +135,30 @@ func Mknodat(dirfd int, path string, mode uint32, dev int) (err error) {
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}
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// MknodatUser runs the Mknodat syscall in the context of a different user.
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//
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// See OpenatUser() for how this works.
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func MknodatUser(dirfd int, path string, mode uint32, dev int, context *fuse.Context) (err error) {
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if context != nil {
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runtime.LockOSThread()
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defer runtime.UnlockOSThread()
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err = syscall.Setgroups(getSupplementaryGroups(context.Pid))
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err = unix.Setgroups(getSupplementaryGroups(context.Pid))
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if err != nil {
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return err
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}
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defer syscall.Setgroups(nil)
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defer unix.Setgroups(nil)
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err = syscall.Setregid(-1, int(context.Owner.Gid))
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err = unix.Setregid(-1, int(context.Owner.Gid))
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if err != nil {
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return err
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}
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defer syscall.Setregid(-1, 0)
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defer unix.Setregid(-1, 0)
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err = syscall.Setreuid(-1, int(context.Owner.Uid))
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err = unix.Setreuid(-1, int(context.Owner.Uid))
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if err != nil {
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return err
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}
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defer syscall.Setreuid(-1, 0)
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defer unix.Setreuid(-1, 0)
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}
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return Mknodat(dirfd, path, mode, dev)
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@ -193,56 +205,60 @@ func FchmodatNofollow(dirfd int, path string, mode uint32) (err error) {
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}
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// SymlinkatUser runs the Symlinkat syscall in the context of a different user.
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//
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// See OpenatUser() for how this works.
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func SymlinkatUser(oldpath string, newdirfd int, newpath string, context *fuse.Context) (err error) {
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if context != nil {
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runtime.LockOSThread()
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defer runtime.UnlockOSThread()
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err = syscall.Setgroups(getSupplementaryGroups(context.Pid))
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err = unix.Setgroups(getSupplementaryGroups(context.Pid))
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if err != nil {
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return err
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}
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defer syscall.Setgroups(nil)
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defer unix.Setgroups(nil)
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err = syscall.Setregid(-1, int(context.Owner.Gid))
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err = unix.Setregid(-1, int(context.Owner.Gid))
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if err != nil {
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return err
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}
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defer syscall.Setregid(-1, 0)
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defer unix.Setregid(-1, 0)
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err = syscall.Setreuid(-1, int(context.Owner.Uid))
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err = unix.Setreuid(-1, int(context.Owner.Uid))
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if err != nil {
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return err
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}
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defer syscall.Setreuid(-1, 0)
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defer unix.Setreuid(-1, 0)
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}
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return Symlinkat(oldpath, newdirfd, newpath)
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}
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// MkdiratUser runs the Mkdirat syscall in the context of a different user.
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//
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// See OpenatUser() for how this works.
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func MkdiratUser(dirfd int, path string, mode uint32, caller *fuse.Caller) (err error) {
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if caller != nil {
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runtime.LockOSThread()
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defer runtime.UnlockOSThread()
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err = syscall.Setgroups(getSupplementaryGroups(caller.Pid))
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err = unix.Setgroups(getSupplementaryGroups(caller.Pid))
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if err != nil {
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return err
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}
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defer syscall.Setgroups(nil)
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defer unix.Setgroups(nil)
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err = syscall.Setregid(-1, int(caller.Gid))
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err = unix.Setregid(-1, int(caller.Gid))
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if err != nil {
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return err
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}
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defer syscall.Setregid(-1, 0)
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defer unix.Setregid(-1, 0)
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err = syscall.Setreuid(-1, int(caller.Uid))
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err = unix.Setreuid(-1, int(caller.Uid))
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if err != nil {
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return err
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}
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defer syscall.Setreuid(-1, 0)
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defer unix.Setreuid(-1, 0)
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}
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return Mkdirat(dirfd, path, mode)
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@ -80,7 +80,14 @@ else
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fi
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if grep -R "panic(" ./*.go internal ; then
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echo "Please use log.Panic instead of naked panic!"
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echo "$MYNAME: Please use log.Panic instead of naked panic!"
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exit 1
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fi
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# All functions from the commit msg in https://go-review.googlesource.com/c/go/+/210639
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if grep -R -E 'syscall.(Setegid|Seteuid|Setgroups|Setgid|Setregid|Setreuid|Setresgid|Setresuid|Setuid)\(' \
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./*.go internal ; then
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echo "$MYNAME: You probably want to use unix.Setgroups and friends. See the comments in OpenatUser() for why."
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exit 1
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fi
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