From 02c91d73ce2c63f999f2c29cf61d55caef19c67b Mon Sep 17 00:00:00 2001 From: Jakob Unterwurzacher Date: Thu, 19 Aug 2021 09:01:58 +0200 Subject: [PATCH] syscallcompat: use early return in asUser() --- internal/syscallcompat/sys_linux.go | 63 ++++++++++++++++------------- 1 file changed, 34 insertions(+), 29 deletions(-) diff --git a/internal/syscallcompat/sys_linux.go b/internal/syscallcompat/sys_linux.go index 9672be7..a1d7d40 100644 --- a/internal/syscallcompat/sys_linux.go +++ b/internal/syscallcompat/sys_linux.go @@ -91,38 +91,43 @@ func getSupplementaryGroups(pid uint32) (gids []int) { return nil } -// asUser runs the function `f` under the effective uid, gid, groups specified +// asUser runs `f()` under the effective uid, gid, groups specified // in `context`. +// +// If `context` is nil, `f()` is executed directly without switching user id. func asUser(f func() (int, error), context *fuse.Context) (int, error) { - if context != nil { - runtime.LockOSThread() - defer runtime.UnlockOSThread() - - // 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. - - err := unix.Setgroups(getSupplementaryGroups(context.Pid)) - if err != nil { - return -1, err - } - defer unix.Setgroups(nil) - - err = unix.Setregid(-1, int(context.Owner.Gid)) - if err != nil { - return -1, err - } - defer unix.Setregid(-1, 0) - - err = unix.Setreuid(-1, int(context.Owner.Uid)) - if err != nil { - return -1, err - } - defer unix.Setreuid(-1, 0) + if context == nil { + return f() } + + runtime.LockOSThread() + defer runtime.UnlockOSThread() + + // 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. + + err := unix.Setgroups(getSupplementaryGroups(context.Pid)) + if err != nil { + return -1, err + } + defer unix.Setgroups(nil) + + err = unix.Setregid(-1, int(context.Owner.Gid)) + if err != nil { + return -1, err + } + defer unix.Setregid(-1, 0) + + err = unix.Setreuid(-1, int(context.Owner.Uid)) + if err != nil { + return -1, err + } + defer unix.Setreuid(-1, 0) + return f() }