From a868c2b7b759c19388f6c3f0be1dba040bf42c35 Mon Sep 17 00:00:00 2001 From: Kir Kolyshkin Date: Mon, 27 Feb 2023 15:40:38 -0800 Subject: [PATCH] Fix runc run "permission denied" when rootless Since commit 957d97bcf43f41beef96 was made to fix issue [7], a few things happened: - a similar functionality appeared in go 1.20 [1], so the issue mentioned in the comment (being removed) is no longer true; - a bug in runc was found [2], which also affects go [3]; - the bug was fixed in go 1.21 [4] and 1.20.2 [5]; - a similar fix was made to x/sys/unix.Faccessat [6]. The essense of [2] is, even if a (non-root) user that the container is run as does not have execute permission bit set for the executable, it should still work in case runc has the CAP_DAC_OVERRIDE capability set. To fix this [2] without reintroducing the older bug [7]: - drop own Eaccess implementation; - use the one from x/sys/unix for Go 1.19 (depends on [6]); - do not use anything when Go 1.20+ is used. NOTE it is virtually impossible to fix the bug [2] when Go 1.20 or Go 1.20.1 is used because of [3]. A test case is added by a separate commit. Fixes: #3715. [1] https://go-review.googlesource.com/c/go/+/414824 [2] https://github.com/opencontainers/runc/issues/3715 [3] https://go.dev/issue/58552 [4] https://go-review.googlesource.com/c/go/+/468735 [5] https://go-review.googlesource.com/c/go/+/469956 [6] https://go-review.googlesource.com/c/sys/+/468877 [7] https://github.com/opencontainers/runc/issues/3520 Signed-off-by: Kir Kolyshkin (cherry picked from commit 8491d33482a4cfd37bad86b75a02c8f63464f427) Signed-off-by: Kir Kolyshkin --- libcontainer/system/linux.go | 19 ------------------- 1 file changed, 19 deletions(-) diff --git a/libcontainer/system/linux.go b/libcontainer/system/linux.go index 039059a44..e1d6eb180 100644 --- a/libcontainer/system/linux.go +++ b/libcontainer/system/linux.go @@ -31,25 +31,6 @@ func (p ParentDeathSignal) Set() error { return SetParentDeathSignal(uintptr(p)) } -// Eaccess is similar to unix.Access except for setuid/setgid binaries -// it checks against the effective (rather than real) uid and gid. -func Eaccess(path string) error { - err := unix.Faccessat2(unix.AT_FDCWD, path, unix.X_OK, unix.AT_EACCESS) - if err != unix.ENOSYS && err != unix.EPERM { //nolint:errorlint // unix errors are bare - return err - } - - // Faccessat2() not available; check if we are a set[ug]id binary. - if os.Getuid() == os.Geteuid() && os.Getgid() == os.Getegid() { - // For a non-set[ug]id binary, use access(2). - return unix.Access(path, unix.X_OK) - } - - // For a setuid/setgid binary, there is no fallback way - // so assume we can execute the binary. - return nil -} - func Execv(cmd string, args []string, env []string) error { name, err := exec.LookPath(cmd) if err != nil {