diff options
| -rwxr-xr-x | tmpoverlay | 89 |
1 files changed, 58 insertions, 31 deletions
@@ -20,13 +20,17 @@ examples: tmpoverlay / /new_root # make a thin copy of root tmpoverlay /etc # make read-only /etc writable tmpoverlay /a /b /c /merged # merge /a, /b, /c, and a fresh tmpfs + tmpoverlay / # USE WITH CAUTION, see docs EOF } log() { fmt=$1 shift - printf "tmpoverlay: $fmt\n" "$@" >&2 + printf 'tmpoverlay: ' >&2 + # shellcheck disable=SC2059 + printf "$fmt" "$@" >&2 + printf '\n' >&2 } logv() { @@ -35,6 +39,12 @@ logv() { fi } +cmdv() { + logv '%s ' "$@" + "$@" +} + +unset own_tmpdir die() { r=$? trap - INT TERM QUIT @@ -48,14 +58,15 @@ die() { if [ -d "$tmpdir" ] && [ -n "$own_tmpdir" ]; then if mountpoint -q "$tmpdir"; then logv 'unmounting tmpdir' + # shellcheck disable=SC2086 umount $no_mtab "$tmpdir" fi logv 'deleting tmpdir' rmdir "$tmpdir" fi if [ -n "$sig" ]; then - logv 'reraising SIG%s' $1 - kill -$1 $$ && read _ + logv 'reraising SIG%s' "$1" + kill "-$1" "$$" && read -r _ fi logv 'exiting' if [ $r = 0 ]; then @@ -87,8 +98,6 @@ my_getopt() { "$@" } -unset own_tmpdir - args=$(my_getopt "$@") || { usage >&2; exit 1; } eval set -- "$args" unset args @@ -148,38 +157,56 @@ mount -t tmpfs ${tmpfs_opts:+-o "$tmpfs_opts"} ${verbose:+-v} tmpfs "$tmpdir" || upperdir="$tmpdir/upper" workdir="$tmpdir/work" -testdir="$tmpdir/test" tmpmnt="$tmpdir/tmpmnt" logv 'creating dirs' -mkdir "$upperdir" "$workdir" "$testdir" "$tmpmnt" || die +mkdir "$upperdir" "$workdir" "$tmpmnt" || die -our_ovl_opts= -test_ovl_opts="lowerdir=$testdir,upperdir=$upperdir,workdir=$workdir" +ovl_opts="lowerdir=$lowerdir,upperdir=$upperdir,workdir=$workdir" logv 'testing overlay options' -mount -n -t overlay -o "$test_ovl_opts" overlay "$tmpmnt" || die "overlayfs is not supported" +mount -n -t overlay -o "$ovl_opts" overlay "$tmpmnt" || die "overlayfs is not supported" umount "$tmpmnt" if [ -n "$extra_ovl_opts" ]; then - mount -n -t overlay -o "$test_ovl_opts$extra_ovl_opts" overlay "$tmpmnt" || die "invalid extra overlayfs options" + ovl_opts="$ovl_opts,$extra_ovl_opts" + mount -n -t overlay -o "$ovl_opts" overlay "$tmpmnt" || die "invalid extra overlayfs options" umount "$tmpmnt" fi +chk_ovl_opt() { + if [ -n "$2" ]; then + case ",$ovl_opts," in + *",$1=$2,"*) return 0 + esac + [ "$2" = on ] && val=Y || val=N + else + val=Y + fi + f=/sys/module/overlay/parameters/$1 + [ -e "$f" ] && [ "$(cat "$f")" = "$val" ] +} try_ovl_opt() { - case ",$extra_ovl_opts," in - *",$1[=,]"*) return + # returns 0 iff option is/gets enabled + case ",$ovl_opts," in + *",$1=off,"*) return 1;; + *",$1[=,]"*) return 0 esac - logv 'checking if %s is supported' "$1${2+=$2}" - ovl_opts="$test_ovl_opts,$1${2+=$2}$extra_ovl_opts" - mount -n -t overlay -o "$ovl_opts" "overlay" "$tmpmnt" 2>/dev/null || return + if chk_ovl_opt "$1"; then + logv 'skipping %s' + return + fi + logv 'trying %s' "$1${2+=$2}" + new_ovl_opts="$ovl_opts,$1${2+=$2}" + mount -n -t overlay -o "$new_ovl_opts" "overlay" "$tmpmnt" 2>/dev/null || return umount "$tmpmnt" || die + # clear out workdir/work/incompat/volatile and upperdir index rm -r "$workdir" "$upperdir" || die mkdir "$upperdir" "$workdir" || die - our_ovl_opts="$our_ovl_opts,$1${2+=$2}" + ovl_opts="$new_ovl_opts" } -case $lowerdir in - *:*) ;; - *) try_ovl_opt redirect_dir on - try_ovl_opt metacopy on -esac try_ovl_opt index on +# redirect_dir/metacopy are unsafe with untrusted non-bottom layers +[ "${lowerdir#*:}" = "$lowerdir" ] && \ + ! chk_ovl_opt userxattr on && \ + try_ovl_opt redirect_dir on && \ + { chk_ovl_opt nfs_export on || try_ovl_opt metacopy on; } try_ovl_opt volatile # try to match perms/attrs. this is not race-free but it's impossible without @@ -188,18 +215,18 @@ try_ovl_opt volatile lastlowerdir=${lowerdir##*:} logv 'copying lowerdir owner to upperdir' owner=$(stat -c %u:%g "$lastlowerdir") || die -chown $owner "$upperdir" || die +chown "$owner" "$upperdir" || die logv 'copying lowerdir perms to upperdir' mode=$(stat -c %a "$lastlowerdir") || die -chmod $mode "$upperdir" || die +chmod "$mode" "$upperdir" || die # -m - covers ACLs (system.posix_acl_access) and file caps # (security.capability). theoretically someone might have get/setcap and/or # get/setfacl but not get/setxattr, but this is unlikely since libcap/acl # require attr. -logv 'copying root attrs' -if attr=$(cd "$lastlowerdir" && getfattr -d -m - . 2>/dev/null); then - if [ -n "$attr" ]; then - printf '%s\n' "$attr" | (cd "$upperdir"; setfattr --restore=-) || die +logv 'copying root xattrs' +if attrs=$(cd "$lastlowerdir" && getfattr -d -m - . 2>/dev/null); then + if [ -n "$attrs" ]; then + printf '%s\n' "$attrs" | (cd "$upperdir"; setfattr --restore=-) || die fi else log 'getfattr not found or failed, skipping xattrs' @@ -207,11 +234,11 @@ fi logv 'mounting overlay' mount_opts="$no_canon $no_mtab $verbose" -ovl_opts="lowerdir=$lowerdir,upperdir=$upperdir,workdir=$workdir$our_ovl_opts$extra_ovl_opts" -mount $mount_opts -t overlay -o "$ovl_opts" "${mount_name-overlay}" "$dest" || die +# shellcheck disable=SC2086 +cmdv mount $mount_opts -t overlay -o "$ovl_opts" "${mount_name-overlay}" "$dest" || die logv 'cleaning up' umount "$tmpdir" || exit rmdir "$tmpdir" || exit -logv 'done, exiting' +logv 'done' |