base-files: fix postinstall uci-defaults removal

Commit 7f694582 introduced a bug where default_postinst() often fails to
remove a uci-defaults script after application, leaving it to run again
after a reboot.
(Note: commit 7f694582 also introduced FS#1021, now fixed by 73c745f6)

The subtle problem arises from the shell logical chain:
[ -f "$i" ] && . "$i" && rm -f "$i"

Most uci-defaults scripts contain a terminal 'exit 0' statement which,
when sourced, results in the logic chain exiting before executing 'rm -f'.
This was observed while testing upgrades of 'luci-app-sqm'.

The solution is to wrap the shell sourcing in a subshell relative to the
command 'rm -f':
( [ -f "$i" ] && . "$i" ) && rm -f "$i"

Revert to using 'grep' to prefilter the list of entries from the control
file, which yields the full path of uci-defaults scripts. This allows
keeping the existence check, directory change and script sourcing inside
the subshell, with the script removal correctly outside.

This approach avoids adding a second subshell only around the "." (source)
command. The change also preserves the fix FS#1021, since the full path is
used to source the script, which is POSIX-portable irrespective of PATH
variable or reference to the CWD.

Run Tested on: LEDE 17.01.4 running ar71xx, while tracing installation of
package luci-app-sqm with its associated /etc/uci-defaults/luci-sqm file.

Signed-off-by: Tony Ambardar <itugrok@yahoo.com>
(backported from 4097ab6a975902b170dd7f7ac6c8025e5f32ef8d)

diff --git a/package/base-files/files/lib/functions.sh b/package/base-files/files/lib/functions.sh
index 51ca8d5a0c80873b285feccc44319b5958140ba4..6858dc827a8e091825592cb7e36546f15c47f6bb 100755 (executable)
--- a/package/base-files/files/lib/functions.sh
+++ b/package/base-files/files/lib/functions.sh
@@ -243,10 +243,9 @@ default_postinst() {
        if [ -z "$root" ] && grep -q -s "^/etc/uci-defaults/" "/usr/lib/opkg/info/${pkgname}.list"; then
                . /lib/functions/system.sh
                [ -d /tmp/.uci ] || mkdir -p /tmp/.uci
-               for i in $(sed -ne 's!^/etc/uci-defaults/!!p' "/usr/lib/opkg/info/${pkgname}.list"); do (
-                       cd /etc/uci-defaults
-                       [ -f "$i" ] && . ./"$i" && rm -f "$i"
-               ) done
+               for i in $(grep -s "^/etc/uci-defaults/" "/usr/lib/opkg/info/${pkgname}.list"); do
+                       ( [ -f "$i" ] && cd "$(dirname $i)" && . "$i" ) && rm -f "$i"
+               done
                uci commit
        fi