[pacman-dev] [PATCH 1/3] repo-add: Avoid race condition in signal handlers

There is a small chance that a user sends SIGINT (or any other signal that is trapped) when we're already in clean_up() which used to lead to trap_exit() being executed and the remaining code in clean_up() being skipped due to the bash signal/trap handler blocking EXIT (since its handler is already being executed, even if it's interrupted). In practice, this behaviour caused unexpected results (primarily because pressing ^C at the wrong time left a lock file behind): $ ./repo-add extra.db.tar.gz foobar ==> Extracting database to a temporary location... ^C ==> ERROR: Aborted by user! Exiting... $ ./repo-add extra.db.tar.gz foobar ==> Extracting database to a temporary location... ==> ERROR: File 'foobar' not found. ==> No packages modified, nothing to do. ^C ==> ERROR: Aborted by user! Exiting... $ ./repo-add extra.db.tar.gz foobar ==> ERROR: Failed to acquire lockfile: extra.db.tar.gz.lck. ==> ERROR: Held by process 18522 Fix this and reduce the chance of race conditions in signal handlers by: * Unhooking all traps in both clean_up() and trap_exit(). * Call clean_up() explicitly in trap_exit() to make sure we remove the lock file and the temporary directory even if we send SIGINT when clean_up() is already being executed but didn't reach the unhook code yet. Also, add an optional parameter to clean_up() to allow for setting an explicit exit code when we call clean_up() from trap_exit(). Signed-off-by: Lukas Fleischer --- scripts/repo-add.sh.in | 10 ++++++++-- 1 files changed, 8 insertions(+), 2 deletions(-) diff --git a/scripts/repo-add.sh.in b/scripts/repo-add.sh.in index 29b150c..d147b87 100644 --- a/scripts/repo-add.sh.in +++ b/scripts/repo-add.sh.in @@ -520,13 +520,19 @@ remove() { } trap_exit() { + # unhook all traps to avoid race conditions + trap '' EXIT TERM HUP QUIT INT ERR + echo error "$@" - exit 1 + clean_up 1 } clean_up() { - local exit_code=$? + local exit_code=${1:-$?} + + # unhook all traps to avoid race conditions + trap '' EXIT TERM HUP QUIT INT ERR [[ -d $tmpdir ]] && rm -rf "$tmpdir" (( CLEAN_LOCK )) && [[ -f $LOCKFILE ]] && rm -f "$LOCKFILE" -- 1.7.7