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ctdb-common: Map ENOENT for a missing event script to ENOEXEC

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This handles the case where an event script is disabled by unlinking,
while an event is being run, after the script list has been created.
Without this change the script will fail.  With this change the script
will be marked as DISABLED.  See the comment added by this commit for
more details.

Add a testcase to simulate the race, using an event script to disable
subsequent ones.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15755
RN: Avoid event failure race when disabling an event script

Signed-off-by: Martin Schwenke <mschwenke@ddn.com>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>

Autobuild-User(master): Amitay Isaacs <amitay@samba.org>
Autobuild-Date(master): Thu Nov 21 01:42:09 UTC 2024 on atb-devel-224

(cherry picked from commit fee31b6cb2b8f7dd111bdd9d2ff5479c31cbca37)
This commit is contained in:
Martin Schwenke 2024-11-20 14:37:09 +11:00 committed by Jule Anger
parent a01a0c34da
commit 9a7047e8cc
3 changed files with 62 additions and 2 deletions
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23
ctdb/common/run_event.c
View File

@ -268,8 +268,27 @@ static int run_event_script_status(struct run_event_script *script)
if (script->result.sig > 0) {
ret = -EINTR;
} else if (script->result.err > 0) {
if (script->result.err == EACCES) {
/* Map EACCESS to ENOEXEC */
if (script->result.err == EACCES ||
script->result.err == ENOENT) {
/*
* Map EACCESS/ENOENT to ENOEXEC
*
* ENOENT: Disabling a standard event script
* by removing its symlink can result in
* ENOENT. This happens when the script list
* is built while the link exists, but the
* link is removed before the attempt to run
* it. Map it to ENOEXEC (which causes a
* script to be shown as DISABLED). This
* makes it impossible to distinguish a
* removed symlink from a dangling
* symlink... but the latter can just be
* defined as disabled. It should be rare
* because it shouldn't happen if event
* scripts are properly managed. If someone
* is doing weird things then they can easily
* debug such issues by looking at the link.
*/
ret = -ENOEXEC;
} else {
ret = -script->result.err;

4
ctdb/tests/UNIT/eventd/etc-ctdb/share/events/data/01.dummy.script
View File

@ -2,5 +2,9 @@
case "$1" in
"failure") exit 1 ;;
"disablehack")
ctdb-event script disable data 02.disabled
ctdb-event script disable data 03.notalink
;;
*) exit 0 ;;
esac

37
ctdb/tests/UNIT/eventd/eventd_009.sh
View File

@ -153,3 +153,40 @@ ok <<EOF
* 03.notalink
EOF
simple_test script list data
#
# Test disabling of scripts after the script list has been
# built. Normally this would be an admin racing with eventd instead of
# one script disabling subsequent ones.
#
# First enable all scripts - this might repeat some previous stuff
ok_null
simple_test script enable data 01.dummy
ok_null
simple_test script enable data 02.disabled
ok_null
simple_test script enable data 03.notalink
# Confirm expected state
ok <<EOF
* 01.dummy
* 02.disabled
* 03.notalink
EOF
simple_test script list data
# Now run the event that disables the subsequent scripts:
# - 02.disabled has its link removed
# - 03.notalink effectively has "chmod -x" applied
ok_null
simple_test run 10 data disablehack
# Confirm that both subsequent scripts were disabled
ok <<EOF
01.dummy OK DURATION DATETIME
02.disabled DISABLED
03.notalink DISABLED
EOF
simple_test status data disablehack