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libct/nsenter: sprinkle missing sane_kill

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Add a few missing sane_kill calls where they make sense.

Remove one useless sane_kill of stage2_pid, as during SYNC_USERMAP stage2
is not yet started. It is harmless yet it makes the code slightly harder
to read.

Set the child pid to -1 upon receiving SYNC_CHILD_FINISH
to minimize the chances of killing an unrelated process.
When a child sends SYNC_CHILD_FINISH it is about to exit
(although theoretically it could be stuck during debug logging).

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
This commit is contained in:
Kir Kolyshkin
2025-10-26 15:58:44 -07:00
parent 067b8335e7
commit aea52d0ab0
1 changed files with 18 additions and 5 deletions
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23
libcontainer/nsenter/nsexec.c
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@@ -848,8 +848,10 @@ void nsexec(void)
bail("unable to spawn stage-1");
syncfd = sync_child_pipe[1];
if (close(sync_child_pipe[0]) < 0)
if (close(sync_child_pipe[0]) < 0) {
sane_kill(stage1_pid, SIGKILL);
bail("failed to close sync_child_pipe[0] fd");
}
/*
* State machine for synchronisation with the children. We only
@@ -860,8 +862,11 @@ void nsexec(void)
while (!stage1_complete) {
enum sync_t s;
if (read(syncfd, &s, sizeof(s)) != sizeof(s))
if (read(syncfd, &s, sizeof(s)) != sizeof(s)) {
sane_kill(stage1_pid, SIGKILL);
sane_kill(stage2_pid, SIGKILL);
bail("failed to sync with stage-1: next state");
}
switch (s) {
case SYNC_USERMAP_PLS:
@@ -887,7 +892,6 @@ void nsexec(void)
s = SYNC_USERMAP_ACK;
if (write(syncfd, &s, sizeof(s)) != sizeof(s)) {
sane_kill(stage1_pid, SIGKILL);
sane_kill(stage2_pid, SIGKILL);
bail("failed to sync with stage-1: write(SYNC_USERMAP_ACK)");
}
break;
@@ -938,8 +942,11 @@ void nsexec(void)
case SYNC_CHILD_FINISH:
write_log(DEBUG, "stage-1 complete");
stage1_complete = true;
stage1_pid = -1;
break;
default:
sane_kill(stage1_pid, SIGKILL);
sane_kill(stage2_pid, SIGKILL);
bailx("unexpected sync value: %u", s);
}
}
@@ -947,8 +954,10 @@ void nsexec(void)
/* Now sync with grandchild. */
syncfd = sync_grandchild_pipe[1];
if (close(sync_grandchild_pipe[0]) < 0)
if (close(sync_grandchild_pipe[0]) < 0) {
sane_kill(stage2_pid, SIGKILL);
bail("failed to close sync_grandchild_pipe[0] fd");
}
write_log(DEBUG, "-> stage-2 synchronisation loop");
stage2_complete = false;
@@ -962,15 +971,19 @@ void nsexec(void)
bail("failed to sync with child: write(SYNC_GRANDCHILD)");
}
if (read(syncfd, &s, sizeof(s)) != sizeof(s))
if (read(syncfd, &s, sizeof(s)) != sizeof(s)) {
sane_kill(stage2_pid, SIGKILL);
bail("failed to sync with child: next state");
}
switch (s) {
case SYNC_CHILD_FINISH:
write_log(DEBUG, "stage-2 complete");
stage2_complete = true;
stage2_pid = -1;
break;
default:
sane_kill(stage2_pid, SIGKILL);
bailx("unexpected sync value: %u", s);
}
}