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libubox: runqueue: fix use-after-free bug

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Fixes a use-after-free bug in runqueue_task_kill():

 Invalid read of size 8
    at runqueue_task_kill (runqueue.c:200)
    by uloop_process_timeouts (uloop.c:505)
    by uloop_run_timeout (uloop.c:542)
    by uloop_run (uloop.h:111)
    by main (tests/test-runqueue.c:126)
  Address 0x5a4b058 is 24 bytes inside a block of size 208 free'd
    at free
    by runqueue_task_complete (runqueue.c:234)
    by runqueue_task_kill (runqueue.c:199)
    by uloop_process_timeouts (uloop.c:505)
    by uloop_run_timeout (uloop.c:542)
    by uloop_run (uloop.h:111)
    by main (tests/test-runqueue.c:126)
  Block was alloc'd at
    at calloc
    by add_sleeper (tests/test-runqueue.c:101)
    by main (tests/test-runqueue.c:123)

Since commit 11e8afea (runqueue should call the complete handler from
more places) the call to the complete() callback has been moved to
runqueue_task_complete().  However in runqueue_task_kill()
runqueue_task_complete() is called before the kill() callback.  This
will result in a use after free if the complete() callback frees the
task struct.

Furthermore runqueue_start_next() is already called at the end of
runqueue_task_complete(), so there is no need to call it again in
runqueue_task_kill().

The issue was that the _complete() callback frees the memory used by the
task struct, which is then read after the _complete() callback returns.

Ref: FS#3016
Signed-off-by: Alban Bedel <albeu@free.fr>
[initial test case, kill cb comment fix]
Signed-off-by: Chris Nisbet <nischris@gmail.com>
[testcase improvements and commit subject/description tweaks]
Signed-off-by: Petr Štetiar <ynezz@true.cz>
This commit is contained in:
Alban Bedel 2020-04-23 15:35:23 +12:00 committed by Petr Štetiar
parent 1db3e7df31
commit 89fb6136ad
4 changed files with 87 additions and 31 deletions
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3
runqueue.c
View file

@ -196,11 +196,10 @@ void runqueue_task_kill(struct runqueue_task *t)
if (!t->queued)
return;
runqueue_task_complete(t);
if (running && t->type->kill)
t->type->kill(q, t);
runqueue_start_next(q);
runqueue_task_complete(t);
}
void runqueue_stop(struct runqueue *q)

2
runqueue.h
View file

@ -63,7 +63,7 @@ struct runqueue_task_type {
/*
* called to kill a task. must not make any calls to runqueue_task_complete,
* it has already been removed from the list.
* which will be called after this returns.
*/
void (*kill)(struct runqueue *q, struct runqueue_task *t);
};

46
tests/cram/test_runqueue.t
View file

@ -2,25 +2,35 @@ check that runqueue is producing expected results:
$ [ -n "$TEST_BIN_DIR" ] && export PATH="$TEST_BIN_DIR:$PATH"
$ valgrind --quiet --leak-check=full test-runqueue
[1/1] start 'sleep 1'
[1/1] cancel 'sleep 1'
[0/1] finish 'sleep 1'
[1/1] start 'sleep 1'
[1/1] cancel 'sleep 1'
[0/1] finish 'sleep 1'
[1/1] start 'sleep 1'
[1/1] cancel 'sleep 1'
[0/1] finish 'sleep 1'
[1/1] start 'sleep 1' (killer)
[1/1] killing process (killer)
[0/1] finish 'sleep 1' (killer)
[0/1] finish 'sleep 1' (killer)
[0/1] finish 'sleep 1' (killer)
[1/1] start 'sleep 1' (sleeper)
[1/1] cancel 'sleep 1' (sleeper)
[0/1] finish 'sleep 1' (sleeper)
[1/1] start 'sleep 1' (sleeper)
[1/1] cancel 'sleep 1' (sleeper)
[0/1] finish 'sleep 1' (sleeper)
[1/1] start 'sleep 1' (sleeper)
[1/1] cancel 'sleep 1' (sleeper)
[0/1] finish 'sleep 1' (sleeper)
All done!
$ test-runqueue-san
[1/1] start 'sleep 1'
[1/1] cancel 'sleep 1'
[0/1] finish 'sleep 1'
[1/1] start 'sleep 1'
[1/1] cancel 'sleep 1'
[0/1] finish 'sleep 1'
[1/1] start 'sleep 1'
[1/1] cancel 'sleep 1'
[0/1] finish 'sleep 1'
[1/1] start 'sleep 1' (killer)
[1/1] killing process (killer)
[0/1] finish 'sleep 1' (killer)
[0/1] finish 'sleep 1' (killer)
[0/1] finish 'sleep 1' (killer)
[1/1] start 'sleep 1' (sleeper)
[1/1] cancel 'sleep 1' (sleeper)
[0/1] finish 'sleep 1' (sleeper)
[1/1] start 'sleep 1' (sleeper)
[1/1] cancel 'sleep 1' (sleeper)
[0/1] finish 'sleep 1' (sleeper)
[1/1] start 'sleep 1' (sleeper)
[1/1] cancel 'sleep 1' (sleeper)
[0/1] finish 'sleep 1' (sleeper)
All done!

67
tests/test-runqueue.c
View file

@ -16,6 +16,7 @@
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
@ -26,8 +27,10 @@
static struct runqueue q;
struct sleeper {
struct runqueue_process proc;
int val;
bool kill;
struct uloop_timeout t;
struct runqueue_process proc;
};
static void q_empty(struct runqueue *q)
@ -36,13 +39,19 @@ static void q_empty(struct runqueue *q)
uloop_end();
}
static const char* sleeper_type(struct sleeper *s)
{
return s->kill ? "killer" : "sleeper";
}
static void q_sleep_run(struct runqueue *q, struct runqueue_task *t)
{
struct sleeper *s = container_of(t, struct sleeper, proc.task);
char str[32];
pid_t pid;
fprintf(stderr, "[%d/%d] start 'sleep %d'\n", q->running_tasks, q->max_running_tasks, s->val);
fprintf(stderr, "[%d/%d] start 'sleep %d' (%s)\n", q->running_tasks,
q->max_running_tasks, s->val, sleeper_type(s));
pid = fork();
if (pid < 0)
@ -62,7 +71,8 @@ static void q_sleep_cancel(struct runqueue *q, struct runqueue_task *t, int type
{
struct sleeper *s = container_of(t, struct sleeper, proc.task);
fprintf(stderr, "[%d/%d] cancel 'sleep %d'\n", q->running_tasks, q->max_running_tasks, s->val);
fprintf(stderr, "[%d/%d] cancel 'sleep %d' (%s)\n", q->running_tasks,
q->max_running_tasks, s->val, sleeper_type(s));
runqueue_process_cancel_cb(q, t, type);
}
@ -70,10 +80,40 @@ static void q_sleep_complete(struct runqueue *q, struct runqueue_task *p)
{
struct sleeper *s = container_of(p, struct sleeper, proc.task);
fprintf(stderr, "[%d/%d] finish 'sleep %d'\n", q->running_tasks, q->max_running_tasks, s->val);
fprintf(stderr, "[%d/%d] finish 'sleep %d' (%s) \n", q->running_tasks,
q->max_running_tasks, s->val, sleeper_type(s));
free(s);
}
static void my_runqueue_process_kill_cb(struct runqueue *q, struct runqueue_task *p)
{
struct sleeper *s = container_of(p, struct sleeper, proc.task);
fprintf(stderr, "[%d/%d] killing process (%s)\n", q->running_tasks,
q->max_running_tasks, sleeper_type(s));
runqueue_process_kill_cb(q, p);
}
static void timer_cb(struct uloop_timeout *t)
{
struct sleeper *s = container_of(t, struct sleeper, t);
if (s->kill)
runqueue_task_kill(&s->proc.task);
}
static struct sleeper* create_sleeper(int val, const struct runqueue_task_type *type, bool kill)
{
struct sleeper *s = calloc(1, sizeof(*s));
s->kill = kill;
s->t.cb = timer_cb;
s->proc.task.type = type;
s->proc.task.run_timeout = 500;
s->proc.task.complete = q_sleep_complete;
s->val = val;
return s;
}
static void add_sleeper(int val)
{
static const struct runqueue_task_type sleeper_type = {
@ -81,13 +121,19 @@ static void add_sleeper(int val)
.cancel = q_sleep_cancel,
.kill = runqueue_process_kill_cb,
};
struct sleeper *s;
s = calloc(1, sizeof(*s));
s->proc.task.type = &sleeper_type;
s->proc.task.run_timeout = 500;
s->proc.task.complete = q_sleep_complete;
s->val = val;
static const struct runqueue_task_type killer_type = {
.run = q_sleep_run,
.cancel = q_sleep_cancel,
.kill = my_runqueue_process_kill_cb,
};
struct sleeper *k = create_sleeper(val, &killer_type, true);
uloop_timeout_set(&k->t, 100);
uloop_timeout_add(&k->t);
runqueue_task_add(&q, &k->proc.task, false);
struct sleeper *s = create_sleeper(val, &sleeper_type, false);
runqueue_task_add(&q, &s->proc.task, false);
}
@ -105,6 +151,7 @@ int main(int argc, char **argv)
add_sleeper(1);
add_sleeper(1);
add_sleeper(1);
uloop_run();
uloop_done();