diff options
| author | Alexei Starovoitov <ast@kernel.org> | 2018-06-07 10:23:10 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-06-07 16:56:28 -0400 |
| commit | bf956be520fb534510e31564231163aa05f7f091 (patch) | |
| tree | 5b699323e6cb5564a0f784d981cb9f2372c8b266 /kernel/umh.c | |
| parent | 2ac0e1524d9585f5261cebecca262da6cedc1d85 (diff) | |
umh: fix race condition
kasan reported use-after-free:
BUG: KASAN: use-after-free in call_usermodehelper_exec_work+0x2d3/0x310 kernel/umh.c:195
Write of size 4 at addr ffff8801d9202370 by task kworker/u4:2/50
Workqueue: events_unbound call_usermodehelper_exec_work
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1b9/0x294 lib/dump_stack.c:113
print_address_description+0x6c/0x20b mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
__asan_report_store4_noabort+0x17/0x20 mm/kasan/report.c:437
call_usermodehelper_exec_work+0x2d3/0x310 kernel/umh.c:195
process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
kthread+0x345/0x410 kernel/kthread.c:240
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
The reason is that 'sub_info' cannot be accessed out of parent task
context, since it will be freed by the child.
Instead remember the pid in the child task.
Fixes: 449325b52b7a ("umh: introduce fork_usermode_blob() helper")
Reported-by: syzbot+2c73319c406f1987d156@syzkaller.appspotmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/umh.c')
| -rw-r--r-- | kernel/umh.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/kernel/umh.c b/kernel/umh.c index 30db93fd7e39..c449858946af 100644 --- a/kernel/umh.c +++ b/kernel/umh.c @@ -99,6 +99,7 @@ static int call_usermodehelper_exec_async(void *data) commit_creds(new); + sub_info->pid = task_pid_nr(current); if (sub_info->file) retval = do_execve_file(sub_info->file, sub_info->argv, sub_info->envp); @@ -191,8 +192,6 @@ static void call_usermodehelper_exec_work(struct work_struct *work) if (pid < 0) { sub_info->retval = pid; umh_complete(sub_info); - } else { - sub_info->pid = pid; } } } |