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authorAlexei Starovoitov <ast@kernel.org>2018-06-07 10:23:10 -0700
committerDavid S. Miller <davem@davemloft.net>2018-06-07 16:56:28 -0400
commitbf956be520fb534510e31564231163aa05f7f091 (patch)
tree5b699323e6cb5564a0f784d981cb9f2372c8b266 /kernel/umh.c
parent2ac0e1524d9585f5261cebecca262da6cedc1d85 (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.c3
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;
}
}
}

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