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bpf: Fix umd memory leak in copy_process()

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The syzbot reported a memleak as follows:

BUG: memory leak
unreferenced object 0xffff888101b41d00 (size 120):
  comm "kworker/u4:0", pid 8, jiffies 4294944270 (age 12.780s)
  backtrace:
    [<ffffffff8125dc56>] alloc_pid+0x66/0x560
    [<ffffffff81226405>] copy_process+0x1465/0x25e0
    [<ffffffff81227943>] kernel_clone+0xf3/0x670
    [<ffffffff812281a1>] kernel_thread+0x61/0x80
    [<ffffffff81253464>] call_usermodehelper_exec_work
    [<ffffffff81253464>] call_usermodehelper_exec_work+0xc4/0x120
    [<ffffffff812591c9>] process_one_work+0x2c9/0x600
    [<ffffffff81259ab9>] worker_thread+0x59/0x5d0
    [<ffffffff812611c8>] kthread+0x178/0x1b0
    [<ffffffff8100227f>] ret_from_fork+0x1f/0x30

unreferenced object 0xffff888110ef5c00 (size 232):
  comm "kworker/u4:0", pid 8414, jiffies 4294944270 (age 12.780s)
  backtrace:
    [<ffffffff8154a0cf>] kmem_cache_zalloc
    [<ffffffff8154a0cf>] __alloc_file+0x1f/0xf0
    [<ffffffff8154a809>] alloc_empty_file+0x69/0x120
    [<ffffffff8154a8f3>] alloc_file+0x33/0x1b0
    [<ffffffff8154ab22>] alloc_file_pseudo+0xb2/0x140
    [<ffffffff81559218>] create_pipe_files+0x138/0x2e0
    [<ffffffff8126c793>] umd_setup+0x33/0x220
    [<ffffffff81253574>] call_usermodehelper_exec_async+0xb4/0x1b0
    [<ffffffff8100227f>] ret_from_fork+0x1f/0x30

After the UMD process exits, the pipe_to_umh/pipe_from_umh and
tgid need to be released.

Fixes: d71fa5c976 ("bpf: Add kernel module with user mode driver that populates bpffs.")
Reported-by: syzbot+44908bb56d2bfe56b28e@syzkaller.appspotmail.com
Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210317030915.2865-1-qiang.zhang@windriver.com
This commit is contained in:
Zqiang 2021-03-17 11:09:15 +08:00 committed by Daniel Borkmann
parent e75b513ec6
commit f60a85cad6
3 changed files with 31 additions and 10 deletions
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1
include/linux/usermode_driver.h
View File

@ -14,5 +14,6 @@ struct umd_info {
int umd_load_blob(struct umd_info *info, const void *data, size_t len);
int umd_unload_blob(struct umd_info *info);
int fork_usermode_driver(struct umd_info *info);
void umd_cleanup_helper(struct umd_info *info);
#endif /* __LINUX_USERMODE_DRIVER_H__ */

19
kernel/bpf/preload/bpf_preload_kern.c
View File

@ -60,9 +60,12 @@ static int finish(void)
&magic, sizeof(magic), &pos);
if (n != sizeof(magic))
return -EPIPE;
tgid = umd_ops.info.tgid;
wait_event(tgid->wait_pidfd, thread_group_exited(tgid));
umd_ops.info.tgid = NULL;
if (tgid) {
wait_event(tgid->wait_pidfd, thread_group_exited(tgid));
umd_cleanup_helper(&umd_ops.info);
}
return 0;
}
@ -80,10 +83,18 @@ static int __init load_umd(void)
static void __exit fini_umd(void)
{
struct pid *tgid;
bpf_preload_ops = NULL;
/* kill UMD in case it's still there due to earlier error */
kill_pid(umd_ops.info.tgid, SIGKILL, 1);
umd_ops.info.tgid = NULL;
tgid = umd_ops.info.tgid;
if (tgid) {
kill_pid(tgid, SIGKILL, 1);
wait_event(tgid->wait_pidfd, thread_group_exited(tgid));
umd_cleanup_helper(&umd_ops.info);
}
umd_unload_blob(&umd_ops.info);
}
late_initcall(load_umd);

21
kernel/usermode_driver.c
View File

@ -139,14 +139,23 @@ static void umd_cleanup(struct subprocess_info *info)
struct umd_info *umd_info = info->data;
/* cleanup if umh_setup() was successful but exec failed */
if (info->retval) {
fput(umd_info->pipe_to_umh);
fput(umd_info->pipe_from_umh);
put_pid(umd_info->tgid);
umd_info->tgid = NULL;
}
if (info->retval)
umd_cleanup_helper(umd_info);
}
/**
* umd_cleanup_helper - release the resources which were allocated in umd_setup
* @info: information about usermode driver
*/
void umd_cleanup_helper(struct umd_info *info)
{
fput(info->pipe_to_umh);
fput(info->pipe_from_umh);
put_pid(info->tgid);
info->tgid = NULL;
}
EXPORT_SYMBOL_GPL(umd_cleanup_helper);
/**
* fork_usermode_driver - fork a usermode driver
* @info: information about usermode driver (shouldn't be NULL)