Re: [PATCH v2] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

[Jens Axboe <axboe@kernel.dk>]

On 8/4/22 7:51 AM, Paul Moore wrote:
> On Wed, Aug 3, 2022 at 6:24 PM Peilin Ye <yepeilin.cs@gmail.com> wrote:
>>
>> From: Peilin Ye <peilin.ye@bytedance.com>
>>
>> Currently @audit_context is allocated twice for io_uring workers:
>>
>>   1. copy_process() calls audit_alloc();
>>   2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
>>      is effectively audit_alloc()) and overwrites @audit_context,
>>      causing:
>>
>>   BUG: memory leak
>>   unreferenced object 0xffff888144547400 (size 1024):
>> <...>
>>     hex dump (first 32 bytes):
>>       00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00  ................
>>       00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>     backtrace:
>>       [<ffffffff8135cfc3>] audit_alloc+0x133/0x210
>>       [<ffffffff81239e63>] copy_process+0xcd3/0x2340
>>       [<ffffffff8123b5f3>] create_io_thread+0x63/0x90
>>       [<ffffffff81686604>] create_io_worker+0xb4/0x230
>>       [<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
>>       [<ffffffff8167663a>] io_queue_iowq+0xba/0x200
>>       [<ffffffff816768b3>] io_queue_async+0x113/0x180
>>       [<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
>>       [<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
>>       [<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
>>       [<ffffffff81272c4e>] task_work_run+0x7e/0xc0
>>       [<ffffffff8125a688>] get_signal+0xc18/0xf10
>>       [<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
>>       [<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
>>       [<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
>>       [<ffffffff844a7e80>] do_syscall_64+0x40/0x80
>>
>> Then,
>>
>>   3. io_sq_thread() or io_wqe_worker() frees @audit_context using
>>      audit_free();
>>   4. do_exit() eventually calls audit_free() again, which is okay
>>      because audit_free() does a NULL check.
>>
>> As suggested by Paul Moore, fix it by deleting audit_alloc_kernel() and
>> redundant audit_free() calls.
>>
>> Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
>> Suggested-by: Paul Moore <paul@paul-moore.com>
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
>> ---
>> Change since v1:
>>   - Delete audit_alloc_kernel() (Paul Moore)
>>
>>  fs/io-wq.c            |  3 ---
>>  fs/io_uring.c         |  4 ----
>>  include/linux/audit.h |  5 -----
>>  kernel/auditsc.c      | 25 -------------------------
>>  4 files changed, 37 deletions(-)
> 
> This looks good to me, thanks!  Although it looks like the io_uring
> related changes will need to be applied by hand as they are pointing
> to the old layout under fs/ as opposed to the newer layout in
> io_uring/ introduced during this merge window.
> 
> Jens, did you want to take this via the io_uring tree or should I take
> it via the audit tree?  If the latter, an ACK would be appreciated, if
> the former my ACK is below.
> 
> Acked-by: Paul Moore <paul@paul-moore.com>

Probably better if I take it, since I need to massage it into the
current tree anyway. We can then use this one as the base for the stable
backports that are going to be required.

-- 
Jens Axboe