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

[Paul Moore <paul@paul-moore.com>]

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>

-- 
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