Commit f482aa98 authored by Peilin Ye's avatar Peilin Ye Committed by Jens Axboe
Browse files

audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker() 



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: 5bd2182d ("audit,io_uring,io-wq: add some basic audit support to io_uring")
Suggested-by: default avatarPaul Moore <paul@paul-moore.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarPeilin Ye <peilin.ye@bytedance.com>
Acked-by: default avatarPaul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20220803222343.31673-1-yepeilin.cs@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent ff2557b7

include/linux/audit.h

+0 −5
Original line number Diff line number Diff line
@@ -285,7 +285,6 @@ static inline int audit_signal_info(int sig, struct task_struct *t) 
/* These are defined in auditsc.c */

				/* Public API */

extern int  audit_alloc(struct task_struct *task);

extern int  audit_alloc_kernel(struct task_struct *task);

extern void __audit_free(struct task_struct *task);

extern void __audit_uring_entry(u8 op);

extern void __audit_uring_exit(int success, long code);
@@ -578,10 +577,6 @@ static inline int audit_alloc(struct task_struct *task) 
{

	return 0;

}

static inline int audit_alloc_kernel(struct task_struct *task)

{

	return 0;

}

static inline void audit_free(struct task_struct *task)

{ }

static inline void audit_uring_entry(u8 op)

io_uring/io-wq.c

+0 −3
Original line number Diff line number Diff line
@@ -624,8 +624,6 @@ static int io_wqe_worker(void *data) 
	snprintf(buf, sizeof(buf), "iou-wrk-%d", wq->task->pid);

	set_task_comm(current, buf);



	audit_alloc_kernel(current);



	while (!test_bit(IO_WQ_BIT_EXIT, &wq->state)) {

		long ret;
@@ -660,7 +658,6 @@ static int io_wqe_worker(void *data) 
	if (test_bit(IO_WQ_BIT_EXIT, &wq->state))

		io_worker_handle_work(worker);



	audit_free(current);

	io_worker_exit(worker);

	return 0;

}

io_uring/sqpoll.c

+0 −4
Original line number Diff line number Diff line
@@ -235,8 +235,6 @@ static int io_sq_thread(void *data) 
		set_cpus_allowed_ptr(current, cpu_online_mask);

	current->flags |= PF_NO_SETAFFINITY;



	audit_alloc_kernel(current);



	mutex_lock(&sqd->lock);

	while (1) {

		bool cap_entries, sqt_spin = false;
@@ -310,8 +308,6 @@ static int io_sq_thread(void *data) 
	io_run_task_work();

	mutex_unlock(&sqd->lock);



	audit_free(current);



	complete(&sqd->exited);

	do_exit(0);

}

kernel/auditsc.c

+0 −25
Original line number Diff line number Diff line
@@ -1073,31 +1073,6 @@ int audit_alloc(struct task_struct *tsk) 
	return 0;

}



/**

 * audit_alloc_kernel - allocate an audit_context for a kernel task

 * @tsk: the kernel task

 *

 * Similar to the audit_alloc() function, but intended for kernel private

 * threads.  Returns zero on success, negative values on failure.

 */

int audit_alloc_kernel(struct task_struct *tsk)

{

	/*

	 * At the moment we are just going to call into audit_alloc() to

	 * simplify the code, but there two things to keep in mind with this

	 * approach:

	 *

	 * 1. Filtering internal kernel tasks is a bit laughable in almost all

	 * cases, but there is at least one case where there is a benefit:

	 * the '-a task,never' case allows the admin to effectively disable

	 * task auditing at runtime.

	 *

	 * 2. The {set,clear}_task_syscall_work() ops likely have zero effect

	 * on these internal kernel tasks, but they probably don't hurt either.

	 */

	return audit_alloc(tsk);

}



static inline void audit_free_context(struct audit_context *context)

{

	/* resetting is extra work, but it is likely just noise */