Skip to contentSkip to conversation

FAILED: patch "[PATCH] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and" failed to apply to 5.18-stable tree

PATCH [email protected] 1 participant 1 message Aug 14, 2022

Subsystems (3)
Stable branch io_uring Audit
lore
Share & tools
lore

[email protected]

author maintainer
#0 lore raw

The patch below does not apply to the 5.18-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f482aa98652795846cc55da98ebe331eb74f3d0b Mon Sep 17 00:00:00 2001
From: Peilin Ye <[email protected]>
Date: Wed, 3 Aug 2022 15:23:43 -0700
Subject: [PATCH] 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 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
Suggested-by Paul Moore <[email protected]>
Cc [email protected]
Signed-off-by Peilin Ye <[email protected]>
Acked-by Paul Moore <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
Signed-off-by Jens Axboe <[email protected]>
include/linux/audit.h +0 -5
index 00f7a80f1a3e..3608992848d3 100644
@@ -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
index 77df5b43bf52..c6536d4b2da0 100644
@@ -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
index 76d4d70c733a..559652380672 100644
@@ -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
index 3a8c9d744800..dd8d9ab747c3 100644
@@ -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 */