[PATCH v2] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()
From: Peilin Ye
Date: Wed Aug 03 2022 - 18:24:17 EST
From: Peilin Ye <peilin.ye@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Peilin Ye <peilin.ye@xxxxxxxxxxxxx>
---
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(-)
diff --git a/fs/io-wq.c b/fs/io-wq.c
index 824623bcf1a5..4d8a77a2a150 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -634,8 +634,6 @@ 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;
@@ -670,7 +668,6 @@ 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;
}
diff --git a/fs/io_uring.c b/fs/io_uring.c
index e8e769be9ed0..e0da0d2f71f2 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9208,8 +9208,6 @@ 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;
@@ -9283,8 +9281,6 @@ static int io_sq_thread(void *data)
io_run_task_work();
mutex_unlock(&sqd->lock);
- audit_free(current);
-
complete(&sqd->exited);
do_exit(0);
}
diff --git a/include/linux/audit.h b/include/linux/audit.h
index cece70231138..c313df466e6e 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -287,7 +287,6 @@ 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);
@@ -580,10 +579,6 @@ 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)
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 3a8c9d744800..dd8d9ab747c3 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -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 */
--
2.20.1