The patch below does not apply to the 5.19-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 stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From f482aa98652795846cc55da98ebe331eb74f3d0b Mon Sep 17 00:00:00 2001 From: Peilin Ye peilin.ye@bytedance.com 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 paul@paul-moore.com Cc: stable@vger.kernel.org Signed-off-by: Peilin Ye peilin.ye@bytedance.com Acked-by: Paul Moore paul@paul-moore.com Link: https://lore.kernel.org/r/20220803222343.31673-1-yepeilin.cs@gmail.com Signed-off-by: Jens Axboe axboe@kernel.dk
diff --git a/include/linux/audit.h b/include/linux/audit.h index 00f7a80f1a3e..3608992848d3 100644 --- a/include/linux/audit.h +++ b/include/linux/audit.h @@ -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) diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c index 77df5b43bf52..c6536d4b2da0 100644 --- a/io_uring/io-wq.c +++ b/io_uring/io-wq.c @@ -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; } diff --git a/io_uring/sqpoll.c b/io_uring/sqpoll.c index 76d4d70c733a..559652380672 100644 --- a/io_uring/sqpoll.c +++ b/io_uring/sqpoll.c @@ -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); } 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 */