From f482aa98652795846cc55da98ebe331eb74f3d0b Mon Sep 17 00:00:00 2001 From: Peilin Ye Date: Wed, 3 Aug 2022 15:23:43 -0700 Subject: 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: [] audit_alloc+0x133/0x210 [] copy_process+0xcd3/0x2340 [] create_io_thread+0x63/0x90 [] create_io_worker+0xb4/0x230 [] io_wqe_enqueue+0x248/0x3b0 [] io_queue_iowq+0xba/0x200 [] io_queue_async+0x113/0x180 [] io_req_task_submit+0x18f/0x1a0 [] io_apoll_task_func+0xdd/0x120 [] tctx_task_work+0x11f/0x570 [] task_work_run+0x7e/0xc0 [] get_signal+0xc18/0xf10 [] arch_do_signal_or_restart+0x2b/0x730 [] exit_to_user_mode_prepare+0x5e/0x180 [] syscall_exit_to_user_mode+0x12/0x20 [] 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 Cc: stable@vger.kernel.org Signed-off-by: Peilin Ye Acked-by: Paul Moore Link: https://lore.kernel.org/r/20220803222343.31673-1-yepeilin.cs@gmail.com Signed-off-by: Jens Axboe --- kernel/auditsc.c | 25 ------------------------- 1 file changed, 25 deletions(-) (limited to 'kernel/auditsc.c') 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 */ -- cgit v1.2.3