From 18414a4a2eabb0281d12d374c92874327e0e3fe3 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 30 May 2024 13:35:50 -0600 Subject: [PATCH] io_uring/net: assign kmsg inq/flags before buffer selection syzbot reports that recv is using an uninitialized value: ===================================================== BUG: KMSAN: uninit-value in io_req_cqe_overflow io_uring/io_uring.c:810 [inline] BUG: KMSAN: uninit-value in io_req_complete_post io_uring/io_uring.c:937 [inline] BUG: KMSAN: uninit-value in io_issue_sqe+0x1f1b/0x22c0 io_uring/io_uring.c:1763 io_req_cqe_overflow io_uring/io_uring.c:810 [inline] io_req_complete_post io_uring/io_uring.c:937 [inline] io_issue_sqe+0x1f1b/0x22c0 io_uring/io_uring.c:1763 io_wq_submit_work+0xa17/0xeb0 io_uring/io_uring.c:1860 io_worker_handle_work+0xc04/0x2000 io_uring/io-wq.c:597 io_wq_worker+0x447/0x1410 io_uring/io-wq.c:651 ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 Uninit was stored to memory at: io_req_set_res io_uring/io_uring.h:215 [inline] io_recv_finish+0xf10/0x1560 io_uring/net.c:861 io_recv+0x12ec/0x1ea0 io_uring/net.c:1175 io_issue_sqe+0x429/0x22c0 io_uring/io_uring.c:1751 io_wq_submit_work+0xa17/0xeb0 io_uring/io_uring.c:1860 io_worker_handle_work+0xc04/0x2000 io_uring/io-wq.c:597 io_wq_worker+0x447/0x1410 io_uring/io-wq.c:651 ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 Uninit was created at: slab_post_alloc_hook mm/slub.c:3877 [inline] slab_alloc_node mm/slub.c:3918 [inline] __do_kmalloc_node mm/slub.c:4038 [inline] __kmalloc+0x6e4/0x1060 mm/slub.c:4052 kmalloc include/linux/slab.h:632 [inline] io_alloc_async_data+0xc0/0x220 io_uring/io_uring.c:1662 io_msg_alloc_async io_uring/net.c:166 [inline] io_recvmsg_prep_setup io_uring/net.c:725 [inline] io_recvmsg_prep+0xbe8/0x1a20 io_uring/net.c:806 io_init_req io_uring/io_uring.c:2135 [inline] io_submit_sqe io_uring/io_uring.c:2182 [inline] io_submit_sqes+0x1135/0x2f10 io_uring/io_uring.c:2335 __do_sys_io_uring_enter io_uring/io_uring.c:3246 [inline] __se_sys_io_uring_enter+0x40f/0x3c80 io_uring/io_uring.c:3183 __x64_sys_io_uring_enter+0x11f/0x1a0 io_uring/io_uring.c:3183 x64_sys_call+0x2c0/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:427 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f which appears to be io_recv_finish() reading kmsg->msg.msg_inq to decide if it needs to set IORING_CQE_F_SOCK_NONEMPTY or not. If the recv is entered with buffer selection, but no buffer is available, then we jump error path which calls io_recv_finish() without having assigned kmsg->msg_inq. This might cause an errant setting of the NONEMPTY flag for a request get gets errored with -ENOBUFS. Reported-by: syzbot+b1647099e82b3b349fbf@syzkaller.appspotmail.com Fixes: 4a3223f7bfda ("io_uring/net: switch io_recv() to using io_async_msghdr") Signed-off-by: Jens Axboe --- io_uring/net.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/io_uring/net.c b/io_uring/net.c index 0a48596429d9..7c98c4d50946 100644 --- a/io_uring/net.c +++ b/io_uring/net.c @@ -1127,6 +1127,9 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags) flags |= MSG_DONTWAIT; retry_multishot: + kmsg->msg.msg_inq = -1; + kmsg->msg.msg_flags = 0; + if (io_do_buffer_select(req)) { ret = io_recv_buf_select(req, kmsg, &len, issue_flags); if (unlikely(ret)) @@ -1134,9 +1137,6 @@ retry_multishot: sr->buf = NULL; } - kmsg->msg.msg_inq = -1; - kmsg->msg.msg_flags = 0; - if (flags & MSG_WAITALL) min_ret = iov_iter_count(&kmsg->msg.msg_iter); -- 2.25.1