[PATCH] io_uring: fix uninit-value in io_sendrecv_fail

[Edward Adam Davis <eadavis@qq.com>]

[Syzbot reported]
BUG: KMSAN: uninit-value in io_sendrecv_fail+0x91/0x1e0 io_uring/net.c:1334
 io_sendrecv_fail+0x91/0x1e0 io_uring/net.c:1334
 io_req_defer_failed+0x3bd/0x610 io_uring/io_uring.c:1050
 io_queue_sqe_fallback+0x1e3/0x280 io_uring/io_uring.c:2126
 io_submit_fail_init+0x4e1/0x790 io_uring/io_uring.c:2304
 io_submit_sqes+0x19cd/0x2fb0 io_uring/io_uring.c:2480
 __do_sys_io_uring_enter io_uring/io_uring.c:3656 [inline]
 __se_sys_io_uring_enter+0x409/0x43e0 io_uring/io_uring.c:3591
 __x64_sys_io_uring_enter+0x11b/0x1a0 io_uring/io_uring.c:3591
 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+0x63/0x6b

Uninit was created at:
 __alloc_pages+0x9a6/0xe00 mm/page_alloc.c:4592
 __alloc_pages_node include/linux/gfp.h:238 [inline]
 alloc_pages_node include/linux/gfp.h:261 [inline]
 alloc_slab_page mm/slub.c:2190 [inline]
 allocate_slab mm/slub.c:2354 [inline]
 new_slab+0x2d7/0x1400 mm/slub.c:2407
 ___slab_alloc+0x16b5/0x3970 mm/slub.c:3540
 __kmem_cache_alloc_bulk mm/slub.c:4574 [inline]
 kmem_cache_alloc_bulk+0x52a/0x1440 mm/slub.c:4648
 __io_alloc_req_refill+0x248/0x780 io_uring/io_uring.c:1101
 io_alloc_req io_uring/io_uring.h:405 [inline]
 io_submit_sqes+0xaa1/0x2fb0 io_uring/io_uring.c:2469
 __do_sys_io_uring_enter io_uring/io_uring.c:3656 [inline]
 __se_sys_io_uring_enter+0x409/0x43e0 io_uring/io_uring.c:3591
 __x64_sys_io_uring_enter+0x11b/0x1a0 io_uring/io_uring.c:3591
 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+0x63/0x6b

[Fix] 
When initializing the req object, increase its member cmd initialization.

Reported-and-tested-by: syzbot+f8e9a371388aa62ecab4@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
---
 io_uring/io_uring.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index cd9a137ad6ce..3db59fd6f676 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -1066,6 +1066,7 @@ static void io_preinit_req(struct io_kiocb *req, struct io_ring_ctx *ctx)
 	/* not necessary, but safer to zero */
 	memset(&req->cqe, 0, sizeof(req->cqe));
 	memset(&req->big_cqe, 0, sizeof(req->big_cqe));
+	memset(&req->cmd, 0, sizeof(req->cmd));
 }
 
 static void io_flush_cached_locked_reqs(struct io_ring_ctx *ctx,
-- 
2.43.0