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[188.28.201.74]) by smtp.gmail.com with ESMTPSA id k22-20020a05600c1c9600b003b340f00f10sm2806917wms.31.2022.09.23.07.01.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Sep 2022 07:01:01 -0700 (PDT) From: Pavel Begunkov To: io-uring@vger.kernel.org Cc: Jens Axboe , asml.silence@gmail.com, Dylan Yudaken , syzbot+4c597a574a3f5a251bda@syzkaller.appspotmail.com Subject: [PATCH for-next 1/1] io_uring/net: fix UAF in io_sendrecv_fail() Date: Fri, 23 Sep 2022 14:59:47 +0100 Message-Id: <49ee34929051a668e4829b6549dcd3eba49bf95b.1663941567.git.asml.silence@gmail.com> X-Mailer: git-send-email 2.37.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org We should not assume anything about ->free_iov just from REQ_F_ASYNC_DATA but rather rely on REQ_F_NEED_CLEANUP, as we may allocate ->async_data but failed init would leave the field in not consistent state. The easiest solution is to remove removing REQ_F_NEED_CLEANUP and so ->async_data dealloc from io_sendrecv_fail() and let io_send_zc_cleanup() do the job. The catch here is that we also need to prevent double notif flushing, just test it for NULL and zero where it's needed. BUG: KASAN: use-after-free in io_sendrecv_fail+0x3b0/0x3e0 io_uring/net.c:1221 Write of size 8 at addr ffff8880771b4080 by task syz-executor.3/30199 CPU: 1 PID: 30199 Comm: syz-executor.3 Not tainted 6.0.0-rc6-next-20220923-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:284 [inline] print_report+0x15e/0x45d mm/kasan/report.c:395 kasan_report+0xbb/0x1f0 mm/kasan/report.c:495 io_sendrecv_fail+0x3b0/0x3e0 io_uring/net.c:1221 io_req_complete_failed+0x155/0x1b0 io_uring/io_uring.c:873 io_drain_req io_uring/io_uring.c:1648 [inline] io_queue_sqe_fallback.cold+0x29f/0x788 io_uring/io_uring.c:1931 io_submit_sqe io_uring/io_uring.c:2160 [inline] io_submit_sqes+0x1180/0x1df0 io_uring/io_uring.c:2276 __do_sys_io_uring_enter+0xac6/0x2410 io_uring/io_uring.c:3216 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd Fixes: c4c0009e0b56e ("io_uring/net: combine fail handlers") Reported-by: syzbot+4c597a574a3f5a251bda@syzkaller.appspotmail.com Signed-off-by: Pavel Begunkov --- io_uring/net.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/io_uring/net.c b/io_uring/net.c index 757a300578f4..e9e66bace45f 100644 --- a/io_uring/net.c +++ b/io_uring/net.c @@ -915,9 +915,11 @@ void io_send_zc_cleanup(struct io_kiocb *req) io = req->async_data; kfree(io->free_iov); } - zc->notif->flags |= REQ_F_CQE_SKIP; - io_notif_flush(zc->notif); - zc->notif = NULL; + if (zc->notif) { + zc->notif->flags |= REQ_F_CQE_SKIP; + io_notif_flush(zc->notif); + zc->notif = NULL; + } } int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) @@ -1215,12 +1217,6 @@ void io_sendrecv_fail(struct io_kiocb *req) io_notif_flush(sr->notif); sr->notif = NULL; } - if (req_has_async_data(req)) { - io = req->async_data; - kfree(io->free_iov); - io->free_iov = NULL; - } - req->flags &= ~REQ_F_NEED_CLEANUP; io_req_set_res(req, res, req->cqe.flags); }