Messages in this thread Patch in this message | | | Subject | Re: KASAN: null-ptr-deref Read in rds_ib_get_mr | From | Yanjun Zhu <> | Date | Fri, 11 May 2018 15:48:50 +0800 |
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On 2018/5/11 13:20, DaeRyong Jeong wrote: > We report the crash: KASAN: null-ptr-deref Read in rds_ib_get_mr > > Note that this bug is previously reported by syzkaller. > https://syzkaller.appspot.com/bug?id=0bb56a5a48b000b52aa2b0d8dd20b1f545214d91 > Nonetheless, this bug has not fixed yet, and we hope that this report and our > analysis, which gets help by the RaceFuzzer's feature, will helpful to fix the > crash. > > This crash has been found in v4.17-rc1 using RaceFuzzer (a modified > version of Syzkaller), which we describe more at the end of this > report. Our analysis shows that the race occurs when invoking two > syscalls concurrently, bind$rds and setsockopt$RDS_GET_MR. > > > Analysis: > We think the concurrent execution of __rds_rdma_map() and rds_bind() > causes the problem. __rds_rdma_map() checks whether rs->rs_bound_addr is 0 > or not. But the concurrent execution with rds_bind() can by-pass this > check. Therefore, __rds_rdmap_map() calls rs->rs_transport->get_mr() and > rds_ib_get_mr() causes the null deref at ib_rdma.c:544 in v4.17-rc1, when > dereferencing rs_conn. > > > Thread interleaving: > CPU0 (__rds_rdma_map) CPU1 (rds_bind) > // rds_add_bound() sets rs->bound_addr as none 0 > ret = rds_add_bound(rs, sin->sin_addr.s_addr, &sin->sin_port); > if (rs->rs_bound_addr == 0 || !rs->rs_transport) { > ret = -ENOTCONN; /* XXX not a great errno */ > goto out; > } > if (rs->rs_transport) { /* previously bound */ > trans = rs->rs_transport; > if (trans->laddr_check(sock_net(sock->sk), > sin->sin_addr.s_addr) != 0) { > ret = -ENOPROTOOPT; > // rds_remove_bound() sets rs->bound_addr as 0 > rds_remove_bound(rs); > ... > trans_private = rs->rs_transport->get_mr(sg, nents, rs, > &mr->r_key); > (in rds_ib_get_mr()) > struct rds_ib_connection *ic = rs->rs_conn->c_transport_data; > > > Call sequence (v4.17-rc1): > CPU0 > rds_setsockopt > rds_get_mr > __rds_rdma_map > rds_ib_get_mr > > > CPU1 > rds_bind > rds_add_bound > ... > rds_remove_bound > > > Crash log: > ================================================================== > BUG: KASAN: null-ptr-deref in rds_ib_get_mr+0x3a/0x150 net/rds/ib_rdma.c:544 > Read of size 8 at addr 0000000000000068 by task syz-executor0/32067 > > CPU: 0 PID: 32067 Comm: syz-executor0 Not tainted 4.17.0-rc1 #1 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.2-0-g33fbe13 by qemu-project.org 04/01/2014 > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0x166/0x21c lib/dump_stack.c:113 > kasan_report_error mm/kasan/report.c:352 [inline] > kasan_report+0x140/0x360 mm/kasan/report.c:412 > check_memory_region_inline mm/kasan/kasan.c:260 [inline] > __asan_load8+0x54/0x90 mm/kasan/kasan.c:699 > rds_ib_get_mr+0x3a/0x150 net/rds/ib_rdma.c:544 > __rds_rdma_map+0x521/0x9d0 net/rds/rdma.c:271 > rds_get_mr+0xad/0xf0 net/rds/rdma.c:333 > rds_setsockopt+0x57f/0x720 net/rds/af_rds.c:347 > __sys_setsockopt+0x147/0x230 net/socket.c:1903 > __do_sys_setsockopt net/socket.c:1914 [inline] > __se_sys_setsockopt net/socket.c:1911 [inline] > __x64_sys_setsockopt+0x67/0x80 net/socket.c:1911 > do_syscall_64+0x15f/0x4a0 arch/x86/entry/common.c:287 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x4563f9 > RSP: 002b:00007f6a2b3c2b28 EFLAGS: 00000246 ORIG_RAX: 0000000000000036 > RAX: ffffffffffffffda RBX: 000000000072bee0 RCX: 00000000004563f9 > RDX: 0000000000000002 RSI: 0000000000000114 RDI: 0000000000000015 > RBP: 0000000000000575 R08: 0000000000000020 R09: 0000000000000000 > R10: 0000000020000140 R11: 0000000000000246 R12: 00007f6a2b3c36d4 > R13: 00000000ffffffff R14: 00000000006fd398 R15: 0000000000000000 > ================================================================== diff --git a/net/rds/ib_rdma.c b/net/rds/ib_rdma.c index e678699..2228b50 100644 --- a/net/rds/ib_rdma.c +++ b/net/rds/ib_rdma.c @@ -539,11 +539,17 @@ void rds_ib_flush_mrs(void) void *rds_ib_get_mr(struct scatterlist *sg, unsigned long nents, struct rds_sock *rs, u32 *key_ret) { - struct rds_ib_device *rds_ibdev; + struct rds_ib_device *rds_ibdev = NULL; struct rds_ib_mr *ibmr = NULL; - struct rds_ib_connection *ic = rs->rs_conn->c_transport_data; + struct rds_ib_connection *ic = NULL; int ret;
+ if (rs->rs_bound_addr == 0) { + ret = -EPERM; + goto out; + } + + ic = rs->rs_conn->c_transport_data; rds_ibdev = rds_ib_get_device(rs->rs_bound_addr); if (!rds_ibdev) { ret = -ENODEV;
I made this raw patch. If you can reproduce this bug, please make tests with it.
Thanks a lot. > > = About RaceFuzzer > > RaceFuzzer is a customized version of Syzkaller, specifically tailored > to find race condition bugs in the Linux kernel. While we leverage > many different technique, the notable feature of RaceFuzzer is in > leveraging a custom hypervisor (QEMU/KVM) to interleave the > scheduling. In particular, we modified the hypervisor to intentionally > stall a per-core execution, which is similar to supporting per-core > breakpoint functionality. This allows RaceFuzzer to force the kernel > to deterministically trigger racy condition (which may rarely happen > in practice due to randomness in scheduling). > > RaceFuzzer's C repro always pinpoints two racy syscalls. Since C > repro's scheduling synchronization should be performed at the user > space, its reproducibility is limited (reproduction may take from 1 > second to 10 minutes (or even more), depending on a bug). This is > because, while RaceFuzzer precisely interleaves the scheduling at the > kernel's instruction level when finding this bug, C repro cannot fully > utilize such a feature. Please disregard all code related to > "should_hypercall" in the C repro, as this is only for our debugging > purposes using our own hypervisor. >
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