On Thu, Oct 25, 2018 at 12:35 PM Kyungtae Kim <kt0...@gmail.com> wrote: > > We report two crashes related (in v4.19-rc8) : > "BUG: KMSAN: uninit-value in selinux_socket_bind" > "BUG: KMSAN: uninit-value in selinux_socket_connect_helper” > > kernel config: https://kt0755.github.io/etc/config-4.19-rc2.kmsan > repro: https://kt0755.github.io/etc/repro.b0e55.c > > Since both crashes share the same issue, we just explain one of the two. > When the third argument of bind() (i.e., addrlen) is zero, in __sys_bind(), > data copy from user sockaddr to kernel sockaddr does not occur > (net/socket.c:186). > However, a subsequent function selinux_socket_bind() tries to read > the kernel sockaddr (address->sa_family) that was not initialized at all. > > Crash log1 > ================================================================== > BUG: KMSAN: uninit-value in selinux_socket_bind+0x61b/0x1040 > security/selinux/hooks.c:4643 > CPU: 0 PID: 19070 Comm: syz-executor6 Not tainted 4.19.0-rc8+ #18 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0x305/0x460 lib/dump_stack.c:113 > kmsan_report+0x1a2/0x2e0 mm/kmsan/kmsan.c:917 > __msan_warning+0x7d/0xe0 mm/kmsan/kmsan_instr.c:500 > selinux_socket_bind+0x61b/0x1040 security/selinux/hooks.c:4643 > security_socket_bind+0x127/0x200 security/security.c:1390 > __sys_bind+0x577/0x7e0 net/socket.c:1479 > __do_sys_bind net/socket.c:1494 [inline] > __se_sys_bind+0x8d/0xb0 net/socket.c:1492 > __x64_sys_bind+0x4a/0x70 net/socket.c:1492 > do_syscall_64+0xb8/0x100 arch/x86/entry/common.c:291 > entry_SYSCALL_64_after_hwframe+0x63/0xe7 > RIP: 0033:0x4497b9 > Code: e8 8c 9f 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 > 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d > 01 f0 ff ff 0f 83 9b 6b fc ff c3 66 2e 0f 1f 84 00 00 00 00 > RSP: 002b:00007fdddf1e9c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000031 > RAX: ffffffffffffffda RBX: 00007fdddf1ea6cc RCX: 00000000004497b9 > RDX: 0000000000000000 RSI: 0000000020000040 RDI: 0000000000000013 > RBP: 000000000071bea0 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff > R13: 00000000000004c8 R14: 00000000006e8568 R15: 00007fdddf1ea700 > > Local variable description: ----address@__sys_bind > Variable was created at: > __sys_bind+0x89/0x7e0 net/socket.c:1470 > __do_sys_bind net/socket.c:1494 [inline] > __se_sys_bind+0x8d/0xb0 net/socket.c:1492 > ================================================================== > > Crash log2 > ================================================================== > BUG: KMSAN: uninit-value in selinux_socket_connect_helper+0x55c/0x960 > security/selinux/hooks.c:4775 > CPU: 0 PID: 8234 Comm: syz-executor2 Not tainted 4.19.0-rc8+ #18 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0x305/0x460 lib/dump_stack.c:113 > kmsan_report+0x1a2/0x2e0 mm/kmsan/kmsan.c:917 > __msan_warning+0x7d/0xe0 mm/kmsan/kmsan_instr.c:500 > selinux_socket_connect_helper+0x55c/0x960 security/selinux/hooks.c:4775 > selinux_socket_connect+0xbe/0x180 security/selinux/hooks.c:4834 > security_socket_connect+0x127/0x200 security/security.c:1395 > __sys_connect+0x577/0x850 net/socket.c:1660 > __do_sys_connect net/socket.c:1675 [inline] > __se_sys_connect+0x8d/0xb0 net/socket.c:1672 > __x64_sys_connect+0x4a/0x70 net/socket.c:1672 > do_syscall_64+0xb8/0x100 arch/x86/entry/common.c:291 > entry_SYSCALL_64_after_hwframe+0x63/0xe7 > RIP: 0033:0x4497b9 > Code: e8 8c 9f 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 > 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d > 01 f0 ff ff 0f 83 9b 6b fc ff c3 66 2e 0f 1f 84 00 00 00 00 > RSP: 002b:00007ff660d67c68 EFLAGS: 00000246 ORIG_RAX: 000000000000002a > RAX: ffffffffffffffda RBX: 00007ff660d686cc RCX: 00000000004497b9 > RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000013 > RBP: 000000000071bea0 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff > R13: 0000000000000ae0 R14: 00000000006e8b80 R15: 00007ff660d68700 > > Local variable description: ----address@__sys_connect > Variable was created at: > __sys_connect+0x89/0x850 net/socket.c:1647 > __do_sys_connect net/socket.c:1675 [inline] > __se_sys_connect+0x8d/0xb0 net/socket.c:1672 > ================================================================== > > We provide a simple patch below to stop them. > There are a few more lines that invoke move_addr_to_kernel(), but the > two of them > (bind and connect) seem to be the only cases to be corrected. > > > diff --git a/net/socket.c b/net/socket.c > index 390a8ec..de0931c2 100644 > --- a/net/socket.c > +++ b/net/socket.c > @@ -1475,7 +1475,7 @@ int __sys_bind(int fd, struct sockaddr __user > *umyaddr, int addrlen) > sock = sockfd_lookup_light(fd, &err, &fput_needed); > if (sock) { > err = move_addr_to_kernel(umyaddr, addrlen, &address); > - if (err >= 0) { > + if (err > 0) { > err = security_socket_bind(sock, > (struct sockaddr > *)&address, > addrlen); > @@ -1653,7 +1653,7 @@ int __sys_connect(int fd, struct sockaddr __user > *uservaddr, int addrlen) > if (!sock) > goto out; > err = move_addr_to_kernel(uservaddr, addrlen, &address); > - if (err < 0) > + if (err <= 0) > goto out_put; > > err = I believe a better fix would be to add an |addrlen| check to selinux_socket_bind(), which is illegally assuming |address->sa_family| contains any reasonable data regardless of actual address length. I suspect the bug has been introduced in https://github.com/torvalds/linux/commit/0f8db8cc73df60b3de9a5eebd8f117b56eff5b03 > > Thanks, > Kyungtae Kim > > -- > You received this message because you are subscribed to the Google Groups > "syzkaller" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to syzkaller+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout.
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