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SubjectRe: KMSAN: kernel-infoleak in sctp_getsockopt
On Wed, Dec 5, 2018 at 8:31 PM syzbot
<syzbot+ad5d327e6936a2e284be@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: fffec98ae2a6 net: proper support for CONFIG_GENERIC_CSUM o..
> git tree: https://github.com/google/kmsan.git/master
> console output: https://syzkaller.appspot.com/x/log.txt?x=12e84a47400000
> kernel config: https://syzkaller.appspot.com/x/.config?x=56b48b46dafe4516
> dashboard link: https://syzkaller.appspot.com/bug?extid=ad5d327e6936a2e284be
> compiler: clang version 8.0.0 (trunk 343298)
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=103cd225400000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+ad5d327e6936a2e284be@syzkaller.appspotmail.com
>
> 8021q: adding VLAN 0 to HW filter on device team0
> 8021q: adding VLAN 0 to HW filter on device team0
> 8021q: adding VLAN 0 to HW filter on device team0
> 8021q: adding VLAN 0 to HW filter on device team0
> ==================================================================
> BUG: KMSAN: kernel-infoleak in _copy_to_user+0x19a/0x230 lib/usercopy.c:33
> CPU: 1 PID: 8164 Comm: syz-executor2 Not tainted 4.20.0-rc3+ #95
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
> __dump_stack lib/dump_stack.c:77 [inline]
> dump_stack+0x32d/0x480 lib/dump_stack.c:113
> kmsan_report+0x12c/0x290 mm/kmsan/kmsan.c:683
> kmsan_internal_check_memory+0x32a/0xa50 mm/kmsan/kmsan.c:743
> kmsan_copy_to_user+0x78/0xd0 mm/kmsan/kmsan_hooks.c:634
> _copy_to_user+0x19a/0x230 lib/usercopy.c:33
> copy_to_user include/linux/uaccess.h:183 [inline]
> sctp_getsockopt_local_addrs net/sctp/socket.c:5998 [inline]
> sctp_getsockopt+0x15248/0x186f0 net/sctp/socket.c:7477
> sock_common_getsockopt+0x13f/0x180 net/core/sock.c:2937
> __sys_getsockopt+0x489/0x550 net/socket.c:1939
> __do_sys_getsockopt net/socket.c:1950 [inline]
> __se_sys_getsockopt+0xe1/0x100 net/socket.c:1947
> __x64_sys_getsockopt+0x62/0x80 net/socket.c:1947
> do_syscall_64+0xcf/0x110 arch/x86/entry/common.c:291
> entry_SYSCALL_64_after_hwframe+0x63/0xe7
> RIP: 0033:0x457569
> Code: fd b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f4991886c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
> RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000457569
> RDX: 000000000000006d RSI: 0000000000000084 RDI: 0000000000000003
> RBP: 000000000072bf00 R08: 0000000020000140 R09: 0000000000000000
> R10: 0000000020001100 R11: 0000000000000246 R12: 00007f49918876d4
> R13: 00000000004c7d88 R14: 00000000004ce348 R15: 00000000ffffffff
>
> Uninit was stored to memory at:
> kmsan_save_stack_with_flags mm/kmsan/kmsan.c:246 [inline]
> kmsan_save_stack mm/kmsan/kmsan.c:261 [inline]
> kmsan_internal_chain_origin+0x13d/0x240 mm/kmsan/kmsan.c:469
> kmsan_memcpy_memmove_metadata+0x1a9/0xf70 mm/kmsan/kmsan.c:344
> kmsan_memcpy_metadata+0xb/0x10 mm/kmsan/kmsan.c:362
> __msan_memcpy+0x61/0x70 mm/kmsan/kmsan_instr.c:162
> sctp_copy_laddrs net/sctp/socket.c:5901 [inline]
> sctp_getsockopt_local_addrs net/sctp/socket.c:5967 [inline]
> sctp_getsockopt+0x14f41/0x186f0 net/sctp/socket.c:7477
> sock_common_getsockopt+0x13f/0x180 net/core/sock.c:2937
> __sys_getsockopt+0x489/0x550 net/socket.c:1939
> __do_sys_getsockopt net/socket.c:1950 [inline]
> __se_sys_getsockopt+0xe1/0x100 net/socket.c:1947
> __x64_sys_getsockopt+0x62/0x80 net/socket.c:1947
> do_syscall_64+0xcf/0x110 arch/x86/entry/common.c:291
> entry_SYSCALL_64_after_hwframe+0x63/0xe7
>
> Uninit was stored to memory at:
> kmsan_save_stack_with_flags mm/kmsan/kmsan.c:246 [inline]
> kmsan_save_stack mm/kmsan/kmsan.c:261 [inline]
> kmsan_internal_chain_origin+0x13d/0x240 mm/kmsan/kmsan.c:469
> kmsan_memcpy_memmove_metadata+0x1a9/0xf70 mm/kmsan/kmsan.c:344
> kmsan_memcpy_metadata+0xb/0x10 mm/kmsan/kmsan.c:362
> __msan_memcpy+0x61/0x70 mm/kmsan/kmsan_instr.c:162
> sctp_copy_laddrs net/sctp/socket.c:5890 [inline]
> sctp_getsockopt_local_addrs net/sctp/socket.c:5967 [inline]
> sctp_getsockopt+0x14de8/0x186f0 net/sctp/socket.c:7477
> sock_common_getsockopt+0x13f/0x180 net/core/sock.c:2937
> __sys_getsockopt+0x489/0x550 net/socket.c:1939
> __do_sys_getsockopt net/socket.c:1950 [inline]
> __se_sys_getsockopt+0xe1/0x100 net/socket.c:1947
> __x64_sys_getsockopt+0x62/0x80 net/socket.c:1947
> do_syscall_64+0xcf/0x110 arch/x86/entry/common.c:291
> entry_SYSCALL_64_after_hwframe+0x63/0xe7
>
> Uninit was created at:
> kmsan_save_stack_with_flags mm/kmsan/kmsan.c:246 [inline]
> kmsan_internal_poison_shadow+0x6d/0x130 mm/kmsan/kmsan.c:170
> kmsan_kmalloc+0xa1/0x100 mm/kmsan/kmsan_hooks.c:186
> __kmalloc+0x14c/0x4d0 mm/slub.c:3825
> kmalloc include/linux/slab.h:551 [inline]
> sctp_inet6addr_event+0x60e/0xbd0 net/sctp/ipv6.c:100
> notifier_call_chain kernel/notifier.c:93 [inline]
> __atomic_notifier_call_chain kernel/notifier.c:183 [inline]
> atomic_notifier_call_chain+0x13d/0x240 kernel/notifier.c:193
> inet6addr_notifier_call_chain+0x76/0x90 net/ipv6/addrconf_core.c:107
> ipv6_add_addr+0x2597/0x2890 net/ipv6/addrconf.c:1115
> inet6_addr_add+0xc86/0x1c10 net/ipv6/addrconf.c:2912
> inet6_rtm_newaddr+0x167e/0x3d20 net/ipv6/addrconf.c:4750
> rtnetlink_rcv_msg+0x1148/0x1540 net/core/rtnetlink.c:4947
> netlink_rcv_skb+0x394/0x640 net/netlink/af_netlink.c:2477
> rtnetlink_rcv+0x50/0x60 net/core/rtnetlink.c:4965
> netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
> netlink_unicast+0x1699/0x1740 net/netlink/af_netlink.c:1336
> netlink_sendmsg+0x13c7/0x1440 net/netlink/af_netlink.c:1917
> sock_sendmsg_nosec net/socket.c:621 [inline]
> sock_sendmsg net/socket.c:631 [inline]
> ___sys_sendmsg+0xe3b/0x1240 net/socket.c:2116
> __sys_sendmsg net/socket.c:2154 [inline]
> __do_sys_sendmsg net/socket.c:2163 [inline]
> __se_sys_sendmsg+0x305/0x460 net/socket.c:2161
> __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2161
> do_syscall_64+0xcf/0x110 arch/x86/entry/common.c:291
> entry_SYSCALL_64_after_hwframe+0x63/0xe7
>
> Bytes 32-35 of 2100 are uninitialized
> Memory access of size 2100 starts at ffff888185d8b000
> Data copied to user address 0000000020001108
> ==================================================================
When a network device goes up and sctp_inetaddr_event() is called, it
allocates a partially initialized struct sctp_sockaddr_entry to hold
the newly created address.
The attached reproducer can be then used to read up to 8 uninit bytes
for each of the local addresses.
I guess the devices aren't created so often that this can pose any
security risk, but we probably still need to allocate this structure
with __GFP_ZERO.
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches
>
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--
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
#ifndef DUMP_BUF_H
#define DUMP_BUF_H

#ifndef DUMP_MIN_STRLEN
#define DUMP_MIN_STRLEN 1
#endif

#ifndef DUMP_PARALLEL
#define DUMP_PARALLEL 0
#endif

#ifndef DUMP_PRINT_BUF_ADDR
#define DUMP_PRINT_BUF_ADDR 0
#endif

#ifndef DUMP_PRINT_HEX
#define DUMP_PRINT_HEX 0
#endif

#ifndef DUMP_PRINT_STRING
#define DUMP_PRINT_STRING 0
#endif

#if DUMP_PARALLEL
pthread_mutex_t out_mutex = PTHREAD_MUTEX_INITIALIZER;
#endif

void dump_buf(unsigned char *buf, int len) {
int i, nz = 0;
for (i = 0; i < len; i++) {
if (buf[i]) {
nz = 1;
break;
}
}
if (!nz) {
// The buffer is empty.
return;
} else {
#if DUMP_PARALLEL
pthread_mutex_lock(&out_mutex);
#endif
#if DUMP_PRINT_BUF_ADDR
fprintf(stderr, "nonempty buffer at %p\n", buf);
#endif
#if DUMP_PRINT_HEX
for (i=0; i < len; i++) {
if (buf[i]) {
fprintf(stderr, "buf[%d]: %x (%p)\n", i, buf[i], *(void**)&buf[i]);
}
}
#endif // DUMP_PRINT_HEX
#if DUMP_PARALLEL
pthread_mutex_unlock(&out_mutex);
#endif
}
#if DUMP_PARALLEL
pthread_mutex_lock(&out_mutex);
#endif
#if DUMP_PRINT_STRING
for (i = 0; i < len; i++) {
if (buf[i]) {
int str_len = strlen(&buf[i]);
// Short string pieces are too boring.
if (str_len >= DUMP_MIN_STRLEN) {
unsigned char *c;
for (c = &buf[i]; c < &buf[i + str_len]; c++) {
if ((*c > 127) || ((*c < 32) && (*c != 10) && (*c != 13))) {
*c = ' ';
continue;
}
}
// Dump the buffer.
fprintf(stderr, "%s\n", &buf[i]);
}
i += str_len;
}
}
#endif // DUMP_PRINT_STRING
#if DUMP_PARALLEL
pthread_mutex_unlock(&out_mutex);
#endif
}

#endif
#include <stdio.h>
#include <pthread.h>
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
#include <unistd.h>

#define DUMP_PARALLEL 1
#define DUMP_PRINT_BUF_ADDR 1
#define DUMP_PRINT_STRING 1
#define DUMP_PRINT_HEX 1
#include "dump_buf.h"

void *setsockopt_fn(void *arg) {
int sock = (int)arg;
struct sockaddr addr;
memset(&addr, 0, sizeof(addr));
addr.sa_family = 2;
addr.sa_data[2] = 0xac;
addr.sa_data[3] = 0x14;
addr.sa_data[4] = 0x14;
setsockopt(sock, 0x84, 0x6e, &addr, 0x10);
}

#define BUFLEN (0x2c2)
void *getsockopt_fn(void *arg) {
int sock = (int)arg;
char buf[BUFLEN];
memset(buf, 0, BUFLEN);
int socklen = BUFLEN;
getsockopt(sock, 0x84, /*SCTP_GET_LOCAL_ADDRS*/0x6d, buf, &socklen);
dump_buf(&(buf[8]), 32);
}

void do_work(int sock) {
pthread_t t1, t2;
for (int i = 0; i < 10; i++) {
pthread_create(&t1, NULL, getsockopt_fn, (void*)sock);
pthread_create(&t2, NULL, setsockopt_fn, (void*)sock);
usleep(100);
}
}

int main(int argc, char *argv[]) {
int res;
int pid = fork();
if (pid == 0) {
int sock = socket(0x2, 0x1, 0x84);
do_work(sock);
}
sleep(10);
return 0;
}
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