KASAN: use-after-free Read in sock_i_uid

From: syzbot
Date: Mon Sep 10 2018 - 04:36:07 EST

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Hello,

syzbot found the following crash on:

HEAD commit: 3d0e7a9e00fd Merge tag 'md/4.19-rc2' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1261e98e400000
kernel config: https://syzkaller.appspot.com/x/.config?x=8f59875069d721b6
dashboard link: https://syzkaller.appspot.com/bug?extid=b239ac9b3c007f9cef90
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+b239ac9b3c007f9cef90@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: use-after-free in sock_i_uid+0x9c/0xb0 net/core/sock.c:1910
Read of size 4 at addr ffff8801c4333a34 by task syz-executor2/10612

CPU: 1 PID: 10612 Comm: syz-executor2 Not tainted 4.19.0-rc2+ #6
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+0x1c4/0x2b4 lib/dump_stack.c:113
print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
__asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
sock_i_uid+0x9c/0xb0 net/core/sock.c:1910
tipc_sk_fill_sock_diag+0x3f7/0xd90 net/tipc/socket.c:3317
__tipc_add_sock_diag+0x233/0x360 net/tipc/diag.c:62
tipc_nl_sk_walk+0x122/0x1d0 net/tipc/socket.c:3250
tipc_diag_dump+0x24/0x30 net/tipc/diag.c:73
netlink_dump+0x519/0xd50 net/netlink/af_netlink.c:2233
__netlink_dump_start+0x4f1/0x6f0 net/netlink/af_netlink.c:2329
netlink_dump_start include/linux/netlink.h:213 [inline]
tipc_sock_diag_handler_dump+0x28e/0x3d0 net/tipc/diag.c:91
__sock_diag_cmd net/core/sock_diag.c:232 [inline]
sock_diag_rcv_msg+0x31d/0x410 net/core/sock_diag.c:263
netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2454
sock_diag_rcv+0x2a/0x40 net/core/sock_diag.c:274
netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline]
netlink_unicast+0x5a5/0x760 net/netlink/af_netlink.c:1343
netlink_sendmsg+0xa18/0xfc0 net/netlink/af_netlink.c:1908
sock_sendmsg_nosec net/socket.c:621 [inline]
sock_sendmsg+0xd5/0x120 net/socket.c:631
___sys_sendmsg+0x7fd/0x930 net/socket.c:2114
__sys_sendmsg+0x11d/0x280 net/socket.c:2152
__do_sys_sendmsg net/socket.c:2161 [inline]
__se_sys_sendmsg net/socket.c:2159 [inline]
__x64_sys_sendmsg+0x78/0xb0 net/socket.c:2159
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457099
Code: fd b4 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 b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f5a612d4c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f5a612d56d4 RCX: 0000000000457099
RDX: 0000000000000000 RSI: 0000000020000040 RDI: 0000000000000006
RBP: 0000000000930140 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004d4bc0 R14: 00000000004c910b R15: 0000000000000001

Allocated by task 10609:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
kmem_cache_alloc+0x12e/0x730 mm/slab.c:3554
sock_alloc_inode+0x1d/0x260 net/socket.c:244
alloc_inode+0x63/0x190 fs/inode.c:210
new_inode_pseudo+0x71/0x1a0 fs/inode.c:903
sock_alloc+0x41/0x270 net/socket.c:547
__sock_create+0x175/0x930 net/socket.c:1239
sock_create net/socket.c:1315 [inline]
__sys_socket+0x106/0x260 net/socket.c:1345
__do_sys_socket net/socket.c:1354 [inline]
__se_sys_socket net/socket.c:1352 [inline]
__x64_sys_socket+0x73/0xb0 net/socket.c:1352
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 10609:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kmem_cache_free+0x83/0x290 mm/slab.c:3756
sock_destroy_inode+0x51/0x60 net/socket.c:272
destroy_inode+0x159/0x200 fs/inode.c:267
evict+0x5e0/0x980 fs/inode.c:575
iput_final fs/inode.c:1547 [inline]
iput+0x679/0xa90 fs/inode.c:1573
dentry_unlink_inode+0x461/0x5e0 fs/dcache.c:374
__dentry_kill+0x44c/0x7a0 fs/dcache.c:566
dentry_kill+0xc9/0x5a0 fs/dcache.c:685
dput.part.26+0x660/0x790 fs/dcache.c:846
dput+0x15/0x20 fs/dcache.c:828
__fput+0x4cf/0xa30 fs/file_table.c:291
____fput+0x15/0x20 fs/file_table.c:309
task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
get_signal+0x155e/0x1980 kernel/signal.c:2343
do_signal+0x9c/0x21e0 arch/x86/kernel/signal.c:816
exit_to_usermode_loop+0x2e5/0x380 arch/x86/entry/common.c:162
prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801c4333a00
which belongs to the cache sock_inode_cache of size 984
The buggy address is located 52 bytes inside of
984-byte region [ffff8801c4333a00, ffff8801c4333dd8)
The buggy address belongs to the page:
page:ffffea000710ccc0 count:1 mapcount:0 mapping:ffff8801d9489b40 index:0xffff8801c4333ffd
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea000726fac8 ffffea00074f1b88 ffff8801d9489b40
raw: ffff8801c4333ffd ffff8801c4333100 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801c4333900: fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc
ffff8801c4333980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc

ffff8801c4333a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

^
ffff8801c4333a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801c4333b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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Next message: syzbot: "general protection fault in rhashtable_walk_exit"
Previous message: Dan Carpenter: "[PATCH] RDMA/hns: Fix an error code in hns_roce_v2_init_eq_table()"
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