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BUG: KASAN: stack-out-of-bounds in rds_rdma_bytes net/rds/send.c:1013 [inline]
BUG: KASAN: stack-out-of-bounds in rds_sendmsg+0x1f02/0x1f90 net/rds/send.c:1066
Read of size 8 at addr ffff8801d489fb70 by task syz-executor5/11493

CPU: 1 PID: 11493 Comm: syz-executor5 Not tainted 4.15.0-rc4-mm1+ #49
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
handle_userfault: 17 callbacks suppressed
FAULT_FLAG_ALLOW_RETRY missing 30
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:355 [inline]
 kasan_report+0x23b/0x360 mm/kasan/report.c:413
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:434
 rds_rdma_bytes net/rds/send.c:1013 [inline]
 rds_sendmsg+0x1f02/0x1f90 net/rds/send.c:1066
 sock_sendmsg_nosec net/socket.c:628 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:638
 ___sys_sendmsg+0x320/0x8b0 net/socket.c:2018
 __sys_sendmmsg+0x1ee/0x620 net/socket.c:2108
 SYSC_sendmmsg net/socket.c:2139 [inline]
 SyS_sendmmsg+0x35/0x60 net/socket.c:2134
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x452ac9
RSP: 002b:00007f555aa3bc58 EFLAGS: 00000212 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452ac9
RDX: 0000000000000001 RSI: 0000000020573000 RDI: 0000000000000013
RBP: 0000000000000020 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006ed3a0
R13: 00000000ffffffff R14: 00007f555aa3c6d4 R15: 0000000000000000

CPU: 0 PID: 11472 Comm: syz-executor1 Not tainted 4.15.0-rc4-mm1+ #49
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 handle_userfault+0xbd9/0x2500 fs/userfaultfd.c:430
 do_anonymous_page mm/memory.c:3131 [inline]
 handle_pte_fault mm/memory.c:3945 [inline]
 __handle_mm_fault+0x32a3/0x3ce0 mm/memory.c:4071
 handle_mm_fault+0x38f/0x930 mm/memory.c:4108
 __do_page_fault+0x5c9/0xc90 arch/x86/mm/fault.c:1429
 do_page_fault+0xee/0x720 arch/x86/mm/fault.c:1504
 page_fault+0x2c/0x60 arch/x86/entry/entry_64.S:1243
RIP: 0010:do_strncpy_from_user lib/strncpy_from_user.c:45 [inline]
RIP: 0010:strncpy_from_user+0x185/0x430 lib/strncpy_from_user.c:118
RSP: 0018:ffff8801cb6efd60 EFLAGS: 00010246
RAX: 0000000000010000 RBX: ffff8801cb6efdf8 RCX: ffffffff8266db43
RDX: 0000000000000000 RSI: ffffc90002c05000 RDI: ffff8801cb6efdc0
RBP: ffff8801cb6efe20 R08: ffff8801dae29600 R09: 0000000000000018
R10: 0000000000000000 R11: ffffed0039228abf R12: 0000000000000fe4
R13: 0000000000000fe4 R14: 0000000020012000 R15: 8080808080808080
 getname_flags+0x10e/0x580 fs/namei.c:149
 getname fs/namei.c:209 [inline]
 user_path_create fs/namei.c:3701 [inline]
 SYSC_mknodat fs/namei.c:3762 [inline]
 SyS_mknodat+0x17a/0x480 fs/namei.c:3750
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x452ac9
RSP: 002b:00007fbca5e19ae8 EFLAGS: 00000217 ORIG_RAX: 0000000000000103
RAX: ffffffffffffffda RBX: 000000000071bf58 RCX: 0000000000452ac9
RDX: 0000000000006000 RSI: 0000000020012000 RDI: 00000000ffffff9c
RBP: 00000000000000ed R08: 0000000000000000 R09: 0000000000000000
R10: 00000000000007c7 R11: 0000000000000217 R12: 00000000006ee6d8
R13: 00000000ffffffff R14: 00007fbca5e1a6d4 R15: 0000000000000019
The buggy address belongs to the page:
page:ffffea00075227c0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: 0000000000000000 ffffea0007520101 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d489fa00: 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 f2
 ffff8801d489fa80: f2 f2 f2 f2 f2 f2 00 00 00 00 00 00 00 00 00 00
>ffff8801d489fb00: 00 00 00 00 00 00 f2 f2 f2 f2 00 00 00 00 04 f2
                                                             ^
 ffff8801d489fb80: f2 f2 f2 f2 f2 f2 00 00 00 00 00 00 00 00 00 00
 ffff8801d489fc00: 00 00 00 00 00 00 f3 f3 f3 f3 00 00 00 00 00 00
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