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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 ffff8801c99ff9e0 by task syz-executor0/3159

CPU: 1 PID: 3159 Comm: syz-executor0 Not tainted 4.15.0-rc4+ #141
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
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 rds_rdma_bytes net/rds/send.c:1013 [inline]
 rds_sendmsg+0x1f02/0x1f90 net/rds/send.c:1066
 sock_sendmsg_nosec net/socket.c:636 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:646
 ___sys_sendmsg+0x320/0x8b0 net/socket.c:2026
 __sys_sendmmsg+0x31b/0x620 net/socket.c:2109
 C_SYSC_sendmmsg net/compat.c:745 [inline]
 compat_SyS_sendmmsg+0x32/0x40 net/compat.c:742
 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
 do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
 entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:125
RIP: 0023:0xf7fbec79
RSP: 002b:00000000ff94cd1c EFLAGS: 00000296 ORIG_RAX: 0000000000000159
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000002020c000
RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:000000009a3a9430 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: 0000000000000000 0000000100000001 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c99ff880: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 f2 f2 f2
 ffff8801c99ff900: f2 f2 f2 f2 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8801c99ff980: 00 00 00 00 f2 f2 f2 f2 00 00 00 00 04 f2 f2 f2
                                                       ^
 ffff8801c99ffa00: f2 f2 f2 f2 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801c99ffa80: 00 00 00 00 f3 f3 f3 f3 00 00 00 00 00 00 00 00
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