overlayfs: workdir and upperdir must reside under the same mount
==================================================================
BUG: KASAN: vmalloc-out-of-bounds in __mkroute_output net/ipv4/route.c:2649 [inline]
BUG: KASAN: vmalloc-out-of-bounds in ip_route_output_key_hash_rcu+0xe98/0x1dfc net/ipv4/route.c:2875
Read of size 8 at addr ffff80010c42d000 by task syz.3.44/6900

CPU: 0 UID: 60929 PID: 6900 Comm: syz.3.44 Not tainted syzkaller #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 print_address_description+0xa8/0x238 mm/kasan/report.c:378
 print_report+0x68/0x84 mm/kasan/report.c:482
 kasan_report+0xb0/0x110 mm/kasan/report.c:595
 __asan_report_load8_noabort+0x20/0x2c mm/kasan/report_generic.c:381
 __mkroute_output net/ipv4/route.c:2649 [inline]
 ip_route_output_key_hash_rcu+0xe98/0x1dfc net/ipv4/route.c:2875
 ip_route_output_key_hash+0x154/0x260 net/ipv4/route.c:2705
 __ip_route_output_key include/net/route.h:169 [inline]
 ip_route_output_flow+0x3c/0x160 net/ipv4/route.c:2932
 raw_sendmsg+0xcb0/0x13d4 net/ipv4/raw.c:628
 inet_sendmsg+0x154/0x284 net/ipv4/af_inet.c:859
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0x490/0x7c4 net/socket.c:2592
 ___sys_sendmsg+0x204/0x278 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __arm64_sys_sendmsg+0x184/0x238 net/socket.c:2681
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0xe8/0x23c arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x5c/0x26c arch/arm64/kernel/entry-common.c:724
 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:743
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

The buggy address belongs to a vmalloc virtual mapping
Memory state around the buggy address:
 ffff80010c42cf00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffff80010c42cf80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>ffff80010c42d000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
                   ^
 ffff80010c42d080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffff80010c42d100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
==================================================================
Unable to handle kernel paging request at virtual address ffff80010c42d000
KASAN: probably user-memory-access in range [0x0000000862168000-0x0000000862168007]
Mem abort info:
  ESR = 0x0000000096000005
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x05: level 1 translation fault
Data abort info:
  ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000
  CM = 0, WnR = 0, TnD = 0, TagAccess = 0
  GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000206d55000
[ffff80010c42d000] pgd=0000000000000000, p4d=100000020f59c003, pud=0000000000000000
Internal error: Oops: 0000000096000005 [#1]  SMP
Modules linked in:
CPU: 1 UID: 60929 PID: 6900 Comm: syz.3.44 Tainted: G    B               syzkaller #0 PREEMPT 
Tainted: [B]=BAD_PAGE
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025
pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : __mkroute_output net/ipv4/route.c:2649 [inline]
pc : ip_route_output_key_hash_rcu+0xe98/0x1dfc net/ipv4/route.c:2875
lr : __mkroute_output net/ipv4/route.c:2649 [inline]
lr : ip_route_output_key_hash_rcu+0xe98/0x1dfc net/ipv4/route.c:2875
sp : ffff8000a09a7330
x29: ffff8000a09a7380 x28: dfff800000000000 x27: ffff0000d92e2b00
x26: 0000000080000000 x25: ffff0000d0755c00 x24: 0000000000000000
x23: ffff0000d7a5e520 x22: ffff80010c42d000 x21: ffff0000dd5f2000
x20: 0000000000000001 x19: 0000000000000000 x18: 1fffe0003377d090
x17: ffff80008f86e000 x16: ffff800082e5e68c x15: 0000000000000001
x14: 1ffff0001261fd18 x13: 0000000000000000 x12: 0000000000000000
x11: 0000000000080000 x10: 0000000000009369 x9 : 0000000000000000
x8 : ffff0000cf2f1c80 x7 : 0000000000000000 x6 : ffff80008049ea88
x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffff8000803c8c30
x2 : 0000000000000001 x1 : 0000000000000000 x0 : 0000000000000001
Call trace:
 __mkroute_output net/ipv4/route.c:2649 [inline] (P)
 ip_route_output_key_hash_rcu+0xe98/0x1dfc net/ipv4/route.c:2875 (P)
 ip_route_output_key_hash+0x154/0x260 net/ipv4/route.c:2705
 __ip_route_output_key include/net/route.h:169 [inline]
 ip_route_output_flow+0x3c/0x160 net/ipv4/route.c:2932
 raw_sendmsg+0xcb0/0x13d4 net/ipv4/raw.c:628
 inet_sendmsg+0x154/0x284 net/ipv4/af_inet.c:859
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0x490/0x7c4 net/socket.c:2592
 ___sys_sendmsg+0x204/0x278 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __arm64_sys_sendmsg+0x184/0x238 net/socket.c:2681
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0xe8/0x23c arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x5c/0x26c arch/arm64/kernel/entry-common.c:724
 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:743
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
Code: 387c6908 34000068 aa1603e0 97a0e6f8 (f94002d6) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	387c6908 	ldrb	w8, [x8, x28]
   4:	34000068 	cbz	w8, 0x10
   8:	aa1603e0 	mov	x0, x22
   c:	97a0e6f8 	bl	0xfffffffffe839bec
* 10:	f94002d6 	ldr	x22, [x22] <-- trapping instruction