In the Linux kernel, the following vulnerability has been resolved: mm/vmscan: fix a bug calling wakeup_kswapd() with a wrong zone index W

In the Linux kernel, the following vulnerability has been resolved:

mm/vmscan: fix a bug calling wakeup_kswapd() with a wrong zone index

With numa balancing on, when a numa system is running where a numa node
doesn't have its local memory so it has no managed zones, the following
oops has been observed. It's because wakeup_kswapd() is called with a
wrong zone index, -1. Fixed it by checking the index before calling
wakeup_kswapd().

BUG: unable to handle page fault for address: 00000000000033f3
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP NOPTI
CPU: 2 PID: 895 Comm: masim Not tainted 6.6.0-dirty #255
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
RIP: 0010:wakeup_kswapd (./linux/mm/vmscan.c:7812)
Code: (omitted)
RSP: 0000:ffffc90004257d58 EFLAGS: 00010286
RAX: ffffffffffffffff RBX: ffff88883fff0480 RCX: 0000000000000003
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88883fff0480
RBP: ffffffffffffffff R08: ff0003ffffffffff R09: ffffffffffffffff
R10: ffff888106c95540 R11: 0000000055555554 R12: 0000000000000003
R13: 0000000000000000 R14: 0000000000000000 R15: ffff88883fff0940
FS: 00007fc4b8124740(0000) GS:ffff888827c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000000033f3 CR3: 000000026cc08004 CR4: 0000000000770ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
<TASK>
? __die
? page_fault_oops
? __pte_offset_map_lock
? exc_page_fault
? asm_exc_page_fault
? wakeup_kswapd
migrate_misplaced_page
__handle_mm_fault
handle_mm_fault
do_user_addr_fault
exc_page_fault
asm_exc_page_fault
RIP: 0033:0x55b897ba0808
Code: (omitted)
RSP: 002b:00007ffeefa821a0 EFLAGS: 00010287
RAX: 000055b89983acd0 RBX: 00007ffeefa823f8 RCX: 000055b89983acd0
RDX: 00007fc2f8122010 RSI: 0000000000020000 RDI: 000055b89983acd0
RBP: 00007ffeefa821a0 R08: 0000000000000037 R09: 0000000000000075
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00007ffeefa82410 R14: 000055b897ba5dd8 R15: 00007fc4b8340000
</TASK>