[syzbot] [mm?] [io-uring?] WARNING in get_pte_pfn

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0e389834672c Merge tag 'for-6.7-rc5-tag' of git://git.kern..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1454824ee80000
kernel config: https://syzkaller.appspot.com/x/.config?x=f21aff374937e60e
dashboard link: https://syzkaller.appspot.com/bug?extid=03fd9b3f71641f0ebf2d
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13b4ef49e80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=118314d6e80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e58cd74e152a/disk-0e389834.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/45d17ccb34bc/vmlinux-0e389834.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b9b7105d4e08/bzImage-0e389834.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+03fd9b...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 5066 at mm/vmscan.c:3242 get_pte_pfn+0x1b5/0x3f0 mm/vmscan.c:3242
Modules linked in:
CPU: 1 PID: 5066 Comm: syz-executor668 Not tainted 6.7.0-rc5-syzkaller-00270-g0e389834672c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
RIP: 0010:get_pte_pfn+0x1b5/0x3f0 mm/vmscan.c:3242
Code: f3 74 2a e8 6d 78 cb ff 31 ff 48 b8 00 00 00 00 00 00 00 02 48 21 c5 48 89 ee e8 e6 73 cb ff 48 85 ed 74 4e e8 4c 78 cb ff 90 <0f> 0b 90 48 c7 c3 ff ff ff ff e8 3c 78 cb ff 48 b8 00 00 00 00 00
RSP: 0018:ffffc900041e6878 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 000000000007891d RCX: ffffffff81bbf6e3
RDX: ffff88807d813b80 RSI: ffffffff81bbf684 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000200 R11: 0000000000000003 R12: 0000000000000200
R13: 1ffff9200083cd0f R14: 0000000000010b21 R15: 0000000020ffc000
FS: 0000555555f4d480(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000005fbfa000 CR4: 0000000000350ef0
Call Trace:
<TASK>
lru_gen_look_around+0x70d/0x11a0 mm/vmscan.c:4001
folio_referenced_one+0x5a2/0xf70 mm/rmap.c:843
rmap_walk_anon+0x225/0x570 mm/rmap.c:2485
rmap_walk mm/rmap.c:2562 [inline]
rmap_walk mm/rmap.c:2557 [inline]
folio_referenced+0x28a/0x4b0 mm/rmap.c:960
folio_check_references mm/vmscan.c:829 [inline]
shrink_folio_list+0x1ace/0x3f00 mm/vmscan.c:1160
evict_folios+0x6e7/0x1b90 mm/vmscan.c:4499
try_to_shrink_lruvec+0x638/0xa10 mm/vmscan.c:4704
lru_gen_shrink_lruvec mm/vmscan.c:4849 [inline]
shrink_lruvec+0x314/0x2990 mm/vmscan.c:5622
shrink_node_memcgs mm/vmscan.c:5842 [inline]
shrink_node+0x811/0x3710 mm/vmscan.c:5877
shrink_zones mm/vmscan.c:6116 [inline]
do_try_to_free_pages+0x36c/0x1940 mm/vmscan.c:6178
try_to_free_mem_cgroup_pages+0x31a/0x770 mm/vmscan.c:6493
try_charge_memcg+0x3d3/0x11f0 mm/memcontrol.c:2742
obj_cgroup_charge_pages mm/memcontrol.c:3255 [inline]
__memcg_kmem_charge_page+0xdd/0x2a0 mm/memcontrol.c:3281
__alloc_pages+0x263/0x2420 mm/page_alloc.c:4585
alloc_pages_mpol+0x258/0x5f0 mm/mempolicy.c:2133
__get_free_pages+0xc/0x40 mm/page_alloc.c:4615
io_mem_alloc+0x33/0x60 io_uring/io_uring.c:2789
io_allocate_scq_urings io_uring/io_uring.c:3842 [inline]
io_uring_create io_uring/io_uring.c:4019 [inline]
io_uring_setup+0x13ed/0x2430 io_uring/io_uring.c:4131
__do_sys_io_uring_setup io_uring/io_uring.c:4158 [inline]
__se_sys_io_uring_setup io_uring/io_uring.c:4152 [inline]
__x64_sys_io_uring_setup+0x98/0x140 io_uring/io_uring.c:4152
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f4b0e4778a9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 d1 1a 00 00 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff814fe868 EFLAGS: 00000202 ORIG_RAX: 00000000000001a9
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f4b0e4778a9
RDX: 0000000020000700 RSI: 0000000020000640 RDI: 0000000000005a19
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000020000700
R10: 00007fff814fe8d0 R11: 0000000000000202 R12: 0000000020000640
R13: 0000000000000000 R14: 0000000000005a19 R15: 0000000020000700
</TASK>


---
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[Jens Axboe]

Don't think this is io_uring related, test case looks like it's just
setting up and tearing down big rings.

--
Jens Axboe

[Yu Zhao]

#syz test

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9dd8977de5a2..041f9ad8f95b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3230,7 +3230,8 @@ static bool get_next_vma(unsigned long mask, unsigned long size, struct mm_walk
return false;
}

-static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned long addr)
+static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned long addr,
+ struct page *page)
{
unsigned long pfn = pte_pfn(pte);

@@ -3239,8 +3240,14 @@ static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned
if (!pte_present(pte) || is_zero_pfn(pfn))
return -1;

- if (WARN_ON_ONCE(pte_devmap(pte) || pte_special(pte)))
+ if (pte_devmap(pte) || pte_special(pte)) {
+ if (page)
+ dump_page(page, "get_pte_pfn()");
+ dump_vma(vma);
+ dump_mm(vma->vm_mm);
+ BUG();
return -1;
+ }

if (WARN_ON_ONCE(!pfn_valid(pfn)))
return -1;
@@ -3331,7 +3338,7 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end,
total++;
walk->mm_stats[MM_LEAF_TOTAL]++;

- pfn = get_pte_pfn(ptent, args->vma, addr);
+ pfn = get_pte_pfn(ptent, args->vma, addr, NULL);
if (pfn == -1)
continue;

@@ -3998,7 +4005,7 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
unsigned long pfn;
pte_t ptent = ptep_get(pte + i);

- pfn = get_pte_pfn(ptent, pvmw->vma, addr);
+ pfn = get_pte_pfn(ptent, pvmw->vma, addr, pfn_to_page(pvmw->pfn));
if (pfn == -1)
continue;

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
kernel BUG in get_pte_pfn

ioctx_table 0000000000000000
owner ffff8880208f3b80 exe_file ffff88801a7ff180
notifier_subscriptions 0000000000000000
numa_next_scan 4294946352 numa_scan_offset 0 numa_scan_seq 0
tlb_flush_pending 0
def_flags: 0x0()
------------[ cut here ]------------
kernel BUG at mm/vmscan.c:3248!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 5911 Comm: syz-executor.0 Not tainted 6.7.0-rc6-syzkaller-00248-g5254c0cbc92d-dirty #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023

RIP: 0010:get_pte_pfn+0x3ec/0x450 mm/vmscan.c:3248
Code: ef e8 48 27 0a 00 49 8d 7d 10 b8 ff ff 37 00 48 89 fa 48 c1 e0 2a 48 c1 ea 03 80 3c 02 00 75 5a 49 8b 7d 10 e8 c5 29 0a 00 90 <0f> 0b 4c 89 ef e8 fa 0f 22 00 e9 dc fc ff ff 48 c7 c7 80 43 19 8f
RSP: 0018:ffffc9000bb4e868 EFLAGS: 00010286
RAX: 0000000000000331 RBX: ffffea0001fb0240 RCX: ffffffff816a6559
RDX: 0000000000000000 RSI: ffffffff816aea02 RDI: 0000000000000005

RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000

R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000200
R13: ffff88807ba95e00 R14: 1ffff92001769d0e R15: 0000000000010b22
FS: 00007ff14dc496c0(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000000000000000 CR3: 0000000076e1e000 CR4: 0000000000350ef0
Call Trace:
<TASK>
lru_gen_look_around+0x743/0x11f0 mm/vmscan.c:4008

folio_referenced_one+0x5a2/0xf70 mm/rmap.c:843
rmap_walk_anon+0x225/0x570 mm/rmap.c:2485
rmap_walk mm/rmap.c:2562 [inline]
rmap_walk mm/rmap.c:2557 [inline]
folio_referenced+0x28a/0x4b0 mm/rmap.c:960
folio_check_references mm/vmscan.c:829 [inline]
shrink_folio_list+0x1ace/0x3f00 mm/vmscan.c:1160

evict_folios+0x6e7/0x1b90 mm/vmscan.c:4506
try_to_shrink_lruvec+0x638/0xa10 mm/vmscan.c:4711
lru_gen_shrink_lruvec mm/vmscan.c:4856 [inline]
shrink_lruvec+0x314/0x2990 mm/vmscan.c:5629
shrink_node_memcgs mm/vmscan.c:5849 [inline]
shrink_node+0x811/0x3710 mm/vmscan.c:5884
shrink_zones mm/vmscan.c:6123 [inline]
do_try_to_free_pages+0x36c/0x1940 mm/vmscan.c:6185
try_to_free_mem_cgroup_pages+0x31a/0x770 mm/vmscan.c:6500

try_charge_memcg+0x3d3/0x11f0 mm/memcontrol.c:2742
obj_cgroup_charge_pages mm/memcontrol.c:3255 [inline]
__memcg_kmem_charge_page+0xdd/0x2a0 mm/memcontrol.c:3281
__alloc_pages+0x263/0x2420 mm/page_alloc.c:4585
alloc_pages_mpol+0x258/0x5f0 mm/mempolicy.c:2133
__get_free_pages+0xc/0x40 mm/page_alloc.c:4615
io_mem_alloc+0x33/0x60 io_uring/io_uring.c:2789
io_allocate_scq_urings io_uring/io_uring.c:3842 [inline]
io_uring_create io_uring/io_uring.c:4019 [inline]
io_uring_setup+0x13ed/0x2430 io_uring/io_uring.c:4131
__do_sys_io_uring_setup io_uring/io_uring.c:4158 [inline]
__se_sys_io_uring_setup io_uring/io_uring.c:4152 [inline]
__x64_sys_io_uring_setup+0x98/0x140 io_uring/io_uring.c:4152
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

RIP: 0033:0x7ff14ce7cba9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 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 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff14dc49058 EFLAGS: 00000206 ORIG_RAX: 00000000000001a9
RAX: ffffffffffffffda RBX: 00007ff14cf9bf80 RCX: 00007ff14ce7cba9

RDX: 0000000020000700 RSI: 0000000020000640 RDI: 0000000000005a19

RBP: 00007ff14cec847a R08: 0000000000000000 R09: 0000000020000700
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000020000640

R13: 0000000000000000 R14: 0000000000005a19 R15: 0000000020000700
</TASK>

Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:get_pte_pfn+0x3ec/0x450 mm/vmscan.c:3248
Code: ef e8 48 27 0a 00 49 8d 7d 10 b8 ff ff 37 00 48 89 fa 48 c1 e0 2a 48 c1 ea 03 80 3c 02 00 75 5a 49 8b 7d 10 e8 c5 29 0a 00 90 <0f> 0b 4c 89 ef e8 fa 0f 22 00 e9 dc fc ff ff 48 c7 c7 80 43 19 8f
RSP: 0018:ffffc9000bb4e868 EFLAGS: 00010286
RAX: 0000000000000331 RBX: ffffea0001fb0240 RCX: ffffffff816a6559
RDX: 0000000000000000 RSI: ffffffff816aea02 RDI: 0000000000000005

RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000

R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000200
R13: ffff88807ba95e00 R14: 1ffff92001769d0e R15: 0000000000010b22
FS: 00007ff14dc496c0(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000000000000000 CR3: 0000000076e1e000 CR4: 0000000000350ef0


Tested on:

commit: 5254c0cb Merge tag 'block-6.7-2023-12-22' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1709d481e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=314e9ad033a7d3a7

dashboard link: https://syzkaller.appspot.com/bug?extid=03fd9b3f71641f0ebf2d
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=1120ad76e80000

[Yu Zhao]

Can confirm it is an MM bug. Just posted the fix:
https://lore.kernel.org/20231223045647....@google.com/