Re: [syzbot] [mm?] [gfs2?] WARNING in read_rindex_entry

["Zi Yan" <ziy@nvidia.com>]

On Wed Aug 19, 2026 at 8:14 PM EDT, Andrew Morton wrote:
> On Wed, 19 Aug 2026 15:49:42 -0700 syzbot <syzbot+9d20c3ad7d29227de28d@syzkaller.appspotmail.com> wrote:
>
>> Hello,
>> 
>> syzbot found the following issue on:
>> 
>> HEAD commit:    15ef2f78c49d Merge tag 'input-for-v7.2-rc7' of git://git.k..
>> git tree:       upstream
>> console+strace: https://syzkaller.appspot.com/x/log.txt?x=10871279580000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=a0fdc3b566746377
>> dashboard link: https://syzkaller.appspot.com/bug?extid=9d20c3ad7d29227de28d
>> compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14871279580000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=100d2a25580000
>> 
>> Downloadable assets:
>> disk image: https://storage.googleapis.com/syzbot-assets/c2a8c7d3a889/disk-15ef2f78.raw.xz
>> vmlinux: https://storage.googleapis.com/syzbot-assets/2da78afed345/vmlinux-15ef2f78.xz
>> kernel image: https://storage.googleapis.com/syzbot-assets/c4ffd97e4708/bzImage-15ef2f78.xz
>> mounted in repro: https://storage.googleapis.com/syzbot-assets/eaa4120812b6/mount_0.gz
>>   fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=17f52a25580000)
>> 
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+9d20c3ad7d29227de28d@syzkaller.appspotmail.com
>
> Thanks.  Mounting an intentionally corrupted fs image, I assume.
>
> It appears that GFS2 forgot to validate the `ri_length' which it read
> from disk.  That gets used in compute_bitstructs()->kzalloc_objs() and
> the memory allocator didn't like the excessively-sized allocation
> attempt.

+Vlastimil

This makes me question my recent patch[1] that returns NULL for kmalloc
sizes bigger than KMALLOC_MAX_SIZE. It masks this issue.

Probably, we should use __GFP_NOWARN for the GadgetFS warn[2] like
Andrew suggested, since the caller does not care the NULL from kmalloc()
is caused by invalid input or ENOMEM.

For this one, GFS2 needs to validate the ri_length.


[1] https://lore.kernel.org/all/20260817-limit_kmalloc_size-v1-1-5bef487701cc@nvidia.com/
[2] https://lore.kernel.org/all/6a820ebc.9ebadd4d.20b15e.001b.GAE@google.com/
>
>> gfs2: fsid=.: Now mounting FS (format 1801)...
>> gfs2: fsid=..0: journal 0 mapped with 18 extents in 0ms
>> gfs2: fsid=..0: first mount done, others may mount
>> ------------[ cut here ]------------
>> 1
>> WARNING: mm/page_alloc.c:5280 at __alloc_frozen_pages_noprof+0x2427/0x2dc0 mm/page_alloc.c:5280, CPU#1: syz-executor256/5629
>> Modules linked in:
>> CPU: 1 UID: 0 PID: 5629 Comm: syz-executor256 Not tainted syzkaller #0 PREEMPT(full) 
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
>> RIP: 0010:__alloc_frozen_pages_noprof+0x2427/0x2dc0 mm/page_alloc.c:5280
>> Code: e9 8d fb ff ff 31 d2 be 28 12 00 00 48 c7 c7 a0 64 e1 8b e8 5b 8c 69 ff 2e 2e 2e 31 c0 e9 02 ed ff ff c6 05 54 c1 9d 0e 01 90 <0f> 0b 90 e9 6f df ff ff 48 c7 c7 80 ae d3 8e 45 89 f7 44 8b 74 24
>> RSP: 0018:ffffc9000345f0e0 EFLAGS: 00010246
>> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
>> RDX: 0000000000000000 RSI: 1ffff9200068be36 RDI: 0000000000040d40
>> RBP: 000000000000000b R08: 0000000000000005 R09: 0000000000000009
>> R10: 000000000000000b R11: 0000000000000000 R12: 0000000000040d40
>> R13: 1ffff9200068be74 R14: ffffffff9b759444 R15: 0000000000000001
>> FS:  000055556d263400(0000) GS:ffff888123ee1000(0000) knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 000055886dbe9978 CR3: 000000003394d000 CR4: 0000000000350ef0
>> Call Trace:
>>  <TASK>
>>  alloc_pages_mpol+0x1fb/0x540 mm/mempolicy.c:2490
>>  ___kmalloc_large_node+0xe5/0x120 mm/slub.c:5274
>>  __kmalloc_large_node_noprof+0x1c/0x70 mm/slub.c:5305
>>  __do_kmalloc_node mm/slub.c:5322 [inline]
>>  __kmalloc_noprof+0x5a1/0x820 mm/slub.c:5359
>>  _kmalloc_noprof include/linux/slab.h:992 [inline]
>>  _kzalloc_noprof include/linux/slab.h:1309 [inline]
>>  compute_bitstructs fs/gfs2/rgrp.c:766 [inline]
>>  read_rindex_entry+0x4a1/0x1250 fs/gfs2/rgrp.c:931
>>  gfs2_ri_update+0x6f/0x3b0 fs/gfs2/rgrp.c:1001
>>  gfs2_rindex_update+0x40b/0x480 fs/gfs2/rgrp.c:1051
>>  init_inodes+0x1f78/0x2790 fs/gfs2/ops_fstype.c:872
>>  gfs2_fill_super+0x1d3d/0x2cf0 fs/gfs2/ops_fstype.c:1250
>>  get_tree_bdev_flags+0x38c/0x620 fs/super.c:1640
>>  gfs2_get_tree+0x4e/0x280 fs/gfs2/ops_fstype.c:1332
>>  vfs_get_tree+0x92/0x320 fs/super.c:1700
>>  fc_mount fs/namespace.c:1198 [inline]
>>  do_new_mount_fc fs/namespace.c:3765 [inline]
>>  do_new_mount fs/namespace.c:3841 [inline]
>>  path_mount+0x7d0/0x23d0 fs/namespace.c:4161
>>  do_mount fs/namespace.c:4174 [inline]
>>  __do_sys_mount fs/namespace.c:4390 [inline]
>>  __se_sys_mount fs/namespace.c:4367 [inline]
>>  __x64_sys_mount+0x293/0x310 fs/namespace.c:4367
>>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>>  do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
>>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
>> RIP: 0033:0x7ff9e8de99ea
>> Code: 56 53 b8 9d 00 00 00 0f 05 83 f8 ea 75 a2 c7 05 a4 30 0a 00 00 00 00 00 eb 96 e8 51 05 00 00 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 d8 ff ff ff f7 d8 64 89 01 48
>> RSP: 002b:00007ffc770eecc8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
>> RAX: ffffffffffffffda RBX: 00007ffc770eece0 RCX: 00007ff9e8de99ea
>> RDX: 0000200000000040 RSI: 0000200000000100 RDI: 00007ffc770eece0
>> RBP: 0000200000000100 R08: 00007ffc770eed20 R09: 0000000000000000
>> R10: 0000000000008cd3 R11: 0000000000000246 R12: 0000200000000040
>> R13: 0000000000000004 R14: 0000000000000003 R15: 00007ffc770eed20
>>  </TASK>
>> 
>> 
>> ---
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-- 
Best Regards,
Yan, Zi