Re: [syzbot] [mm?] WARNING in __folio_rmap_sanity_checks

[David Hildenbrand <david@redhat.com>]

On 03.01.24 12:48, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    ab0b3e6ef50d Add linux-next specific files for 20240102
> git tree:       linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=17be3e09e80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=a14a6350374945f9
> dashboard link: https://syzkaller.appspot.com/bug?extid=50ef73537bbc393a25bb
> 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=14e2256ee80000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17b57db5e80000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/4e6376fe5764/disk-ab0b3e6e.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/7cb9ecbaf001/vmlinux-ab0b3e6e.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/2c1a9a6d424f/bzImage-ab0b3e6e.xz
> 
> The issue was bisected to:
> 
> commit 68f0320824fa59c5429cbc811e6c46e7a30ea32c
> Author: David Hildenbrand <david@redhat.com>
> Date:   Wed Dec 20 22:44:31 2023 +0000
> 
>      mm/rmap: convert folio_add_file_rmap_range() into folio_add_file_rmap_[pte|ptes|pmd]()
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10b9e1b1e80000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=12b9e1b1e80000
> console output: https://syzkaller.appspot.com/x/log.txt?x=14b9e1b1e80000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+50ef73537bbc393a25bb@syzkaller.appspotmail.com
> Fixes: 68f0320824fa ("mm/rmap: convert folio_add_file_rmap_range() into folio_add_file_rmap_[pte|ptes|pmd]()")
> 
>   kasan_quarantine_reduce+0x18e/0x1d0 mm/kasan/quarantine.c:283
>   __kasan_slab_alloc+0x65/0x90 mm/kasan/common.c:324
>   kasan_slab_alloc include/linux/kasan.h:201 [inline]
>   slab_post_alloc_hook mm/slub.c:3813 [inline]
>   slab_alloc_node mm/slub.c:3860 [inline]
>   kmem_cache_alloc+0x136/0x320 mm/slub.c:3867
>   vm_area_alloc+0x1f/0x220 kernel/fork.c:465
>   mmap_region+0x3ae/0x2a90 mm/mmap.c:2804
>   do_mmap+0x890/0xef0 mm/mmap.c:1379
>   vm_mmap_pgoff+0x1a7/0x3c0 mm/util.c:573
>   ksys_mmap_pgoff+0x421/0x5a0 mm/mmap.c:1425
>   __do_sys_mmap arch/x86/kernel/sys_x86_64.c:93 [inline]
>   __se_sys_mmap arch/x86/kernel/sys_x86_64.c:86 [inline]
>   __x64_sys_mmap+0x125/0x190 arch/x86/kernel/sys_x86_64.c:86
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xd0/0x250 arch/x86/entry/common.c:83
>   entry_SYSCALL_64_after_hwframe+0x62/0x6a
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 5059 at include/linux/rmap.h:202 __folio_rmap_sanity_checks+0x4d5/0x630 include/linux/rmap.h:202
> Modules linked in:
> CPU: 1 PID: 5059 Comm: syz-executor115 Not tainted 6.7.0-rc8-next-20240102-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
> RIP: 0010:__folio_rmap_sanity_checks+0x4d5/0x630 include/linux/rmap.h:202
> Code: 41 83 e4 01 44 89 e6 e8 79 bc b7 ff 45 84 e4 0f 85 08 fc ff ff e8 3b c1 b7 ff 48 c7 c6 e0 b5 d9 8a 48 89 df e8 5c 12 f7 ff 90 <0f> 0b 90 e9 eb fb ff ff e8 1e c1 b7 ff be 01 00 00 00 48 89 df e8
> RSP: 0018:ffffc900038df978 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: ffffea00008cde00 RCX: ffffffff81687419
> RDX: ffff88807becbb80 RSI: ffffffff81d06104 RDI: 0000000000000000
> RBP: ffffea00008cde00 R08: 0000000000000000 R09: fffffbfff1e75f6a
> R10: ffffffff8f3afb57 R11: 0000000000000001 R12: 0000000000000000
> R13: 0000000000000001 R14: 0000000000000000 R15: dffffc0000000000
> FS:  0000555556508380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000200000c0 CR3: 0000000079000000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   <TASK>
>   __folio_add_rmap mm/rmap.c:1167 [inline]
>   __folio_add_file_rmap mm/rmap.c:1452 [inline]
>   folio_add_file_rmap_ptes+0x8e/0x2c0 mm/rmap.c:1478
>   insert_page_into_pte_locked.isra.0+0x34d/0x960 mm/memory.c:1874
>   insert_page mm/memory.c:1900 [inline]
>   vm_insert_page+0x62c/0x8c0 mm/memory.c:2053
>   packet_mmap+0x314/0x570 net/packet/af_packet.c:4594
>   call_mmap include/linux/fs.h:2090 [inline]
>   mmap_region+0x745/0x2a90 mm/mmap.c:2819
>   do_mmap+0x890/0xef0 mm/mmap.c:1379
>   vm_mmap_pgoff+0x1a7/0x3c0 mm/util.c:573
>   ksys_mmap_pgoff+0x421/0x5a0 mm/mmap.c:1425
>   __do_sys_mmap arch/x86/kernel/sys_x86_64.c:93 [inline]
>   __se_sys_mmap arch/x86/kernel/sys_x86_64.c:86 [inline]
>   __x64_sys_mmap+0x125/0x190 arch/x86/kernel/sys_x86_64.c:86
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xd0/0x250 arch/x86/entry/common.c:83
>   entry_SYSCALL_64_after_hwframe+0x62/0x6a

If I am not wrong, that triggers:

VM_WARN_ON_FOLIO(folio_test_large(folio) &&
		 !folio_test_large_rmappable(folio), folio);

So we are trying to rmap a large folio that did not go through 
folio_prep_large_rmappable().

net/packet/af_packet.c calls vm_insert_page() on some pages/folios stoed 
in the "struct packet_ring_buffer". No idea where that comes from, but I 
suspect it's simply some compound allocation.

Likely, rmap handling is completely bogus for these folios?

-- 
Cheers,

David / dhildenb