Re: [syzbot] [mm?] BUG: Bad page state in corrupted

Re: [syzbot] [mm?] BUG: Bad page state in corrupted

[Andrew Morton]

On Wed, 12 Aug 2026 17:08:33 -0700 syzbot <syzbot+237bbeed8dfe0699b7f5@syzkaller.appspotmail.com> wrote:

> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    ba5cc80fd326 Merge branch 'for-next/core' into for-kernelci
> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=14db42c6580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=ccf4bea59f67007
> dashboard link: https://syzkaller.appspot.com/bug?extid=237bbeed8dfe0699b7f5
> compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
> userspace arch: arm64
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1690bfb9580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17fc0149580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/959ad5f4e730/disk-ba5cc80f.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/0787d25f251e/vmlinux-ba5cc80f.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/2e85c36fabac/Image-ba5cc80f.gz.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+237bbeed8dfe0699b7f5@syzkaller.appspotmail.com
> 
> BUG: Bad page state in process syz-executor210  pfn:112724

(cc's added)

Thanks.  I asked gemini to triage this and it suggested that
bpf_xdp_shrink_data()'s callee is freeing a page directly via
page_frag_free(), whereas it should have used the page_pool APIs.

	https://gemini.google.com/app/5fde6de04c8e128f

> page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff0000d2724480 pfn:0x112724
> flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
> raw: 05ffc00000000000 dead000000000040 ffff0000c30e0000 0000000000000000
> raw: ffff0000d2724480 3fffffffffffffff 00000000ffffffff 0000000000000000
> page dumped because: page_pool leak
> Modules linked in:
> CPU: 1 UID: 0 PID: 4718 Comm: syz-executor210 Not tainted syzkaller #0 PREEMPT 
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
> 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
>  dump_stack+0x1c/0x28 lib/dump_stack.c:129
>  bad_page+0x194/0x1d0 mm/page_alloc.c:643
>  free_page_is_bad mm/page_alloc.c:1078 [inline]
>  __free_pages_prepare mm/page_alloc.c:1397 [inline]
>  __free_frozen_pages+0xb68/0xbb8 mm/page_alloc.c:2950
>  free_frozen_pages+0x14/0x20 mm/page_alloc.c:2988
>  page_frag_free+0x18c/0x1e0 mm/page_frag_cache.c:169
>  __xdp_return+0x200/0x738 net/core/xdp.c:448
>  bpf_xdp_shrink_data+0x288/0x348 net/core/filter.c:4294
>  bpf_xdp_frags_shrink_tail+0x1c0/0x424 net/core/filter.c:4318
>  ____bpf_xdp_adjust_tail net/core/filter.c:4340 [inline]
>  bpf_xdp_adjust_tail+0x198/0x1dc net/core/filter.c:4333
>  bpf_prog_5d7dc57dfd7f985a+0x38/0x58
>  bpf_dispatcher_xdp_func+0x30/0x44 net/core/filter.c:12027
>  __bpf_prog_run include/linux/filter.h:724 [inline]
>  bpf_prog_run_xdp include/net/xdp.h:696 [inline]
>  bpf_prog_run_generic_xdp+0x4a4/0x11e0 net/core/dev.c:5498
>  netif_receive_generic_xdp net/core/dev.c:5614 [inline]
>  do_xdp_generic+0x97c/0x11e0 net/core/dev.c:5676
>  tun_get_user+0x1e24/0x364c drivers/net/tun.c:1874
>  tun_chr_write_iter+0xfc/0x168 drivers/net/tun.c:2001
>  new_sync_write fs/read_write.c:595 [inline]
>  vfs_write+0x51c/0xa0c fs/read_write.c:687
>  ksys_write+0x12c/0x228 fs/read_write.c:739
>  __do_sys_write fs/read_write.c:750 [inline]
>  __se_sys_write fs/read_write.c:747 [inline]
>  __arm64_sys_write+0x84/0x98 fs/read_write.c:747
>  __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
>  invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
>  el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
>  do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
>  el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:738
>  el0t_64_sync_handler+0x48/0x148 arch/arm64/kernel/entry-common.c:757
>  el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:590
> BUG: Bad page state in process syz-executor210  pfn:113883
> page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff0000d3883c00 pfn:0x113883
> flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
> raw: 05ffc00000000000 dead000000000040 ffff0000c30e0000 0000000000000000
> raw: ffff0000d3883c00 0000000000000001 00000000ffffffff 0000000000000000
> page dumped because: page_pool leak
> Modules linked in:
> CPU: 1 UID: 0 PID: 4718 Comm: syz-executor210 Tainted: G    B               syzkaller #0 PREEMPT 
> Tainted: [B]=BAD_PAGE
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
> 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
>  dump_stack+0x1c/0x28 lib/dump_stack.c:129
>  bad_page+0x194/0x1d0 mm/page_alloc.c:643
> 
> 
> ---
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