linux-kernel - Re: [syzbot] BUG: unable to handle kernel NULL pointer dereference in set_page

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Message-ID: <Ywz8+WUhypEiUfvk@google.com>
Date:   Mon, 29 Aug 2022 10:52:57 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     syzbot <syzbot+775a3440817f74fddb8c@...kaller.appspotmail.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, syzkaller-bugs@...glegroups.com,
        willy@...radead.org, Chao Yu <chao@...nel.org>,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [syzbot] BUG: unable to handle kernel NULL pointer dereference
 in set_page_dirty

On 08/25, Andrew Morton wrote:
> (cc fsf2 developers)
> 
> On Thu, 25 Aug 2022 08:29:32 -0700 syzbot <syzbot+775a3440817f74fddb8c@...kaller.appspotmail.com> wrote:
> 
> > Hello,
> > 
> > syzbot found the following issue on:
> > 
> > HEAD commit:    a41a877bc12d Merge branch 'for-next/fixes' 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=175def47080000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=5cea15779c42821c
> > dashboard link: https://syzkaller.appspot.com/bug?extid=775a3440817f74fddb8c
> > compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
> > userspace arch: arm64
> > 
> > Unfortunately, I don't have any reproducer for this issue yet.
> > 
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+775a3440817f74fddb8c@...kaller.appspotmail.com
> > 
> > Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
> > Mem abort info:
> >   ESR = 0x0000000086000005
> >   EC = 0x21: IABT (current EL), IL = 32 bits
> >   SET = 0, FnV = 0
> >   EA = 0, S1PTW = 0
> >   FSC = 0x05: level 1 translation fault
> > user pgtable: 4k pages, 48-bit VAs, pgdp=00000001249cc000
> > [0000000000000000] pgd=080000012ee65003, p4d=080000012ee65003, pud=0000000000000000
> > Internal error: Oops: 86000005 [#1] PREEMPT SMP
> > Modules linked in:
> > CPU: 0 PID: 3044 Comm: syz-executor.0 Not tainted 6.0.0-rc2-syzkaller-16455-ga41a877bc12d #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/20/2022
> > pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> > pc : 0x0
> > lr : folio_mark_dirty+0xbc/0x208 mm/page-writeback.c:2748
> > sp : ffff800012803830
> > x29: ffff800012803830 x28: ffff0000d02c8000 x27: 0000000000000009
> > x26: 0000000000000001 x25: 0000000000000a00 x24: 0000000000000080
> > x23: 0000000000000000 x22: ffff0000ef276c00 x21: 05ffc00000000007
> > x20: ffff0000f14b83b8 x19: fffffc00036409c0 x18: fffffffffffffff5
> > x17: ffff80000dd7a698 x16: ffff80000dbb8658 x15: 0000000000000000
> > x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
> > x11: ff808000083e9814 x10: 0000000000000000 x9 : ffff8000083e9814
> > x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
> > x5 : ffff0000d9028000 x4 : ffff0000d5c31000 x3 : ffff0000d9027f80
> > x2 : fffffffffffffff0 x1 : fffffc00036409c0 x0 : ffff0000f14b83b8
> > Call trace:
> >  0x0
> >  set_page_dirty+0x38/0xbc mm/folio-compat.c:62

2363 void f2fs_update_meta_page(struct f2fs_sb_info *sbi,
2364                                         void *src, block_t blk_addr)
2365 {       
2366         struct page *page = f2fs_grab_meta_page(sbi, blk_addr);

--> f2fs_grab_meta_page() gives a locked page by grab_cache_page().

2367                                                         
2368         memcpy(page_address(page), src, PAGE_SIZE);
2369         set_page_dirty(page);
2370         f2fs_put_page(page, 1);
2371 } 

Is there a change in folio?

> >  get_next_nat_page+0x198/0x300 fs/f2fs/node.c:154
> >  __flush_nat_entry_set fs/f2fs/node.c:3005 [inline]
> >  f2fs_flush_nat_entries+0x354/0x988 fs/f2fs/node.c:3109
> >  f2fs_write_checkpoint+0x350/0x568 fs/f2fs/checkpoint.c:1667
> >  f2fs_issue_checkpoint+0x1b0/0x234
> >  f2fs_sync_fs+0x8c/0xc8 fs/f2fs/super.c:1651
> >  sync_filesystem+0xe0/0x134 fs/sync.c:66
> >  generic_shutdown_super+0x38/0x190 fs/super.c:474
> >  kill_block_super+0x30/0x78 fs/super.c:1427
> >  kill_f2fs_super+0x140/0x184 fs/f2fs/super.c:4544
> >  deactivate_locked_super+0x70/0xd4 fs/super.c:332
> >  deactivate_super+0xb8/0xbc fs/super.c:363
> >  cleanup_mnt+0x1f8/0x234 fs/namespace.c:1186
> >  __cleanup_mnt+0x20/0x30 fs/namespace.c:1193
> >  task_work_run+0xc4/0x208 kernel/task_work.c:177
> >  resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
> >  do_notify_resume+0x174/0x1d0 arch/arm64/kernel/signal.c:1127
> >  prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
> >  exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
> >  el0_svc+0x9c/0x150 arch/arm64/kernel/entry-common.c:625
> >  el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:642
> >  el0t_64_sync+0x18c/0x190
> > Code: bad PC value
> > ---[ end trace 0000000000000000 ]---
> > 
> > 
> > ---
> > This report is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at syzkaller@...glegroups.com.
> > 
> > syzbot will keep track of this issue. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.