Re: [f2fs-dev] [syzbot] BUG: unable to handle kernel NULL pointer dereference in set_page_dirty

Re: [f2fs-dev] [syzbot] BUG: unable to handle kernel NULL pointer dereference in set_page_dirty

[Andrew Morton]

(cc fsf2 developers)

On Thu, 25 Aug 2022 08:29:32 -0700 syzbot <syzbot+775a3440817f74fddb8c@syzkaller.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@syzkaller.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
>  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@googlegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.


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Re: [f2fs-dev] [syzbot] BUG: unable to handle kernel NULL pointer dereference in set_page_dirty

[Jaegeuk Kim]

On 08/25, Andrew Morton wrote:
> (cc fsf2 developers)
> 
> On Thu, 25 Aug 2022 08:29:32 -0700 syzbot <syzbot+775a3440817f74fddb8c@syzkaller.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@syzkaller.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@googlegroups.com.
> > 
> > syzbot will keep track of this issue. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.


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Re: [f2fs-dev] [syzbot] BUG: unable to handle kernel NULL pointer dereference in set_page_dirty

[Matthew Wilcox]

On Mon, Aug 29, 2022 at 10:52:57AM -0700, Jaegeuk Kim wrote:
> On 08/25, Andrew Morton wrote:
> > (cc fsf2 developers)
> > 
> > On Thu, 25 Aug 2022 08:29:32 -0700 syzbot <syzbot+775a3440817f74fddb8c@syzkaller.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@syzkaller.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?

Not directly, but there was a related change, 0af573780b0b which
requires aops->set_page_dirty to be set; is that perhaps missing?
I don't see one in the f2fs_compress_aops, for example.

The other possibiity is that it's a mapping that is missing an ->a_ops.
Is that something f2fs ever does?

I only managed to narrow down the crash to the line:
                return mapping->a_ops->dirty_folio(mapping, folio);
so either mapping->a_ops is NULL or mapping->a_ops->dirty_folio is
NULL.  The reproducer was on ARM and ARM doesn't emit a 'Code:' line,
unlike x86.


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Re: [f2fs-dev] [syzbot] BUG: unable to handle kernel NULL pointer dereference in set_page_dirty

[Jaegeuk Kim]

On 08/29, Matthew Wilcox wrote:
> On Mon, Aug 29, 2022 at 10:52:57AM -0700, Jaegeuk Kim wrote:
> > On 08/25, Andrew Morton wrote:
> > > (cc fsf2 developers)
> > > 
> > > On Thu, 25 Aug 2022 08:29:32 -0700 syzbot <syzbot+775a3440817f74fddb8c@syzkaller.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@syzkaller.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?
> 
> Not directly, but there was a related change, 0af573780b0b which
> requires aops->set_page_dirty to be set; is that perhaps missing?
> I don't see one in the f2fs_compress_aops, for example.

Do you mean dirty_folio? I think all aops have it except the compressed one
that we don't make it dirty.

> 
> The other possibiity is that it's a mapping that is missing an ->a_ops.
> Is that something f2fs ever does?

Hmm, no, I haven't seen this before, and we set aops when mounting the
file system. Ah, if this happens on the corrupted image, yeah, maybe.. I need
to check the error path in f2fs_fill_super.

> 
> I only managed to narrow down the crash to the line:
>                 return mapping->a_ops->dirty_folio(mapping, folio);
> so either mapping->a_ops is NULL or mapping->a_ops->dirty_folio is
> NULL.  The reproducer was on ARM and ARM doesn't emit a 'Code:' line,
> unlike x86.


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Re: [f2fs-dev] [syzbot] BUG: unable to handle kernel NULL pointer dereference in set_page_dirty

[Jaegeuk Kim]

On 08/29, Jaegeuk Kim wrote:
> On 08/29, Matthew Wilcox wrote:
> > On Mon, Aug 29, 2022 at 10:52:57AM -0700, Jaegeuk Kim wrote:
> > > On 08/25, Andrew Morton wrote:
> > > > (cc fsf2 developers)
> > > > 
> > > > On Thu, 25 Aug 2022 08:29:32 -0700 syzbot <syzbot+775a3440817f74fddb8c@syzkaller.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@syzkaller.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?
> > 
> > Not directly, but there was a related change, 0af573780b0b which
> > requires aops->set_page_dirty to be set; is that perhaps missing?
> > I don't see one in the f2fs_compress_aops, for example.
> 
> Do you mean dirty_folio? I think all aops have it except the compressed one
> that we don't make it dirty.
> 
> > 
> > The other possibiity is that it's a mapping that is missing an ->a_ops.
> > Is that something f2fs ever does?
> 
> Hmm, no, I haven't seen this before, and we set aops when mounting the
> file system. Ah, if this happens on the corrupted image, yeah, maybe.. I need
> to check the error path in f2fs_fill_super.

Fixed by https://lore.kernel.org/linux-f2fs-devel/20220829215206.3082124-1-jaegeuk@kernel.org/T/#u

> 
> > 
> > I only managed to narrow down the crash to the line:
> >                 return mapping->a_ops->dirty_folio(mapping, folio);
> > so either mapping->a_ops is NULL or mapping->a_ops->dirty_folio is
> > NULL.  The reproducer was on ARM and ARM doesn't emit a 'Code:' line,
> > unlike x86.


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Re: [f2fs-dev] [syzbot] BUG: unable to handle kernel NULL pointer dereference in set_page_dirty

[syzbot]

syzbot has found a reproducer for 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=104eb875080000
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
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15aebce7080000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=167b5e33080000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+775a3440817f74fddb8c@syzkaller.appspotmail.com

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
Mem abort info:
  ESR = 0x0000000086000004
  EC = 0x21: IABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x04: level 0 translation fault
user pgtable: 4k pages, 48-bit VAs, pgdp=0000000109ee4000
[0000000000000000] pgd=0000000000000000, p4d=0000000000000000
Internal error: Oops: 86000004 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 3045 Comm: syz-executor330 Not tainted 6.0.0-rc2-syzkaller-16455-ga41a877bc12d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : 0x0
lr : folio_mark_dirty+0xbc/0x208 mm/page-writeback.c:2748
sp : ffff800012783970
x29: ffff800012783970 x28: 0000000000000000 x27: ffff800012783b08
x26: 0000000000000001 x25: 0000000000000400 x24: 0000000000000001
x23: ffff0000c736e000 x22: 0000000000000045 x21: 05ffc00000000015
x20: ffff0000ca7403b8 x19: fffffc00032ec600 x18: 0000000000000181
x17: ffff80000c04d6bc x16: ffff80000dbb8658 x15: 0000000000000000
x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
x11: ff808000083e9814 x10: 0000000000000000 x9 : ffff8000083e9814
x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
x5 : ffff0000cbb19000 x4 : ffff0000cb3d2000 x3 : ffff0000cbb18f80
x2 : fffffffffffffff0 x1 : fffffc00032ec600 x0 : ffff0000ca7403b8
Call trace:
 0x0
 set_page_dirty+0x38/0xbc mm/folio-compat.c:62
 f2fs_update_meta_page+0x80/0xa8 fs/f2fs/segment.c:2369
 do_checkpoint+0x794/0xea8 fs/f2fs/checkpoint.c:1522
 f2fs_write_checkpoint+0x3b8/0x568 fs/f2fs/checkpoint.c:1679
 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 ]---



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