On 12/07, Matthew Wilcox wrote: > On Mon, Dec 06, 2021 at 05:56:31PM -0800, Andrew Morton wrote: > > On Sat, 04 Dec 2021 01:55:17 -0800 syzbot <syzbot+7cd473c2cac13fd2dd72@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > > > > Hello, > > > > > > syzbot found the following issue on: > > > > > > HEAD commit: 58e1100fdc59 MAINTAINERS: co-maintain random.c > > > git tree: upstream > > > console output: https://syzkaller.appspot.com/x/log.txt?x=1362881eb00000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=e9ea28d2c3c2c389 > > > dashboard link: https://syzkaller.appspot.com/bug?extid=7cd473c2cac13fd2dd72 > > > compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.2 > > > > > > 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+7cd473c2cac13fd2dd72@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > > > BUG: kernel NULL pointer dereference, address: 0000000000000000 > > > > cc linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx > > > > And willy, who might help with diagnosing this. But it does seem that > > f2fs got itself a NULL page* then put it in places where it shouldn't have. > > Oh -- it's not a NULL data pointer. It's a NULL instruction pointer. > > > > #PF: supervisor instruction fetch in kernel mode > > > #PF: error_code(0x0010) - not-present page > > > PGD 70764067 P4D 70764067 PUD 0 > > > Oops: 0010 [#1] PREEMPT SMP KASAN > > > CPU: 1 PID: 6541 Comm: syz-executor.3 Not tainted 5.16.0-rc3-syzkaller #0 > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > > RIP: 0010:0x0 > > > Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6. > > > RSP: 0018:ffffc900027ff7f8 EFLAGS: 00010246 > > > RAX: 1ffffffff14fef03 RBX: ffffffff8a7f7818 RCX: ffff88801b40d700 > > > RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffea0002790ec0 > > > RBP: dffffc0000000000 R08: ffffffff81b0fa16 R09: fffff940004f21d9 > > > R10: fffff940004f21d9 R11: 0000000000000000 R12: ffff88806c11c7b0 > > > R13: 0000000000000000 R14: 1ffffd40004f21d9 R15: ffffea0002790ec0 > > > FS: 0000555557165400(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000 > > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > CR2: ffffffffffffffd6 CR3: 0000000030d85000 CR4: 00000000003526e0 > > > Call Trace: > > > <TASK> > > > folio_mark_dirty+0x136/0x270 mm/page-writeback.c:2639 > > if (likely(mapping)) { > ... > if (folio_test_reclaim(folio)) > folio_clear_reclaim(folio); > return mapping->a_ops->set_page_dirty(&folio->page); > > how do we get to a NULL ->set_page_dirty for a metadata page's > mapping->a_ops? This is definitely an f2fs expert question. I can't find anything in f2fs, since that page was got by f2fs_grab_meta_page along with grab_cache_page() that we never unlocked it. 40 struct page *f2fs_grab_meta_page(struct f2fs_sb_info *sbi, pgoff_t index) 41 { 42 struct address_space *mapping = META_MAPPING(sbi); 43 struct page *page; 44 repeat: 45 page = f2fs_grab_cache_page(mapping, index, false); -> grab_cache_page(mapping, index); 46 if (!page) { 47 cond_resched(); 48 goto repeat; 49 } 50 f2fs_wait_on_page_writeback(page, META, true, true); 51 if (!PageUptodate(page)) 52 SetPageUptodate(page); 53 return page; 54 } Suspecting something in folio wrt folio_mapping()? 81 bool set_page_dirty(struct page *page) 82 { 83 return folio_mark_dirty(page_folio(page)); 84 } > > > > f2fs_update_meta_page+0x4b/0x380 fs/f2fs/segment.c:2485 > > > do_checkpoint fs/f2fs/checkpoint.c:1513 [inline] > > > f2fs_write_checkpoint+0x31ad/0x5430 fs/f2fs/checkpoint.c:1674 > > > f2fs_issue_checkpoint+0x361/0x4e0 > > > sync_filesystem+0x19c/0x1f0 fs/sync.c:63 > > > generic_shutdown_super+0x6b/0x300 fs/super.c:448 > > > kill_block_super+0x79/0xd0 fs/super.c:1397 > > > kill_f2fs_super+0x2f9/0x3c0 fs/f2fs/super.c:4478 > > > deactivate_locked_super+0xa7/0xf0 fs/super.c:335 > > > cleanup_mnt+0x462/0x510 fs/namespace.c:1137 > > > task_work_run+0x146/0x1c0 kernel/task_work.c:164 > > > tracehook_notify_resume include/linux/tracehook.h:189 [inline] > > > exit_to_user_mode_loop kernel/entry/common.c:175 [inline] > > > exit_to_user_mode_prepare+0x209/0x220 kernel/entry/common.c:207 > > > __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline] > > > syscall_exit_to_user_mode+0x2e/0x70 kernel/entry/common.c:300 > > > do_syscall_64+0x53/0xd0 arch/x86/entry/common.c:86 > > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > > RIP: 0033:0x7f6cfdd59f57 > > > Code: ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 > > > RSP: 002b:00007fffcbddcad8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6 > > > RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f6cfdd59f57 > > > RDX: 00007fffcbddcbac RSI: 000000000000000a RDI: 00007fffcbddcba0 > > > RBP: 00007fffcbddcba0 R08: 00000000ffffffff R09: 00007fffcbddc970 > > > R10: 0000555557166903 R11: 0000000000000246 R12: 00007f6cfddb2105 > > > R13: 00007fffcbdddc60 R14: 0000555557166810 R15: 00007fffcbdddca0 > > > </TASK> > > > Modules linked in: > > > CR2: 0000000000000000 > > > ---[ end trace 08eda5a5e35b48a0 ]--- > > > RIP: 0010:0x0 > > > Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6. > > > RSP: 0018:ffffc900027ff7f8 EFLAGS: 00010246 > > > RAX: 1ffffffff14fef03 RBX: ffffffff8a7f7818 RCX: ffff88801b40d700 > > > RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffea0002790ec0 > > > RBP: dffffc0000000000 R08: ffffffff81b0fa16 R09: fffff940004f21d9 > > > R10: fffff940004f21d9 R11: 0000000000000000 R12: ffff88806c11c7b0 > > > R13: 0000000000000000 R14: 1ffffd40004f21d9 R15: ffffea0002790ec0 > > > FS: 0000555557165400(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000 > > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > CR2: ffffffffffffffd6 CR3: 0000000030d85000 CR4: 00000000003526e0 > > > > > > > > > --- > > > 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@xxxxxxxxxxxxxxxx. > > > > > > syzbot will keep track of this issue. See: > > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > > _______________________________________________ > Linux-f2fs-devel mailing list > Linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
