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Date: Tue, 14 May 2024 07:09:42 -0700
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Subject: [syzbot] [ext4?] KASAN: use-after-free Read in __ext4_check_dir_entry (2)
From: syzbot <syzbot+11af34d3c0711f233fd4@syzkaller.appspotmail.com>
To: adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, 
	linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, tytso@mit.edu
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Hello,

syzbot found the following issue on:

HEAD commit:    448b3fe5a0ea Merge tag 'hwmon-for-v6.9-rc8' of git://git.k..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1797c7a8980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9d7ea7de0cb32587
dashboard link: https://syzkaller.appspot.com/bug?extid=11af34d3c0711f233fd4
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=105badd4980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16f14fa8980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ccbdd58c1f3e/disk-448b3fe5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6786079c3170/vmlinux-448b3fe5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/496bdcf3d703/bzImage-448b3fe5.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/b2986628c43b/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+11af34d3c0711f233fd4@syzkaller.appspotmail.com

EXT4-fs error (device loop0): make_indexed_dir:2282: inode #2: block 255: comm syz-executor396: bad entry in directory: rec_len is smaller than minimal - offset=0, inode=5120, rec_len=0, size=993 fake=0
EXT4-fs warning (device loop0): dx_probe:832: inode #2: comm syz-executor396: Unrecognised inode hash code 49
EXT4-fs warning (device loop0): dx_probe:965: inode #2: comm syz-executor396: Corrupt directory, running e2fsck is recommended
==================================================================
BUG: KASAN: use-after-free in __ext4_check_dir_entry+0x6fd/0x880 fs/ext4/dir.c:85
Read of size 2 at addr ffff8880683ae003 by task syz-executor396/5071

CPU: 0 PID: 5071 Comm: syz-executor396 Not tainted 6.9.0-rc7-syzkaller-00117-g448b3fe5a0ea #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 __ext4_check_dir_entry+0x6fd/0x880 fs/ext4/dir.c:85
 ext4_readdir+0x145d/0x3800 fs/ext4/dir.c:258
 iterate_dir+0x539/0x6f0 fs/readdir.c:110
 __do_sys_getdents64 fs/readdir.c:409 [inline]
 __se_sys_getdents64+0x20d/0x4f0 fs/readdir.c:394
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8311a13ed9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd43d6adc8 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007ffd43d6ae10 RCX: 00007f8311a13ed9
RDX: 0000000000000010 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007ffd43d6ae18 R08: 000055556bcad0c0 R09: 000055556bcad0c0
R10: 000055556bcad0c0 R11: 0000000000000246 R12: 00007f8311a906a0
R13: 00007ffd43d6ae10 R14: 0000000000000004 R15: 0000000000000003
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x683ae
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000000 ffffea0001a0ebc8 ffff8880b9444570 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO), pid 5065, tgid -1706810074 (sftp-server), ts 5065, free_ts 54138803695
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1ea/0x210 mm/page_alloc.c:1534
 prep_new_page mm/page_alloc.c:1541 [inline]
 get_page_from_freelist+0x3410/0x35b0 mm/page_alloc.c:3317
 __alloc_pages+0x256/0x6c0 mm/page_alloc.c:4575
 alloc_pages_mpol+0x3e8/0x680 mm/mempolicy.c:2264
 vma_alloc_folio+0xf3/0x1f0 mm/mempolicy.c:2303
 folio_prealloc+0x31/0x170
 alloc_anon_folio mm/memory.c:4375 [inline]
 do_anonymous_page mm/memory.c:4433 [inline]
 do_pte_missing mm/memory.c:3878 [inline]
 handle_pte_fault mm/memory.c:5300 [inline]
 __handle_mm_fault+0x3a03/0x7250 mm/memory.c:5441
 handle_mm_fault+0x27f/0x770 mm/memory.c:5606
 do_user_addr_fault arch/x86/mm/fault.c:1331 [inline]
 handle_page_fault arch/x86/mm/fault.c:1474 [inline]
 exc_page_fault+0x446/0x8a0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
page last free pid 5065 tgid 5065 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1141 [inline]
 free_unref_page_prepare+0x97b/0xaa0 mm/page_alloc.c:2347
 free_unref_folios+0x1f2/0xc10 mm/page_alloc.c:2536
 folios_put_refs+0x93a/0xa60 mm/swap.c:1034
 free_pages_and_swap_cache+0x2ea/0x690 mm/swap_state.c:329
 __tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
 tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:366 [inline]
 tlb_flush_mmu+0x3a3/0x680 mm/mmu_gather.c:373
 tlb_finish_mmu+0xd4/0x200 mm/mmu_gather.c:465
 exit_mmap+0x4bb/0xd60 mm/mmap.c:3280
 __mmput+0x115/0x3c0 kernel/fork.c:1346
 exit_mm+0x220/0x310 kernel/exit.c:569
 do_exit+0x99e/0x27e0 kernel/exit.c:865
 do_group_exit+0x207/0x2c0 kernel/exit.c:1027
 __do_sys_exit_group kernel/exit.c:1038 [inline]
 __se_sys_exit_group kernel/exit.c:1036 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1036
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff8880683adf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880683adf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880683ae000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff8880683ae080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880683ae100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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