[syzbot] KASAN: use-after-free Read in sysv_new_block

From: syzbot
Date: Thu Dec 01 2022 - 07:49:53 EST

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Hello,

syzbot found the following issue on:

HEAD commit: 01f856ae6d0c Merge tag 'net-6.1-rc8-2' of git://git.kernel..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=15fddbc5880000
kernel config: https://syzkaller.appspot.com/x/.config?x=2325e409a9a893e1
dashboard link: https://syzkaller.appspot.com/bug?extid=eda782c229b243c648e9
compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=179d6e75880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=124b96a7880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5428d604f56a/disk-01f856ae.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e953d290d254/vmlinux-01f856ae.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3f71610a4904/bzImage-01f856ae.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/e2e13128a6e4/mount_1.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+eda782c229b243c648e9@xxxxxxxxxxxxxxxxxxxxxxxxx

sysv_free_block: flc_count > flc_size
sysv_free_block: flc_count > flc_size
sysv_free_block: flc_count > flc_size
sysv_free_block: flc_count > flc_size
sysv_free_block: flc_count > flc_size
sysv_free_block: flc_count > flc_size
sysv_free_block: flc_count > flc_size
sysv_free_block: flc_count > flc_size
sysv_free_block: flc_count > flc_size
sysv_free_block: flc_count > flc_size
==================================================================
BUG: KASAN: use-after-free in sysv_new_block+0x73f/0x910 fs/sysv/balloc.c:113
Read of size 4 at addr ffff8880712d60c8 by task syz-executor118/3633

CPU: 1 PID: 3633 Comm: syz-executor118 Not tainted 6.1.0-rc7-syzkaller-00101-g01f856ae6d0c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106
print_address_description+0x74/0x340 mm/kasan/report.c:284
print_report+0x107/0x1f0 mm/kasan/report.c:395
kasan_report+0xcd/0x100 mm/kasan/report.c:495
sysv_new_block+0x73f/0x910 fs/sysv/balloc.c:113
alloc_branch fs/sysv/itree.c:134 [inline]
get_block+0x2b5/0x16d0 fs/sysv/itree.c:251
__block_write_begin_int+0x54c/0x1a80 fs/buffer.c:1991
__block_write_begin fs/buffer.c:2041 [inline]
block_write_begin+0x93/0x1e0 fs/buffer.c:2102
sysv_write_begin+0x2d/0x60 fs/sysv/itree.c:485
generic_perform_write+0x2e4/0x5e0 mm/filemap.c:3753
__generic_file_write_iter+0x176/0x400 mm/filemap.c:3881
generic_file_write_iter+0xab/0x310 mm/filemap.c:3913
call_write_iter include/linux/fs.h:2199 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x7dc/0xc50 fs/read_write.c:584
ksys_write+0x177/0x2a0 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f3801c82ee9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 91 18 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:00007ffce2453d28 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f3801c82ee9
RDX: 00000000fffffd5e RSI: 000000002000ad00 RDI: 0000000000000004
RBP: 00007ffce2453e20 R08: 0000000000000031 R09: 0000000000000031
R10: 0000000000009e07 R11: 0000000000000246 R12: 0000000000000048
R13: 00007f3801d0c7e0 R14: 00007ffce2453d82 R15: 00007ffce2453df0
</TASK>

The buggy address belongs to the physical page:
page:ffffea0001c4b580 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x712d6
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0001c4b5c8 ffffea0001c4b548 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 0x8(__GFP_MOVABLE), pid 1, tgid 1 (swapper/0), ts 10227233924, free_ts 11569433830
split_map_pages+0x25b/0x540 mm/compaction.c:97
isolate_freepages_range+0x4ac/0x510 mm/compaction.c:735
alloc_contig_range+0x6a9/0x980 mm/page_alloc.c:9374
__alloc_contig_pages mm/page_alloc.c:9397 [inline]
alloc_contig_pages+0x3c8/0x4e0 mm/page_alloc.c:9474
debug_vm_pgtable_alloc_huge_page+0xcd/0x11e mm/debug_vm_pgtable.c:1098
init_args+0xa3a/0xdba mm/debug_vm_pgtable.c:1221
debug_vm_pgtable+0x9a/0x4a6 mm/debug_vm_pgtable.c:1259
do_one_initcall+0x1c9/0x400 init/main.c:1303
do_initcall_level+0x168/0x218 init/main.c:1376
do_initcalls+0x4b/0x8c init/main.c:1392
kernel_init_freeable+0x428/0x5d5 init/main.c:1631
kernel_init+0x19/0x2b0 init/main.c:1519
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1459 [inline]
free_pcp_prepare+0x80c/0x8f0 mm/page_alloc.c:1509
free_unref_page_prepare mm/page_alloc.c:3387 [inline]
free_unref_page+0x7d/0x5f0 mm/page_alloc.c:3483
free_contig_range+0xa3/0x160 mm/page_alloc.c:9496
destroy_args+0xfe/0x935 mm/debug_vm_pgtable.c:1031
debug_vm_pgtable+0x44d/0x4a6 mm/debug_vm_pgtable.c:1354
do_one_initcall+0x1c9/0x400 init/main.c:1303
do_initcall_level+0x168/0x218 init/main.c:1376
do_initcalls+0x4b/0x8c init/main.c:1392
kernel_init_freeable+0x428/0x5d5 init/main.c:1631
kernel_init+0x19/0x2b0 init/main.c:1519
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

Memory state around the buggy address:
ffff8880712d5f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff8880712d6000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8880712d6080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff8880712d6100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff8880712d6180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

---
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