[syzbot] [ext4?] BUG: unable to handle kernel paging request in do_split

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 55027e689933 Merge tag 'input-for-v6.10-rc5' of git://git...
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=100ec271980000
kernel config: https://syzkaller.appspot.com/x/.config?x=67463c0717b8d4ca
dashboard link: https://syzkaller.appspot.com/bug?extid=ae688d469e36fb5138d0
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=14296bb6980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10a53e3e980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5a4561e75890/disk-55027e68.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/40e478722974/vmlinux-55027e68.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d3bbbd2462f2/bzImage-55027e68.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/451986899a3c/mount_0.gz

Bisection is inconclusive: the first bad commit could be any of:

3b51788a2d5f IB/hfi1: use new function dev_fetch_sw_netstats
44fa32f008ab net: add function dev_fetch_sw_netstats for fetching pcpu_sw_netstats
3618ad2a7c0e virtio-net: ethtool configurable RXCSUM
9d0151673e70 net: macsec: use new function dev_fetch_sw_netstats
c9bf52a173c7 net/af_unix: Remove unused old_pid variable
ec173778e96e net: usb: qmi_wwan: use new function dev_fetch_sw_netstats
0403a2b53c29 net/tls: use semicolons rather than commas to separate statements
ab2b3ff21b9f net: usbnet: use new function dev_fetch_sw_netstats
1f68b2096f65 qtnfmac: use new function dev_fetch_sw_netstats
6159e9633f17 net/ipv6: use semicolons rather than commas to separate statements
44797589c20e tcp: use semicolons rather than commas to separate statements
f3f04f0f3ab9 net: bridge: use new function dev_fetch_sw_netstats
7e38b03f0fe7 net: mscc: ocelot: remove duplicate ocelot_port_dev_check
a0d269810185 net: dsa: use new function dev_fetch_sw_netstats
c93c5482c7d4 Merge branch 'macb-support-the-2-deep-Tx-queue-on-at91'
cf89f18fa407 iptunnel: use new function dev_fetch_sw_netstats
0a4e9ce17ba7 macb: support the two tx descriptors on at91rm9200
6401297e7610 mac80211: use new function dev_fetch_sw_netstats
3569939a811e net: openvswitch: use new function dev_fetch_sw_netstats
73d742281383 macb: prepare at91 to use a 2-frame TX queue
5fc3594d36d1 xfrm: use new function dev_fetch_sw_netstats
fa6031df12fc macb: add RM9200's interrupt flag TBRE
a003ec1f47bc Merge branch 'net-add-and-use-function-dev_fetch_sw_netstats-for-fetching-pcpu_sw_netstats'
ccdf7fae3afa Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next
30cf856a691f i40e: Allow changing FEC settings on X722 if supported by FW
a308283fdbf7 Merge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf-next
793d5d612426 netfilter: flowtable: reduce calls to pskb_may_pull()
f2bf814a27c5 e1000: remove unused and incorrect code
d3519cb89f6d netfilter: nf_tables: add inet ingress support
d5e6f064ac66 Merge branch '40GbE-Intel-Wired-LAN-Driver-Updates-2020-10-12'
50172733d01c Merge tag 'mlx5-updates-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/saeed/linux
60a3815da702 netfilter: add inet ingress support
d25e2e9388ed netfilter: restore NF_INET_NUMHOOKS

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14154fda980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ae688d...@syzkaller.appspotmail.com

EXT4-fs error (device loop0): ext4_orphan_get:1399: comm syz-executor306: couldn't read orphan inode 15 (err -117)
EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
BUG: unable to handle page fault for address: ffffed11022e24fe
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 23ffee067 P4D 23ffee067 PUD 0
Oops: Oops: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 0 PID: 5079 Comm: syz-executor306 Not tainted 6.10.0-rc5-syzkaller-00018-g55027e689933 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
RIP: 0010:do_split+0x150b/0x2490 fs/ext4/namei.c:2046
Code: 89 f8 48 c1 e8 03 0f b6 04 10 84 c0 48 89 74 24 18 0f 85 f5 0c 00 00 46 8b 3c f6 41 8d 46 ff 48 8d 1c c6 48 89 d8 48 c1 e8 03 <0f> b6 04 10 84 c0 4c 8b a4 24 98 00 00 00 0f 85 f7 0c 00 00 8b 1b
RSP: 0018:ffffc9000327f060 EFLAGS: 00010a02
RAX: 1ffff111022e24fe RBX: ffff8888117127f0 RCX: ffff8880237e1e00
RDX: dffffc0000000000 RSI: ffff8880117127f8 RDI: ffff8880117127f8
RBP: ffffc9000327f250 R08: ffffffff825fc2ad R09: ffffffff82541cf8
R10: 0000000000000007 R11: ffffffff825435f0 R12: 0000000000000000
R13: 0000000000000400 R14: 0000000000000000 R15: 000000002b74e18c
FS: 00005555787b4380(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffed11022e24fe CR3: 0000000043598000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
make_indexed_dir+0xdaf/0x13c0 fs/ext4/namei.c:2341
ext4_add_entry+0x222a/0x25d0 fs/ext4/namei.c:2451
ext4_rename fs/ext4/namei.c:3936 [inline]
ext4_rename2+0x26e5/0x4370 fs/ext4/namei.c:4214
vfs_rename+0xbdb/0xf00 fs/namei.c:4887
do_renameat2+0xd94/0x13f0 fs/namei.c:5044
__do_sys_rename fs/namei.c:5091 [inline]
__se_sys_rename fs/namei.c:5089 [inline]
__x64_sys_rename+0x86/0xa0 fs/namei.c:5089
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe5c7dcdb59
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 17 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:00007ffcd201c228 EFLAGS: 00000246 ORIG_RAX: 0000000000000052
RAX: ffffffffffffffda RBX: 00007fe5c7e16568 RCX: 00007fe5c7dcdb59
RDX: 0000000000000000 RSI: 0000000020000f40 RDI: 00000000200003c0
RBP: 00007fe5c7e16668 R08: 00005555787b54c0 R09: 00005555787b54c0
R10: 00005555787b54c0 R11: 0000000000000246 R12: 00007ffcd201c250
R13: 00007ffcd201c478 R14: 431bde82d7b634db R15: 00007fe5c7e1603b
</TASK>
Modules linked in:
CR2: ffffed11022e24fe
---[ end trace 0000000000000000 ]---
RIP: 0010:do_split+0x150b/0x2490 fs/ext4/namei.c:2046
Code: 89 f8 48 c1 e8 03 0f b6 04 10 84 c0 48 89 74 24 18 0f 85 f5 0c 00 00 46 8b 3c f6 41 8d 46 ff 48 8d 1c c6 48 89 d8 48 c1 e8 03 <0f> b6 04 10 84 c0 4c 8b a4 24 98 00 00 00 0f 85 f7 0c 00 00 8b 1b
RSP: 0018:ffffc9000327f060 EFLAGS: 00010a02
RAX: 1ffff111022e24fe RBX: ffff8888117127f0 RCX: ffff8880237e1e00
RDX: dffffc0000000000 RSI: ffff8880117127f8 RDI: ffff8880117127f8
RBP: ffffc9000327f250 R08: ffffffff825fc2ad R09: ffffffff82541cf8
R10: 0000000000000007 R11: ffffffff825435f0 R12: 0000000000000000
R13: 0000000000000400 R14: 0000000000000000 R15: 000000002b74e18c
FS: 00005555787b4380(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffed11022e24fe CR3: 0000000043598000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 89 f8 mov %edi,%eax
2: 48 c1 e8 03 shr $0x3,%rax
6: 0f b6 04 10 movzbl (%rax,%rdx,1),%eax
a: 84 c0 test %al,%al
c: 48 89 74 24 18 mov %rsi,0x18(%rsp)
11: 0f 85 f5 0c 00 00 jne 0xd0c
17: 46 8b 3c f6 mov (%rsi,%r14,8),%r15d
1b: 41 8d 46 ff lea -0x1(%r14),%eax
1f: 48 8d 1c c6 lea (%rsi,%rax,8),%rbx
23: 48 89 d8 mov %rbx,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 0f b6 04 10 movzbl (%rax,%rdx,1),%eax <-- trapping instruction
2e: 84 c0 test %al,%al
30: 4c 8b a4 24 98 00 00 mov 0x98(%rsp),%r12
37: 00
38: 0f 85 f7 0c 00 00 jne 0xd35
3e: 8b 1b mov (%rbx),%ebx


---
This report is generated by a bot. It may contain errors.
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

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If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[Edward Adam Davis]

if split is too small, such as 0, use it to calculate continued will out of bound map

#syz test: upstream 55027e689933

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index a630b27a4cc6..0a111274dc4a 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2043,7 +2043,7 @@ static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir,
split = count/2;

hash2 = map[split].hash;
- continued = hash2 == map[split - 1].hash;
+ continued = split > 0 ? hash2 == map[split - 1].hash : 0;
dxtrace(printk(KERN_INFO "Split block %lu at %x, %i/%i\n",
(unsigned long)dx_get_block(frame->at),
hash2, split, count-split));

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+ae688d...@syzkaller.appspotmail.com

Tested on:

commit: 55027e68 Merge tag 'input-for-v6.10-rc5' of git://git...
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=16bb8761980000

kernel config: https://syzkaller.appspot.com/x/.config?x=67463c0717b8d4ca
dashboard link: https://syzkaller.appspot.com/bug?extid=ae688d469e36fb5138d0
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=10754c81980000

Note: testing is done by a robot and is best-effort only.