CVE-2023-52603

In the Linux kernel, the following vulnerability has been resolved:

UBSAN: array-index-out-of-bounds in dtSplitRoot

Syzkaller reported the following issue:

oop0: detected capacity change from 0 to 32768

UBSAN: array-index-out-of-bounds in fs/jfs/jfs_dtree.c:1971:9

index -2 is out of range for type 'struct dtslot [128]'

CPU: 0 PID: 3613 Comm: syz-executor270 Not tainted 6.0.0-syzkaller-09423-g493ffd6605b2 #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022

Call Trace:

<TASK>

__dump_stack lib/dump_stack.c:88 [inline]

dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106

ubsan_epilogue lib/ubsan.c:151 [inline]

__ubsan_handle_out_of_bounds+0xdb/0x130 lib/ubsan.c:283

dtSplitRoot+0x8d8/0x1900 fs/jfs/jfs_dtree.c:1971

dtSplitUp fs/jfs/jfs_dtree.c:985 [inline]

dtInsert+0x1189/0x6b80 fs/jfs/jfs_dtree.c:863

jfs_mkdir+0x757/0xb00 fs/jfs/namei.c:270

vfs_mkdir+0x3b3/0x590 fs/namei.c:4013

do_mkdirat+0x279/0x550 fs/namei.c:4038

__do_sys_mkdirat fs/namei.c:4053 [inline]

__se_sys_mkdirat fs/namei.c:4051 [inline]

__x64_sys_mkdirat+0x85/0x90 fs/namei.c:4051

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: 0033:0x7fcdc0113fd9

Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 c0 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007ffeb8bc67d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000102

RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fcdc0113fd9

RDX: 0000000000000000 RSI: 0000000020000340 RDI: 0000000000000003

RBP: 00007fcdc00d37a0 R08: 0000000000000000 R09: 00007fcdc00d37a0

R10: 00005555559a72c0 R11: 0000000000000246 R12: 00000000f8008000

R13: 0000000000000000 R14: 00083878000000f8 R15: 0000000000000000

</TASK>

The issue is caused when the value of fsi becomes less than -1.

The check to break the loop when fsi value becomes -1 is present

but syzbot was able to produce value less than -1 which cause the error.

This patch simply add the change for the values less than 0.

The patch is tested via syzbot.