title: UBSAN: array-index-out-of-bounds in dtSplitRoot
description: 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.
affected:
{
product: Linux
vendor: Linux
defaultStatus: unaffected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions:
version: 1da177e4c3f4, lessThan: e30b52a2ea3d, status: affected, versionType: git
version: 1da177e4c3f4, lessThan: fd3486a89377, status: affected, versionType: git
version: 1da177e4c3f4, lessThan: 7aa33854477d, status: affected, versionType: git
version: 1da177e4c3f4, lessThan: e4ce01c25ccb, status: affected, versionType: git
version: 1da177e4c3f4, lessThan: e4cbc857d75d, status: affected, versionType: git
version: 1da177e4c3f4, lessThan: edff092a5926, status: affected, versionType: git
version: 1da177e4c3f4, lessThan: 6e2902ecc77e, status: affected, versionType: git
version: 1da177e4c3f4, lessThan: 27e56f59bab5, status: affected, versionType: git
}
{
product: Linux
vendor: Linux
defaultStatus: affected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions:
version: 4.19.307, lessThanOrEqual: 4.19.*, status: unaffected, versionType: custom
version: 5.4.269, lessThanOrEqual: 5.4.*, status: unaffected, versionType: custom
version: 5.10.210, lessThanOrEqual: 5.10.*, status: unaffected, versionType: custom
version: 5.15.149, lessThanOrEqual: 5.15.*, status: unaffected, versionType: custom
version: 6.1.77, lessThanOrEqual: 6.1.*, status: unaffected, versionType: custom
version: 6.6.16, lessThanOrEqual: 6.6.*, status: unaffected, versionType: custom
version: 6.7.4, lessThanOrEqual: 6.7.*, status: unaffected, versionType: custom
version: 6.8, lessThanOrEqual: *, status: unaffected, versionType: original_commit_for_fix
}
