jfs: add dtroot integrity check to prevent index out-of-bounds

Add check_dtroot() to validate dtroot_t integrity, focusing on preventing
index/pointer overflows from on-disk corruption.

Key checks:
 - freecnt bounded by [0, DTROOTMAXSLOT-1] (slot[0] reserved for header).
 - freelist validity: -1 when freecnt=0; 1~DTROOTMAXSLOT-1 when non-zero,
   with linked list checks (no duplicates, proper termination via next=-1).
 - stbl bounds: nextindex within stbl array size; entries within 0~8, no
   duplicates (excluding idx=0).

Invoked in copy_from_dinode() when loading directory inodes, catching
corruption early before directory operations trigger out-of-bounds access.

This fixes the following UBSAN warning.

[  101.832754][ T5960] ------------[ cut here ]------------
[  101.832762][ T5960] UBSAN: array-index-out-of-bounds in fs/jfs/jfs_dtree.c:3713:8
[  101.832792][ T5960] index -1 is out of range for type 'struct dtslot[128]'
[  101.832807][ T5960] CPU: 2 UID: 0 PID: 5960 Comm: 5f7f0caf9979e9d Tainted: G            E       6.18.0-rc4-00250-g2603eb907f03 #119 PREEMPT_{RT,(full
[  101.832817][ T5960] Tainted: [E]=UNSIGNED_MODULE
[  101.832819][ T5960] Hardware name: QEMU Ubuntu 25.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[  101.832823][ T5960] Call Trace:
[  101.832833][ T5960]  <TASK>
[  101.832838][ T5960]  dump_stack_lvl+0x189/0x250
[  101.832909][ T5960]  ? __pfx_dump_stack_lvl+0x10/0x10
[  101.832925][ T5960]  ? __pfx__printk+0x10/0x10
[  101.832934][ T5960]  ? rt_mutex_slowunlock+0x493/0x8a0
[  101.832959][ T5960]  ubsan_epilogue+0xa/0x40
[  101.832966][ T5960]  __ubsan_handle_out_of_bounds+0xe9/0xf0
[  101.833007][ T5960]  dtInsertEntry+0x936/0x1430 [jfs]
[  101.833094][ T5960]  dtSplitPage+0x2c8b/0x3ed0 [jfs]
[  101.833177][ T5960]  ? __pfx_rt_mutex_slowunlock+0x10/0x10
[  101.833193][ T5960]  dtInsert+0x109b/0x6000 [jfs]
[  101.833283][ T5960]  ? rt_mutex_slowunlock+0x493/0x8a0
[  101.833296][ T5960]  ? __pfx_rt_mutex_slowunlock+0x10/0x10
[  101.833307][ T5960]  ? rt_spin_unlock+0x161/0x200
[  101.833315][ T5960]  ? __pfx_dtInsert+0x10/0x10 [jfs]
[  101.833391][ T5960]  ? txLock+0xaf9/0x1cb0 [jfs]
[  101.833477][ T5960]  ? dtInitRoot+0x22a/0x670 [jfs]
[  101.833556][ T5960]  jfs_mkdir+0x6ec/0xa70 [jfs]
[  101.833636][ T5960]  ? __pfx_jfs_mkdir+0x10/0x10 [jfs]
[  101.833721][ T5960]  ? generic_permission+0x2e5/0x690
[  101.833760][ T5960]  ? bpf_lsm_inode_mkdir+0x9/0x20
[  101.833776][ T5960]  vfs_mkdir+0x306/0x510
[  101.833786][ T5960]  do_mkdirat+0x247/0x590
[  101.833795][ T5960]  ? __pfx_do_mkdirat+0x10/0x10
[  101.833804][ T5960]  ? getname_flags+0x1e5/0x540
[  101.833815][ T5960]  __x64_sys_mkdir+0x6c/0x80
[  101.833823][ T5960]  do_syscall_64+0xfa/0xfa0
[  101.833832][ T5960]  ? lockdep_hardirqs_on+0x9c/0x150
[  101.833840][ T5960]  ? entry_SYSCALL_64_after_hwframe+0x77/0x7f
[  101.833847][ T5960]  ? exc_page_fault+0xab/0x100
[  101.833856][ T5960]  entry_SYSCALL_64_after_hwframe+0x77/0x7f

Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>

0 files changed, 0 insertions, 0 deletions