jfs: add dmapctl integrity check to prevent invalid operations

jfs: add dmapctl integrity check to prevent invalid operations

Add check_dmapctl() to validate dmapctl structure integrity, focusing on
preventing invalid operations caused by on-disk corruption.

Key checks:
 - nleafs bounded by [0, LPERCTL] (maximum leaf nodes per dmapctl).
 - l2nleafs bounded by [0, L2LPERCTL] and consistent with nleafs
   (nleafs must be 2^l2nleafs).
 - leafidx must be exactly CTLLEAFIND (expected leaf index position).
 - height bounded by [0, L2LPERCTL >> 1] (valid tree height range).
 - budmin validity: NOFREE only if nleafs=0; otherwise >= BUDMIN.
 - Leaf nodes fit within stree array (leafidx + nleafs <= CTLTREESIZE).
 - Leaf node values are either non-negative or NOFREE.

Invoked in dbAllocAG(), dbFindCtl(), dbAdjCtl() and dbExtendFS() when
accessing dmapctl pages, catching corruption early before dmap operations
trigger invalid memory access or logic errors.

This fixes the following UBSAN warning.

[58245.668090][T14017] ------------[ cut here ]------------
[58245.668103][T14017] UBSAN: shift-out-of-bounds in fs/jfs/jfs_dmap.c:2641:11
[58245.668119][T14017] shift exponent 110 is too large for 32-bit type 'int'
[58245.668137][T14017] CPU: 0 UID: 0 PID: 14017 Comm: 4c1966e88c28fa9 Tainted: G            E       6.18.0-rc4-00253-g21ce5d4ba045-dirty #124 PREEMPT_{RT,(full)}
[58245.668174][T14017] Tainted: [E]=UNSIGNED_MODULE
[58245.668176][T14017] Hardware name: QEMU Ubuntu 25.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[58245.668184][T14017] Call Trace:
[58245.668200][T14017]  <TASK>
[58245.668208][T14017]  dump_stack_lvl+0x189/0x250
[58245.668288][T14017]  ? __pfx_dump_stack_lvl+0x10/0x10
[58245.668301][T14017]  ? __pfx__printk+0x10/0x10
[58245.668315][T14017]  ? lock_metapage+0x303/0x400 [jfs]
[58245.668406][T14017]  ubsan_epilogue+0xa/0x40
[58245.668422][T14017]  __ubsan_handle_shift_out_of_bounds+0x386/0x410
[58245.668462][T14017]  dbSplit+0x1f8/0x200 [jfs]
[58245.668543][T14017]  dbAdjCtl+0x34c/0xa20 [jfs]
[58245.668628][T14017]  dbAllocNear+0x2ee/0x3d0 [jfs]
[58245.668710][T14017]  dbAlloc+0x933/0xba0 [jfs]
[58245.668797][T14017]  ea_write+0x374/0xdd0 [jfs]
[58245.668888][T14017]  ? __pfx_ea_write+0x10/0x10 [jfs]
[58245.668966][T14017]  ? __jfs_setxattr+0x76e/0x1120 [jfs]
[58245.669046][T14017]  __jfs_setxattr+0xa01/0x1120 [jfs]
[58245.669135][T14017]  ? __pfx___jfs_setxattr+0x10/0x10 [jfs]
[58245.669216][T14017]  ? mutex_lock_nested+0x154/0x1d0
[58245.669252][T14017]  ? __jfs_xattr_set+0xb9/0x170 [jfs]
[58245.669333][T14017]  __jfs_xattr_set+0xda/0x170 [jfs]
[58245.669430][T14017]  ? __pfx___jfs_xattr_set+0x10/0x10 [jfs]
[58245.669509][T14017]  ? xattr_full_name+0x6f/0x90
[58245.669546][T14017]  ? jfs_xattr_set+0x33/0x60 [jfs]
[58245.669636][T14017]  ? __pfx_jfs_xattr_set+0x10/0x10 [jfs]
[58245.669726][T14017]  __vfs_setxattr+0x43c/0x480
[58245.669743][T14017]  __vfs_setxattr_noperm+0x12d/0x660
[58245.669756][T14017]  vfs_setxattr+0x16b/0x2f0
[58245.669768][T14017]  ? __pfx_vfs_setxattr+0x10/0x10
[58245.669782][T14017]  filename_setxattr+0x274/0x600
[58245.669795][T14017]  ? __pfx_filename_setxattr+0x10/0x10
[58245.669806][T14017]  ? getname_flags+0x1e5/0x540
[58245.669829][T14017]  path_setxattrat+0x364/0x3a0
[58245.669840][T14017]  ? __pfx_path_setxattrat+0x10/0x10
[58245.669859][T14017]  ? __se_sys_chdir+0x1b9/0x280
[58245.669876][T14017]  __x64_sys_lsetxattr+0xbf/0xe0
[58245.669888][T14017]  do_syscall_64+0xfa/0xfa0
[58245.669901][T14017]  ? lockdep_hardirqs_on+0x9c/0x150
[58245.669913][T14017]  ? entry_SYSCALL_64_after_hwframe+0x77/0x7f
[58245.669927][T14017]  ? exc_page_fault+0xab/0x100
[58245.669937][T14017]  entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported-by: syzbot+4c1966e88c28fa96e053@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=4c1966e88c28fa96e053
Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>