[bug report] kho: update FDT dynamically for subtree addition/removal

[bug report] kho: update FDT dynamically for subtree addition/removal

[Dan Carpenter]

[ Smatch checking is paused while we raise funding. #SadFace
  https://lore.kernel.org/all/aTaiGSbWZ9DJaGo7@stanley.mountain/ -dan ]

Hello Pasha Tatashin,

Commit 8e068a286aef ("kho: update FDT dynamically for subtree
addition/removal") from Nov 14, 2025 (linux-next), leads to the
following Smatch static checker warning:

	kernel/liveupdate/kexec_handover.c:777 kho_add_subtree()
	warn: return mixup? 'err' vs 'fdt_err'

kernel/liveupdate/kexec_handover.c
    767 {
    768         phys_addr_t phys = virt_to_phys(fdt);
    769         void *root_fdt = kho_out.fdt;
    770         int err = -ENOMEM;
    771         int off, fdt_err;
    772 
    773         guard(mutex)(&kho_out.lock);
    774 
    775         fdt_err = fdt_open_into(root_fdt, root_fdt, PAGE_SIZE);
    776         if (fdt_err < 0)
--> 777                 return err;

Why return err (-ENOMEM) here instead of fdt_err?

    778 
    779         off = fdt_add_subnode(root_fdt, 0, name);
    780         if (off < 0) {
    781                 if (off == -FDT_ERR_EXISTS)
    782                         err = -EEXIST;
    783                 goto out_pack;
    784         }
    785 
    786         err = fdt_setprop(root_fdt, off, KHO_FDT_SUB_TREE_PROP_NAME,
    787                           &phys, sizeof(phys));
    788         if (err < 0)
    789                 goto out_pack;
    790 
    791         WARN_ON_ONCE(kho_debugfs_fdt_add(&kho_out.dbg, name, fdt, false));
    792 
    793 out_pack:
    794         fdt_pack(root_fdt);
    795 
    796         return err;
    797 }

regards,
dan carpenter