CVE-2024-56650: Out-of-bounds Read

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

netfilter: x_tables: fix LED ID check in led_tg_check()

Syzbot has reported the following BUG detected by KASAN:

BUG: KASAN: slab-out-of-bounds in strlen+0x58/0x70 Read of size 1 at addr ffff8881022da0c8 by task repro/5879 ... Call Trace: <TASK> dump_stack_lvl+0x241/0x360 ? __pfx_dump_stack_lvl+0x10/0x10 ? __pfx__printk+0x10/0x10 ? _printk+0xd5/0x120 ? __virt_addr_valid+0x183/0x530 ? __virt_addr_valid+0x183/0x530 print_report+0x169/0x550 ? __virt_addr_valid+0x183/0x530 ? __virt_addr_valid+0x183/0x530 ? __virt_addr_valid+0x45f/0x530 ? __phys_addr+0xba/0x170 ? strlen+0x58/0x70 kasan_report+0x143/0x180 ? strlen+0x58/0x70 strlen+0x58/0x70 kstrdup+0x20/0x80 led_tg_check+0x18b/0x3c0 xt_check_target+0x3bb/0xa40 ? __pfx_xt_check_target+0x10/0x10 ? stack_depot_save_flags+0x6e4/0x830 ? nft_target_init+0x174/0xc30 nft_target_init+0x82d/0xc30 ? __pfx_nft_target_init+0x10/0x10 ? nf_tables_newrule+0x1609/0x2980 ? nf_tables_newrule+0x1609/0x2980 ? rcu_is_watching+0x15/0xb0 ? nf_tables_newrule+0x1609/0x2980 ? nf_tables_newrule+0x1609/0x2980 ? __kmalloc_noprof+0x21a/0x400 nf_tables_newrule+0x1860/0x2980 ? __pfx_nf_tables_newrule+0x10/0x10 ? __nla_parse+0x40/0x60 nfnetlink_rcv+0x14e5/0x2ab0 ? __pfx_validate_chain+0x10/0x10 ? __pfx_nfnetlink_rcv+0x10/0x10 ? __lock_acquire+0x1384/0x2050 ? netlink_deliver_tap+0x2e/0x1b0 ? __pfx_lock_release+0x10/0x10 ? netlink_deliver_tap+0x2e/0x1b0 netlink_unicast+0x7f8/0x990 ? __pfx_netlink_unicast+0x10/0x10 ? __virt_addr_valid+0x183/0x530 ? __check_object_size+0x48e/0x900 netlink_sendmsg+0x8e4/0xcb0 ? __pfx_netlink_sendmsg+0x10/0x10 ? aa_sock_msg_perm+0x91/0x160 ? __pfx_netlink_sendmsg+0x10/0x10 __sock_sendmsg+0x223/0x270 ____sys_sendmsg+0x52a/0x7e0 ? __pfx_____sys_sendmsg+0x10/0x10 __sys_sendmsg+0x292/0x380 ? __pfx___sys_sendmsg+0x10/0x10 ? lockdep_hardirqs_on_prepare+0x43d/0x780 ? __pfx_lockdep_hardirqs_on_prepare+0x10/0x10 ? exc_page_fault+0x590/0x8c0 ? do_syscall_64+0xb6/0x230 do_syscall_64+0xf3/0x230 entry_SYSCALL_64_after_hwframe+0x77/0x7f ... </TASK>

Since an invalid (without '\0' byte at all) byte sequence may be passed from userspace, add an extra check to ensure that such a sequence is rejected as possible ID and so never passed to 'kstrdup()' and further.