CVE-2024-56650

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: 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 …

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.

Weakness

The product reads data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
• To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/540.html

References

• https://git.kernel.org/stable/c/04317f4eb2aad312ad85c1a17ad81fe75f1f9bc7
• https://git.kernel.org/stable/c/147a42bb02de8735cb08476be6d0917987d022c2
• https://git.kernel.org/stable/c/36a9d94dac28beef6b8abba46ba8874320d3e800
• https://git.kernel.org/stable/c/a9bcc0b70d9baf3ff005874489a0dc9d023b54c3
• https://git.kernel.org/stable/c/ab9916321c95f5280b72b4c5055e269f98627efe
• https://git.kernel.org/stable/c/ad28612ebae1fcc1104bd432e99e99d87f6bfe09
• https://git.kernel.org/stable/c/c40c96d98e536fc1daaa125c2332b988615e30a4