CVE-2025-22056

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

netfilter: nft_tunnel: fix geneve_opt type confusion addition

When handling multiple NFTA_TUNNEL_KEY_OPTS_GENEVE attributes, the parsing logic should place every geneve_opt structure one by one compactly. Hence, when deciding the next geneve_opt position, the pointer addition should be in units of char *.

However, the current implementation erroneously does type conversion before the addition, which will lead to heap out-of-bounds write.

[ 6.989857] ================================================================== [ 6.990293] BUG: KASAN: slab-out-of-bounds in nft_tunnel_obj_init+0x977/0xa70 [ 6.990725] Write of size 124 at addr ffff888005f18974 by task poc/178 [ 6.991162] [ 6.991259] CPU: 0 PID: 178 Comm: poc-oob-write Not tainted 6.1.132 #1 [ 6.991655] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 [ 6.992281] Call Trace: [ 6.992423] [ 6.992586] dump_stack_lvl+0x44/0x5c [ 6.992801] print_report+0x184/0x4be [ 6.993790] kasan_report+0xc5/0x100 [ 6.994252] kasan_check_range+0xf3/0x1a0 [ 6.994486] memcpy+0x38/0x60 [ 6.994692] nft_tunnel_obj_init+0x977/0xa70 [ 6.995677] nft_obj_init+0x10c/0x1b0 [ 6.995891] nf_tables_newobj+0x585/0x950 [ 6.996922] nfnetlink_rcv_batch+0xdf9/0x1020 [ 6.998997] nfnetlink_rcv+0x1df/0x220 [ 6.999537] netlink_unicast+0x395/0x530 [ 7.000771] netlink_sendmsg+0x3d0/0x6d0 [ 7.001462] __sock_sendmsg+0x99/0xa0 [ 7.001707] ____sys_sendmsg+0x409/0x450 [ 7.002391] ___sys_sendmsg+0xfd/0x170 [ 7.003145] __sys_sendmsg+0xea/0x170 [ 7.004359] do_syscall_64+0x5e/0x90 [ 7.005817] entry_SYSCALL_64_after_hwframe+0x6e/0xd8 [ 7.006127] RIP: 0033:0x7ec756d4e407 [ 7.006339] Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 faf [ 7.007364] RSP: 002b:00007ffed5d46760 EFLAGS: 00000202 ORIG_RAX: 000000000000002e [ 7.007827] RAX: ffffffffffffffda RBX: 00007ec756cc4740 RCX: 00007ec756d4e407 [ 7.008223] RDX: 0000000000000000 RSI: 00007ffed5d467f0 RDI: 0000000000000003 [ 7.008620] RBP: 00007ffed5d468a0 R08: 0000000000000000 R09: 0000000000000000 [ 7.009039] R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000 [ 7.009429] R13: 00007ffed5d478b0 R14: 00007ec756ee5000 R15: 00005cbd4e655cb8

Fix this bug with correct pointer addition and conversion in parse and dump code.

Weakness

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

Affected Software

Potential Mitigations

• Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

• For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer.

• Be wary that a language’s interface to native code may still be subject to overflows, even if the language itself is theoretically safe.

• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

• Examples include the Safe C String Library (SafeStr) by Messier and Viega [REF-57], and the Strsafe.h library from Microsoft [REF-56]. These libraries provide safer versions of overflow-prone string-handling functions.

• Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.

• D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.

• Consider adhering to the following rules when allocating and managing an application’s memory:

• Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.

• Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.

• For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].

• Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [REF-60] [REF-61]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment.

• For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [REF-1336].

References

• https://git.kernel.org/stable/c/0a93a710d6df334b828ea064c6d39fda34f901dc
• https://git.kernel.org/stable/c/1b755d8eb1ace3870789d48fbd94f386ad6e30be
• https://git.kernel.org/stable/c/28d88ee1e1cc8ac2d79aeb112717b97c5c833d43
• https://git.kernel.org/stable/c/31d49eb436f2da61280508d7adf8c9b473b967aa
• https://git.kernel.org/stable/c/446d94898c560ed2f61e26ae445858a4c4830762
• https://git.kernel.org/stable/c/708e268acb3a446ad2a8a3d2e9bd41cc23660cd6
• https://git.kernel.org/stable/c/a263d31c8c92e5919d41af57d9479cfb66323782
• https://git.kernel.org/stable/c/ca2adfc03cd6273f0b589fe65afc6f75e0fe116e