Re: [PATCH bpf-next 0/4] Use correct destructor kfunc types

On 7/25/25 9:22 AM, Sami Tolvanen wrote:

Hi,

On Fri, Jul 25, 2025 at 9:05 AM Yonghong Song [off-list ref] wrote:

quoted

I tried your patch set on top of latest bpf-next. The problem
still exists with the following error:

[   71.976265] CFI failure at bpf_obj_free_fields+0x298/0x620 (target: __bpf_crypto_ctx_release+0x0/0x10; expected type: 0xc1113566)
[   71.980134] Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
...


The following is the CFI related config items:

$ grep CFI .config
CONFIG_CFI_AUTO_DEFAULT=y
CONFIG_FUNCTION_PADDING_CFI=11
CONFIG_ARCH_SUPPORTS_CFI_CLANG=y
CONFIG_ARCH_USES_CFI_TRAPS=y
CONFIG_CFI_CLANG=y
# CONFIG_CFI_ICALL_NORMALIZE_INTEGERS is not set
CONFIG_HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG=y
CONFIG_HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC=y
# CONFIG_CFI_PERMISSIVE is not set

Did I miss anything?

Interesting. I tested this on arm64 and confirmed that the issue is
fixed there, so I wonder if we need to use KCFI_REFERENCE() here to
make sure objtool / x86 runtime patching knows this function actually
indirectly called. I'll test this on x86 and see what's going on.

I just tried arm64 with your patch set. CFI crash still happened:

CFI failure at tcp_ack+0xe74/0x13cc (target: bpf__tcp_congestion_ops_in_ack_event+0x0/0x78; expected type: 0x64424
87a)
Internal error: Oops - CFI: 00000000f2008228 [#1]  SMP
Modules linked in: bpf_testmod(OE) [last unloaded: bpf_testmod(OE)]
CPU: 0 UID: 0 PID: 152 Comm: test_progs Tainted: G           OE       6.16.0-rc6-g95993dc3039e-dirty #162 NONE
Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
Hardware name: linux,dummy-virt (DT)
pstate: 33400005 (nzCV daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : tcp_ack+0xe74/0x13cc
lr : tcp_ack+0xe34/0x13cc

The arm64 CFI related config:
$ cat .config | grep CFI
CONFIG_AS_HAS_CFI_NEGATE_RA_STATE=y
CONFIG_ARCH_SUPPORTS_CFI_CLANG=y
CONFIG_CFI_CLANG=y
# CONFIG_CFI_ICALL_NORMALIZE_INTEGERS is not set
CONFIG_HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG=y
# CONFIG_CFI_PERMISSIVE is not set

Thanks for taking a look!

Sami