Re: [PATCH RFC bpf-next 3/8] bpf: add BPF_JIT_KASAN for KASAN instrumentation of JITed programs

Alexis Lothoré
2026-04-14T13:24:25Z

On Tue Apr 14, 2026 at 12:20 AM CEST, Andrey Konovalov wrote:
> On Mon, Apr 13, 2026 at 8:29 PM Alexis Lothoré (eBPF Foundation)
> <alexis.lothore@bootlin.com> wrote:
>>
>> Add a new Kconfig option CONFIG_BPF_JIT_KASAN that automatically enables
>> KASAN (Kernel Address Sanitizer) memory access checks for JIT-compiled
>> BPF programs, when both KASAN and JIT compiler are enabled. When
>> enabled, the JIT compiler will emit shadow memory checks before memory
>> loads and stores to detect use-after-free, out-of-bounds, and other
>> memory safety bugs at runtime. The option is gated behind
>> HAVE_EBPF_JIT_KASAN, as it needs proper arch-specific implementation.
>>
>> Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
>> ---
>> kernel/bpf/Kconfig | 9 +++++++++
>> 1 file changed, 9 insertions(+)
>>
>> diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig
>> index eb3de35734f0..28392adb3d7e 100644
>> --- a/kernel/bpf/Kconfig
>> +++ b/kernel/bpf/Kconfig
>> @@ -17,6 +17,10 @@ config HAVE_CBPF_JIT
>> config HAVE_EBPF_JIT
>> bool
>>
>> +# KASAN support for JIT compiler
>> +config HAVE_EBPF_JIT_KASAN
>> + bool
>> +
>> # Used by archs to tell that they want the BPF JIT compiler enabled by
>> # default for kernels that were compiled with BPF JIT support.
>> config ARCH_WANT_DEFAULT_BPF_JIT
>> @@ -101,4 +105,9 @@ config BPF_LSM
>>
>> If you are unsure how to answer this question, answer N.
>>
>> +config BPF_JIT_KASAN
>> + bool
>> + depends on HAVE_EBPF_JIT_KASAN
>> + default y if BPF_JIT && KASAN_GENERIC
>
> Should this be "depends on KASAN && KASAN_GENERIC"?

Meaning, making it an explicit user-selectable option ?

If so, the current design choice is voluntary and based on the feedback
received on the original RFC, where I have been suggested to
automatically enable the KASAN instrumentation in BPF programs if KASAN
support is enabled in the kernel ([1]). But if a user-selectable toggle
is eventually a better solution, I'm fine with changing it.

[1] https://lore.kernel.org/bpf/CAADnVQLX7RSnOqQuU32Cgq-e0MVqyeNrtCQSBbk0W2xGkE-ZNw@mail.gmail.com/

>
>
>> +
>> endmenu # "BPF subsystem"
>>
>> --
>> 2.53.0
>>

--
Alexis Lothoré, Bootlin
Embedded Linux and Kernel engineering