Re: [PATCH bpf-next v7 0/9] bpf: add support for KASAN checks in JITed programs

[Ihor Solodrai <ihor.solodrai@linux.dev>]

On 2026-08-23 3:53 p.m., Kumar Kartikeya Dwivedi wrote:
> On Sat Aug 22, 2026 at 12:39 AM CEST, Alexis Lothoré (eBPF Foundation) wrote:
>> Hello,
>> this is v7 of the series aiming to bring basic support for KASAN checks
>> to BPF JITed programs. This new revision just makes the series rebased
>> on top of current bpf-next_base.
>>
>> Please note that with the recent kernel splat detector introduced in
>> kernel-patches/vmtest through commit 8109e5928cd0 ("ci: own the kernel
>> splat matching (#509)"), CI runs on this series will fail with the
>> following error.
>>
>>     Error: kernel splat detected: [  100.689549] BUG: KASAN: \
>>     slab-use-after-free in \
>>     bpf_prog_eba69524d1d949b1_st_not_on_stack+0x12f/0x17a \
>>
>> which is pretty normal, as the new selftests introduced by this series
>> are expected to trigger KASAN splats (the test_progs part will pass,
>> only the kernel_splats part will trigger errors). The right fix may be
>> to just put a list of regex matching all the kasan subtests progs in the
>> relevant SPLAT_ALLOWLIST file; something like:
>>
>> BUG: KASAN: slab-(out-of-bounds|use-after-free) in bpf_prog_([a-f0-9]){16}_(st|ld)(x)?(_not)?_on_stack\+
>> BUG: KASAN: slab-(out-of-bounds|use-after-free) in bpf_prog_([a-f0-9]){16}_simple_atomic(_fetch)?(_not)_on_stack\+
>> BUG: KASAN: slab-(out-of-bounds|use-after-free) in bpf_prog_([a-f0-9]){16}_ldx_patched(_not)?_on_stack\+
>> BUG: KASAN: slab-(out-of-bounds|use-after-free) in bpf_prog_([a-f0-9]){16}_verifier_paths_stack_and_non_stack\+
>> BUG: KASAN: slab-(out-of-bounds|use-after-free) in bpf_prog_([a-f0-9]){16}_ldx_oob\+
>> BUG: KASAN: slab-(out-of-bounds|use-after-free) in bpf_prog_([a-f0-9]){16}_st_blinded\+
>> BUG: KASAN: slab-(out-of-bounds|use-after-free) in bpf_prog_([a-f0-9]){16}_(load_acquire|store_release)(_not)?_on_stack\+
>>
>> I can take care of opening the relevant PR in kernel-patches/vmtest with
>> this if it ends up being the correct solution, but it will make sense to
>> do so only once the selftests list is validated (but before merging the
>> series).
> 
> We need to resolve this before landing the set. To me it looks inevitable, esp.
> if we exercise the support and produce such warnings. That said I'll let Ihor
> respond and provide guidance for this. We should probably land the vmtest PR
> before v8 is posted, so that v8 can go through CI and be processed without
> failures.

This is a tricky one.

IIUC the suggested allowlist regex will also mask the real splats, which
the whole KASAN-in-JIT project was supposed to catch.

I think a good way to resolve this is to teach the kasan splat
detection script about these tests, and drop/skip them from the dmesg
log it inspects. For example, match begin / end of the test set.
Might require special log anchors printed by the test itself, but
you get the idea.

Alexis, do you mind trying this?
> 
>> [...]