> Add a new Kconfig option CONFIG_BPF_JIT_KASAN that automatically enables
> generic KASAN (Kernel Address SANitizer) memory access checks for
> JIT-compiled BPF programs as well, when both KASAN_GENERIC and JIT
> compiler are enabled. This new Kconfig is not a user selectable one: it
> is either automatically enabled if KASAN is enabled on a compatible
> platform, or disabled. When enabled, the JIT compiler will emit shadow
> memory checks before memory loads and stores to detect use-after-free or
> out-of-bounds accesses at runtime. The option is gated behind
> HAVE_EBPF_JIT_KASAN, as it needs proper arch-specific implementation.
>
> As KASAN instrumentation for eBPF program will depend on the info that
> can be accessed during each instruction verification, there may be
> instructions that will be instrumented even if they don't really need to
> (eg: global subprograms that access caller stack memory passed as
> argument). To make sure that those additional checks do not trigger any
> crash, make sure that VMAP_STACK is enabled so that programs stack has
> shadow memory allocated.
>
> Signed-off-by: Alexis Lothoré (eBPF Foundation)
> <[email protected]>
This isn't a bug, but the changelog describes the enabling condition as
"KASAN_GENERIC and JIT compiler", while the added default line also
requires KASAN_VMALLOC:
config BPF_JIT_KASAN
bool
depends on HAVE_EBPF_JIT_KASAN
default y if BPF_JIT && KASAN_GENERIC && KASAN_VMALLOC &&
VMAP_STACK
Could the changelog state the full set of conditions that enable
BPF_JIT_KASAN (including KASAN_VMALLOC) so the described behavior matches
the "default y if" line?
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/28510424881
