Re: [PATCH mm v3 31/38] kasan, arm64: don't tag executable vmalloc allocations

[Catalin Marinas]

On Mon, Dec 13, 2021 at 10:54:27PM +0100, andrey.konovalov@xxxxxxxxx wrote:
> From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> 
> Besides asking vmalloc memory to be executable via the prot argument
> of __vmalloc_node_range() (see the previous patch), the kernel can skip
> that bit and instead mark memory as executable via set_memory_x().
> 
> Once tag-based KASAN modes start tagging vmalloc allocations, executing
> code from such allocations will lead to the PC register getting a tag,
> which is not tolerated by the kernel.
> 
> Generic kernel code typically allocates memory via module_alloc() if
> it intends to mark memory as executable. (On arm64 module_alloc()
> uses __vmalloc_node_range() without setting the executable bit).
> 
> Thus, reset pointer tags of pointers returned from module_alloc().
> 
> However, on arm64 there's an exception: the eBPF subsystem. Instead of
> using module_alloc(), it uses vmalloc() (via bpf_jit_alloc_exec())
> to allocate its JIT region.
> 
> Thus, reset pointer tags of pointers returned from bpf_jit_alloc_exec().
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>