On Mon, Dec 20, 2021 at 11:02:04PM +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(). > > Resetting tags for these pointers results in untagged pointers being > passed to set_memory_x(). This causes conflicts in arithmetic checks > in change_memory_common(), as vm_struct->addr pointer returned by > find_vm_area() is tagged. > > Reset pointer tag of find_vm_area(addr)->addr in change_memory_common(). > > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> > Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
