Messages in this thread | | | From | Eric Dumazet <> | Date | Thu, 27 Jan 2022 18:30:00 -0800 | Subject | Re: [PATCH net] net: dev: Detect dev_hold() after netdev_wait_allrefs() |
| |
On Thu, Jan 27, 2022 at 6:27 PM Jann Horn <jannh@google.com> wrote: > > I like that idea... but this_cpu_dec()/this_cpu_inc() use GS-relative > addressing, at least on X86-64, so NULL might make things worse, I > think? /proc/kallsyms on my machine starts with: > > 0000000000000000 A fixed_percpu_data > 0000000000000000 A __per_cpu_start > 0000000000001000 A cpu_debug_store > 0000000000002000 A irq_stack_backing_store > 0000000000006000 A cpu_tss_rw > 000000000000b000 A gdt_page > 000000000000c000 A exception_stacks > 0000000000010000 A entry_stack_storage > 0000000000011000 A espfix_waddr > > So we'd probably need some different placeholder instead of NULL to > actually crash...
Orthogonal problem, maybe we should make sure the first page of per-cpu data is un-mapped.
| |