Re: [PATCH net-next v2] net/xdp: fix zero-size allocation warning in xskq_create()

[Alexander Lobakin <aleksander.lobakin@intel.com>]

From: Andrew Kanner <andrew.kanner@gmail.com>
Date: Tue,  3 Oct 2023 01:29:40 +0300

> Syzkaller reported the following issue:
>  ------------[ cut here ]------------
>  WARNING: CPU: 0 PID: 2807 at mm/vmalloc.c:3247 __vmalloc_node_range (mm/vmalloc.c:3361)
>  Modules linked in:
>  CPU: 0 PID: 2807 Comm: repro Not tainted 6.6.0-rc2+ #12
>  Hardware name: Generic DT based system
>  unwind_backtrace from show_stack (arch/arm/kernel/traps.c:258)
>  show_stack from dump_stack_lvl (lib/dump_stack.c:107 (discriminator 1))
>  dump_stack_lvl from __warn (kernel/panic.c:633 kernel/panic.c:680)
>  __warn from warn_slowpath_fmt (./include/linux/context_tracking.h:153 kernel/panic.c:700)
>  warn_slowpath_fmt from __vmalloc_node_range (mm/vmalloc.c:3361 (discriminator 3))
>  __vmalloc_node_range from vmalloc_user (mm/vmalloc.c:3478)
>  vmalloc_user from xskq_create (net/xdp/xsk_queue.c:40)
>  xskq_create from xsk_setsockopt (net/xdp/xsk.c:953 net/xdp/xsk.c:1286)
>  xsk_setsockopt from __sys_setsockopt (net/socket.c:2308)
>  __sys_setsockopt from ret_fast_syscall (arch/arm/kernel/entry-common.S:68)
> 
> xskq_get_ring_size() uses struct_size() macro to safely calculate the
> size of struct xsk_queue and q->nentries of desc members. But the
> syzkaller repro was able to set q->nentries with the value initially
> taken from copy_from_sockptr() high enough to return SIZE_MAX by
> struct_size(). The next PAGE_ALIGN(size) is such case will overflow
> the size_t value and set it to 0. This will trigger WARN_ON_ONCE in
> vmalloc_user() -> __vmalloc_node_range().
> 
> The issue is reproducible on 32-bit arm kernel.
> 
> Reported-and-tested-by: syzbot+fae676d3cf469331fc89@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/all/000000000000c84b4705fb31741e@google.com/T/
> Link: https://syzkaller.appspot.com/bug?extid=fae676d3cf469331fc89
> Fixes: 9f78bf330a66 ("xsk: support use vaddr as ring")
> Signed-off-by: Andrew Kanner <andrew.kanner@gmail.com>

Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>

[...]

Thanks,
Olek