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Message-ID: <2f5abbf8-8d50-3deb-19cd-9bfd654e1ceb@iogearbox.net> Date: Thu, 5 Oct 2023 00:49:23 +0200 From: Daniel Borkmann <daniel@...earbox.net> To: Andrew Kanner <andrew.kanner@...il.com>, bjorn@...nel.org, magnus.karlsson@...el.com, maciej.fijalkowski@...el.com, jonathan.lemon@...il.com, davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, aleksander.lobakin@...el.com, xuanzhuo@...ux.alibaba.com, ast@...nel.org, hawk@...nel.org, john.fastabend@...il.com Cc: linux-kernel-mentees@...ts.linuxfoundation.org, netdev@...r.kernel.org, bpf@...r.kernel.org, linux-kernel@...r.kernel.org, syzbot+fae676d3cf469331fc89@...kaller.appspotmail.com Subject: Re: [PATCH net-next v2] net/xdp: fix zero-size allocation warning in xskq_create() On 10/3/23 12:29 AM, Andrew Kanner wrote: > 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@...kaller.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@...il.com> I guess also: Reported-by: syzbot+b132693e925cbbd89e26@...kaller.appspotmail.com Moreover, this fix is needed in bpf/net tree (as opposed to *-next tree), right? > net/xdp/xsk_queue.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/net/xdp/xsk_queue.c b/net/xdp/xsk_queue.c > index f8905400ee07..b03d1bfb6978 100644 > --- a/net/xdp/xsk_queue.c > +++ b/net/xdp/xsk_queue.c > @@ -34,6 +34,9 @@ struct xsk_queue *xskq_create(u32 nentries, bool umem_queue) > q->ring_mask = nentries - 1; > > size = xskq_get_ring_size(q, umem_queue); > + if (unlikely(size == SIZE_MAX)) > + return NULL; Doesn't this leak q here ? > size = PAGE_ALIGN(size); > > q->ring = vmalloc_user(size); >
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