On Sat, 7 Oct 2023 at 09:52, Andrew Kanner <andrew.kanner@xxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxxxxxxx > Closes: https://lore.kernel.org/all/000000000000c84b4705fb31741e@xxxxxxxxxx/T/ > Link: https://syzkaller.appspot.com/bug?extid=fae676d3cf469331fc89 > Reported-by: syzbot+b132693e925cbbd89e26@xxxxxxxxxxxxxxxxxxxxxxxxx > Closes: https://lore.kernel.org/all/000000000000e20df20606ebab4f@xxxxxxxxxx/T/ > Fixes: 9f78bf330a66 ("xsk: support use vaddr as ring") > Signed-off-by: Andrew Kanner <andrew.kanner@xxxxxxxxx> Thanks Andrew for fixing this. Acked-by: Magnus Karlsson <magnus.karlsson@xxxxxxxxx> > --- > > Notes (akanner): > v4: > - add explanation about SIZE_MAX, suggested by Martin KaFai Lau > <martin.lau@xxxxxxxxx> > v3: https://lore.kernel.org/all/20231005193548.515-1-andrew.kanner@xxxxxxxxx/T/ > - free kzalloc-ed memory before return, the leak was noticed by > Daniel Borkmann <daniel@xxxxxxxxxxxxx> > v2: https://lore.kernel.org/all/20231002222939.1519-1-andrew.kanner@xxxxxxxxx/raw > - use unlikely() optimization for the case with SIZE_MAX return from > struct_size(), suggested by Alexander Lobakin > <aleksander.lobakin@xxxxxxxxx> > - cc-ed 4 more maintainers, mentioned by cc_maintainers patchwork > test > > v1: https://lore.kernel.org/all/20230928204440.543-1-andrew.kanner@xxxxxxxxx/T/ > - RFC notes: > It was found that net/xdp/xsk.c:xsk_setsockopt() uses > copy_from_sockptr() to get the number of entries (int) for cases > with XDP_RX_RING / XDP_TX_RING and XDP_UMEM_FILL_RING / > XDP_UMEM_COMPLETION_RING. > > Next in xsk_init_queue() there're 2 sanity checks (entries == 0) > and (!is_power_of_2(entries)) for which -EINVAL will be returned. > > After that net/xdp/xsk_queue.c:xskq_create() will calculate the > size multipling the number of entries (int) with the size of u64, > at least. > > I wonder if there should be the upper bound (e.g. the 3rd sanity > check inside xsk_init_queue()). It seems that without the upper > limit it's quiet easy to overflow the allocated size (SIZE_MAX), > especially for 32-bit architectures, for example arm nodes which > were used by the syzkaller. > > In this patch I added a naive check for SIZE_MAX which helped to > skip zero-size allocation after overflow, but maybe it's not quite > right. Please, suggest if you have any thoughts about the > appropriate limit for the size of these xdp rings. > > PS: the initial number of entries is 0x20000000 in syzkaller > repro: syscall(__NR_setsockopt, (intptr_t)r[0], 0x11b, 3, > 0x20000040, 0x20); > > Link: > https://syzkaller.appspot.com/text?tag=ReproC&x=10910f18280000 > > net/xdp/xsk_queue.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/net/xdp/xsk_queue.c b/net/xdp/xsk_queue.c > index f8905400ee07..d2c264030017 100644 > --- a/net/xdp/xsk_queue.c > +++ b/net/xdp/xsk_queue.c > @@ -34,6 +34,16 @@ struct xsk_queue *xskq_create(u32 nentries, bool umem_queue) > q->ring_mask = nentries - 1; > > size = xskq_get_ring_size(q, umem_queue); > + > + /* size which is overflowing or close to SIZE_MAX will become 0 in > + * PAGE_ALIGN(), checking SIZE_MAX is enough due to the previous > + * is_power_of_2(), the rest will be handled by vmalloc_user() > + */ > + if (unlikely(size == SIZE_MAX)) { > + kfree(q); > + return NULL; > + } > + > size = PAGE_ALIGN(size); > > q->ring = vmalloc_user(size); > -- > 2.39.3 > >
