| Message ID | 20230928204440.543-1-andrew.kanner@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net-next,v1] net/xdp: fix zero-size allocation warning in xskq_create() | expand |
From: Andrew Kanner <andrew.kanner@gmail.com> Date: Thu, 28 Sep 2023 23:44:40 +0300 > Syzkaller reported the following issue: [...] > 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 | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/net/xdp/xsk_queue.c b/net/xdp/xsk_queue.c > index f8905400ee07..1bc7fb1f14ae 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 (size == SIZE_MAX) unlikely(). > + return NULL; > + > size = PAGE_ALIGN(size); > > q->ring = vmalloc_user(size); Thanks, Olek
On Mon, Oct 02, 2023 at 03:52:44PM +0200, Alexander Lobakin wrote: > From: Andrew Kanner <andrew.kanner@gmail.com> > Date: Thu, 28 Sep 2023 23:44:40 +0300 > > > Syzkaller reported the following issue: > > [...] > > > 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 | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/net/xdp/xsk_queue.c b/net/xdp/xsk_queue.c > > index f8905400ee07..1bc7fb1f14ae 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 (size == SIZE_MAX) > > unlikely(). > > > + return NULL; > > + > > size = PAGE_ALIGN(size); > > > > q->ring = vmalloc_user(size); > > Thanks, > Olek Thanks, Olek. That is a reasonable optimization, I'll add it in v2. -- pw-bot: cr Andrew Kanner
diff --git a/net/xdp/xsk_queue.c b/net/xdp/xsk_queue.c index f8905400ee07..1bc7fb1f14ae 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 (size == SIZE_MAX) + return NULL; + size = PAGE_ALIGN(size); q->ring = vmalloc_user(size);
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> --- 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 | 3 +++ 1 file changed, 3 insertions(+)