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> --- 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
