[ +Andrey ]
On 2/2/22 7:01 AM, Hou Tao wrote:
After commit 2fd3fb0be1d1 ("kasan, vmalloc: unpoison VM_ALLOC pages
after mapping"), non-VM_ALLOC mappings will be marked as accessible
in __get_vm_area_node() when KASAN is enabled. But now the flag for
ringbuf area is VM_ALLOC, so KASAN will complain out-of-bound access
after vmap() returns. Because the ringbuf area is created by mapping
allocated pages, so use VM_MAP instead.
After the change, info in /proc/vmallocinfo also changes from
[start]-[end] 24576 ringbuf_map_alloc+0x171/0x290 vmalloc user
to
[start]-[end] 24576 ringbuf_map_alloc+0x171/0x290 vmap user
Reported-by: syzbot+5ad567a418794b9b5983@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
v2:
* explain why VM_ALLOC will lead to vmalloc-oob access
Do you know which tree commit 2fd3fb0be1d1 is, looks like it's neither
in bpf nor in bpf-next tree at the moment.
Either way, I presume this fix should be routed via bpf tree rather
than bpf-next? (I can add Fixes tag while applying.)
* add Reported-by tag
v1: https://lore.kernel.org/bpf/CANUnq3a+sT_qtO1wNQ3GnLGN7FLvSSgvit2UVgqQKRpUvs85VQ@xxxxxxxxxxxxxx/T/#t
---
kernel/bpf/ringbuf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c
index 638d7fd7b375..710ba9de12ce 100644
--- a/kernel/bpf/ringbuf.c
+++ b/kernel/bpf/ringbuf.c
@@ -104,7 +104,7 @@ static struct bpf_ringbuf *bpf_ringbuf_area_alloc(size_t data_sz, int numa_node)
}
rb = vmap(pages, nr_meta_pages + 2 * nr_data_pages,
- VM_ALLOC | VM_USERMAP, PAGE_KERNEL);
+ VM_MAP | VM_USERMAP, PAGE_KERNEL);
if (rb) {
kmemleak_not_leak(pages);
rb->pages = pages;
