bpf: Use VM_MAP instead of VM_ALLOC for ringbuf

commit b293dcc473d22a62dc6d78de2b15e4f49515db56 upstream.

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

Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it")
Reported-by: syzbot+5ad567a418794b9b5983@syzkaller.appspotmail.com
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220202060158.6260-1-houtao1@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c
index 9e0c10c6892ad9df08fa1809bf626e9097cbdf74..f1c51c45667d372f57244cb7da6ca72f1af96c1a 100644 (file)
--- 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;