From: Andrii Nakryiko <andriin@fb.com>
Date: Tue, 12 May 2020 16:59:25 -0700
Subject: bpf: Fix bug in mmap() implementation for BPF array map
Patch-mainline: v5.7-rc6
Git-commit: 333291ce5055f2039afc907badaf5b66bc1adfdc
References: bsc#1154353

mmap() subsystem allows user-space application to memory-map region with
initial page offset. This wasn't taken into account in initial implementation
of BPF array memory-mapping. This would result in wrong pages, not taking into
account requested page shift, being memory-mmaped into user-space. This patch
fixes this gap and adds a test for such scenario.

Fixes: fc9702273e2e ("bpf: Add mmap() support for BPF_MAP_TYPE_ARRAY")
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200512235925.3817805-1-andriin@fb.com
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 kernel/bpf/arraymap.c                         |    7 ++++++-
 tools/testing/selftests/bpf/prog_tests/mmap.c |    8 ++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -486,7 +486,12 @@ static int array_map_mmap(struct bpf_map
 	if (!(map->map_flags & BPF_F_MMAPABLE))
 		return -EINVAL;
 
-	return remap_vmalloc_range(vma, array_map_vmalloc_addr(array), pgoff);
+	if (vma->vm_pgoff * PAGE_SIZE + (vma->vm_end - vma->vm_start) >
+	    PAGE_ALIGN((u64)array->map.max_entries * array->elem_size))
+		return -EINVAL;
+
+	return remap_vmalloc_range(vma, array_map_vmalloc_addr(array),
+				   vma->vm_pgoff + pgoff);
 }
 
 const struct bpf_map_ops array_map_ops = {
--- a/tools/testing/selftests/bpf/prog_tests/mmap.c
+++ b/tools/testing/selftests/bpf/prog_tests/mmap.c
@@ -230,6 +230,14 @@ void test_mmap(void)
 
 	munmap(tmp2, 4 * page_size);
 
+	/* map all 4 pages, but with pg_off=1 page, should fail */
+	tmp1 = mmap(NULL, 4 * page_size, PROT_READ, MAP_SHARED | MAP_FIXED,
+		    data_map_fd, page_size /* initial page shift */);
+	if (CHECK(tmp1 != MAP_FAILED, "adv_mmap7", "unexpected success")) {
+		munmap(tmp1, 4 * page_size);
+		goto cleanup;
+	}
+
 	tmp1 = mmap(NULL, map_sz, PROT_READ, MAP_SHARED, data_map_fd, 0);
 	if (CHECK(tmp1 == MAP_FAILED, "last_mmap", "failed %d\n", errno))
 		goto cleanup;