[ Upstream commit 333291ce5055f2039afc907badaf5b66bc1adfdc ]

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 Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/arraymap.c | 7 ++++++- tools/testing/selftests/bpf/prog_tests/mmap.c | 9 +++++++++ 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index 95d77770353c..1d6120fd5ba6 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -486,7 +486,12 @@ static int array_map_mmap(struct bpf_map *map, struct vm_area_struct *vma) 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 = { diff --git a/tools/testing/selftests/bpf/prog_tests/mmap.c b/tools/testing/selftests/bpf/prog_tests/mmap.c index 16a814eb4d64..b0e789678aa4 100644 --- a/tools/testing/selftests/bpf/prog_tests/mmap.c +++ b/tools/testing/selftests/bpf/prog_tests/mmap.c @@ -197,6 +197,15 @@ void test_mmap(void) CHECK_FAIL(map_data->val[far] != 3 * 321);

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; + } + cleanup: if (bss_mmaped) CHECK_FAIL(munmap(bss_mmaped, bss_sz));