| From 3ccfb3d50b5bec53dc73a378e504e92dd598d1bd Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Mon, 19 Jul 2021 09:51:34 +0100 |
| Subject: bpf: Fix OOB read when printing XDP link fdinfo |
| |
| From: Lorenz Bauer <lmb@cloudflare.com> |
| |
| [ Upstream commit d6371c76e20d7d3f61b05fd67b596af4d14a8886 ] |
| |
| We got the following UBSAN report on one of our testing machines: |
| |
| ================================================================================ |
| UBSAN: array-index-out-of-bounds in kernel/bpf/syscall.c:2389:24 |
| index 6 is out of range for type 'char *[6]' |
| CPU: 43 PID: 930921 Comm: systemd-coredum Tainted: G O 5.10.48-cloudflare-kasan-2021.7.0 #1 |
| Hardware name: <snip> |
| Call Trace: |
| dump_stack+0x7d/0xa3 |
| ubsan_epilogue+0x5/0x40 |
| __ubsan_handle_out_of_bounds.cold+0x43/0x48 |
| ? seq_printf+0x17d/0x250 |
| bpf_link_show_fdinfo+0x329/0x380 |
| ? bpf_map_value_size+0xe0/0xe0 |
| ? put_files_struct+0x20/0x2d0 |
| ? __kasan_kmalloc.constprop.0+0xc2/0xd0 |
| seq_show+0x3f7/0x540 |
| seq_read_iter+0x3f8/0x1040 |
| seq_read+0x329/0x500 |
| ? seq_read_iter+0x1040/0x1040 |
| ? __fsnotify_parent+0x80/0x820 |
| ? __fsnotify_update_child_dentry_flags+0x380/0x380 |
| vfs_read+0x123/0x460 |
| ksys_read+0xed/0x1c0 |
| ? __x64_sys_pwrite64+0x1f0/0x1f0 |
| do_syscall_64+0x33/0x40 |
| entry_SYSCALL_64_after_hwframe+0x44/0xa9 |
| <snip> |
| ================================================================================ |
| ================================================================================ |
| UBSAN: object-size-mismatch in kernel/bpf/syscall.c:2384:2 |
| |
| From the report, we can infer that some array access in bpf_link_show_fdinfo at index 6 |
| is out of bounds. The obvious candidate is bpf_link_type_strs[BPF_LINK_TYPE_XDP] with |
| BPF_LINK_TYPE_XDP == 6. It turns out that BPF_LINK_TYPE_XDP is missing from bpf_types.h |
| and therefore doesn't have an entry in bpf_link_type_strs: |
| |
| pos: 0 |
| flags: 02000000 |
| mnt_id: 13 |
| link_type: (null) |
| link_id: 4 |
| prog_tag: bcf7977d3b93787c |
| prog_id: 4 |
| ifindex: 1 |
| |
| Fixes: aa8d3a716b59 ("bpf, xdp: Add bpf_link-based XDP attachment API") |
| Signed-off-by: Lorenz Bauer <lmb@cloudflare.com> |
| Signed-off-by: Andrii Nakryiko <andrii@kernel.org> |
| Link: https://lore.kernel.org/bpf/20210719085134.43325-2-lmb@cloudflare.com |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| include/linux/bpf_types.h | 1 + |
| 1 file changed, 1 insertion(+) |
| |
| diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h |
| index 2e6f568377f1..a8137bb6dd3c 100644 |
| --- a/include/linux/bpf_types.h |
| +++ b/include/linux/bpf_types.h |
| @@ -133,4 +133,5 @@ BPF_LINK_TYPE(BPF_LINK_TYPE_CGROUP, cgroup) |
| BPF_LINK_TYPE(BPF_LINK_TYPE_ITER, iter) |
| #ifdef CONFIG_NET |
| BPF_LINK_TYPE(BPF_LINK_TYPE_NETNS, netns) |
| +BPF_LINK_TYPE(BPF_LINK_TYPE_XDP, xdp) |
| #endif |
| -- |
| 2.30.2 |
| |