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(c.b.2.6.f.3.0.0.d.9.9.9.a.0.6.5.f.f.6.2.a.5.a.7.0.b.8.0.1.0.0.2.ip6.arpa. [2001:8b0:7a5a:26ff:560a:999d:3f:62bc]) by smtp.gmail.com with ESMTPSA id l14sm9130706wrs.22.2021.07.16.03.05.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Jul 2021 03:05:48 -0700 (PDT) From: Lorenz Bauer To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , "David S. Miller" , Jakub Kicinski , Jesper Dangaard Brouer , John Fastabend Cc: kernel-team@cloudflare.com, Lorenz Bauer , Andrii Nakryiko , netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH bpf] bpf: fix OOB read when printing XDP link fdinfo Date: Fri, 16 Jul 2021 11:04:52 +0100 Message-Id: <20210716100452.113652-1-lmb@cloudflare.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net 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: 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 ================================================================================ ================================================================================ 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 Acked-by: Andrii Nakryiko --- 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 a9db1eae6796..be95f2722ad9 100644 --- a/include/linux/bpf_types.h +++ b/include/linux/bpf_types.h @@ -135,3 +135,4 @@ BPF_LINK_TYPE(BPF_LINK_TYPE_ITER, iter) #ifdef CONFIG_NET BPF_LINK_TYPE(BPF_LINK_TYPE_NETNS, netns) #endif +BPF_LINK_TYPE(BPF_LINK_TYPE_XDP, xdp)