| Message ID | 20210716100452.113652-1-lmb@cloudflare.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf] bpf: fix OOB read when printing XDP link fdinfo | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for bpf |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | warning | 4 maintainers not CCed: songliubraving@fb.com yhs@fb.com kafai@fb.com kpsingh@kernel.org |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 11802 this patch: 11802 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 4 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 11304 this patch: 11304 |
| netdev/header_inline | success | Link |
On Fri, Jul 16, 2021 at 3:05 AM Lorenz Bauer <lmb@cloudflare.com> wrote: > > 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> > --- Well, oops. Thanks for the fix! Acked-by: Andrii Nakryiko <andrii@kernel.org> It would be great to have a compilation error for something like this. I wonder if we can do something to detect this going forward? > 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) > -- > 2.30.2 >
On 7/16/21 10:43 PM, Andrii Nakryiko wrote: > On Fri, Jul 16, 2021 at 3:05 AM Lorenz Bauer <lmb@cloudflare.com> wrote: >> >> 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> >> --- > > Well, oops. Thanks for the fix! > > Acked-by: Andrii Nakryiko <andrii@kernel.org> > > It would be great to have a compilation error for something like this. > I wonder if we can do something to detect this going forward? > >> 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) Lorenz, does this compile when you don't have CONFIG_NET configured? I would assume this needs to go right below the netns one depending on CONFIG_NET.. at least the bpf_xdp_link_lops are in net/core/dev.c which is only built under CONFIG_NET. Thanks, Daniel
On Fri, 16 Jul 2021 at 21:44, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote: > > Well, oops. Thanks for the fix! > > Acked-by: Andrii Nakryiko <andrii@kernel.org> > > It would be great to have a compilation error for something like this. > I wonder if we can do something to detect this going forward? I had a second patch that introduced MAX_BPF_LINK_TYPE, etc. and then added explicit array initializers: [MAX_BPF_LINK_TYPE] = NULL, That turns the OOB read into a NULL read. But it has to be done for every inclusion of bpf_types.h so it's a bit cumbersome. Maybe add MAX_BPF_LINK_TYPE and then add an entry in bpf_types.h for it as well? -- Lorenz Bauer | Systems Engineer 6th Floor, County Hall/The Riverside Building, SE1 7PB, UK www.cloudflare.com
On Fri, 16 Jul 2021 at 22:01, Daniel Borkmann <daniel@iogearbox.net> wrote: > > On 7/16/21 10:43 PM, Andrii Nakryiko wrote: > > On Fri, Jul 16, 2021 at 3:05 AM Lorenz Bauer <lmb@cloudflare.com> wrote: > >> > >> 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> > >> --- > > > > Well, oops. Thanks for the fix! > > > > Acked-by: Andrii Nakryiko <andrii@kernel.org> > > > > It would be great to have a compilation error for something like this. > > I wonder if we can do something to detect this going forward? > > > >> 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) > > Lorenz, does this compile when you don't have CONFIG_NET configured? I would assume > this needs to go right below the netns one depending on CONFIG_NET.. at least the > bpf_xdp_link_lops are in net/core/dev.c which is only built under CONFIG_NET. It does compile, since the only use of the macro is to stringify a link type for fdinfo. I'll move it into CONFIG_NET to be consistent with netdev though.
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)
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> --- include/linux/bpf_types.h | 1 + 1 file changed, 1 insertion(+)