| Message ID | 20240216235536.it.234-kees@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2] bpf: Replace bpf_lpm_trie_key 0-length array with flexible array | expand |
On 2/16/24 17:55, Kees Cook wrote: > Replace deprecated 0-length array in struct bpf_lpm_trie_key with > flexible array. Found with GCC 13: > > ../kernel/bpf/lpm_trie.c:207:51: warning: array subscript i is outside array bounds of 'const __u8[0]' {aka 'const unsigned char[]'} [-Warray-bounds=] > 207 | *(__be16 *)&key->data[i]); > | ^~~~~~~~~~~~~ > ../include/uapi/linux/swab.h:102:54: note: in definition of macro '__swab16' > 102 | #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x)) > | ^ > ../include/linux/byteorder/generic.h:97:21: note: in expansion of macro '__be16_to_cpu' > 97 | #define be16_to_cpu __be16_to_cpu > | ^~~~~~~~~~~~~ > ../kernel/bpf/lpm_trie.c:206:28: note: in expansion of macro 'be16_to_cpu' > 206 | u16 diff = be16_to_cpu(*(__be16 *)&node->data[i] > ^ > | ^~~~~~~~~~~ > In file included from ../include/linux/bpf.h:7: > ../include/uapi/linux/bpf.h:82:17: note: while referencing 'data' > 82 | __u8 data[0]; /* Arbitrary size */ > | ^~~~ > > And found at run-time under CONFIG_FORTIFY_SOURCE: > > UBSAN: array-index-out-of-bounds in kernel/bpf/lpm_trie.c:218:49 > index 0 is out of range for type '__u8 [*]' > > This includes fixing the selftest which was incorrectly using a > variable length struct as a header, identified earlier[1]. Avoid this > by just explicitly including the prefixlen member instead of struct > bpf_lpm_trie_key. > > Note that it is not possible to simply remove the "data" member, as it > is referenced by userspace > > cilium: > struct egress_gw_policy_key in_key = { > .lpm_key = { 32 + 24, {} }, > .saddr = CLIENT_IP, > .daddr = EXTERNAL_SVC_IP & 0Xffffff, > }; > > systemd: > ipv6_map_fd = bpf_map_new( > BPF_MAP_TYPE_LPM_TRIE, > offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t)*4, > sizeof(uint64_t), > ... > > The only risk to UAPI would be if sizeof() were used directly on the > data member, which it does not seem to be. It is only used as a static > initializer destination and to find its location via offsetof(). > > Link: https://lore.kernel.org/all/202206281009.4332AA33@keescook/ [1] > Reported-by: Mark Rutland <mark.rutland@arm.com> > Closes: https://paste.debian.net/hidden/ca500597/ mmh... this URL expires: 2024-05-15 > Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: Gustavo A. R. Silva <gustavoars@kernel.org> Thanks! -- Gustavo > --- > Cc: Alexei Starovoitov <ast@kernel.org> > Cc: Daniel Borkmann <daniel@iogearbox.net> > Cc: Andrii Nakryiko <andrii@kernel.org> > Cc: Martin KaFai Lau <martin.lau@linux.dev> > Cc: Song Liu <song@kernel.org> > Cc: Yonghong Song <yhs@fb.com> > Cc: John Fastabend <john.fastabend@gmail.com> > Cc: KP Singh <kpsingh@kernel.org> > Cc: Stanislav Fomichev <sdf@google.com> > Cc: Hao Luo <haoluo@google.com> > Cc: Jiri Olsa <jolsa@kernel.org> > Cc: Mykola Lysenko <mykolal@fb.com> > Cc: Shuah Khan <shuah@kernel.org> > Cc: Haowen Bai <baihaowen@meizu.com> > Cc: bpf@vger.kernel.org > Cc: linux-kselftest@vger.kernel.org > > v2- clarify commit log, add more failure examples > v1- https://lore.kernel.org/all/63e531e3.170a0220.3a46a.3262@mx.google.com/ > --- > include/uapi/linux/bpf.h | 2 +- > tools/testing/selftests/bpf/progs/map_ptr_kern.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index 754e68ca8744..359dd8a429c1 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -80,7 +80,7 @@ struct bpf_insn { > /* Key of an a BPF_MAP_TYPE_LPM_TRIE entry */ > struct bpf_lpm_trie_key { > __u32 prefixlen; /* up to 32 for AF_INET, 128 for AF_INET6 */ > - __u8 data[0]; /* Arbitrary size */ > + __u8 data[]; /* Arbitrary size */ > }; > > struct bpf_cgroup_storage_key { > diff --git a/tools/testing/selftests/bpf/progs/map_ptr_kern.c b/tools/testing/selftests/bpf/progs/map_ptr_kern.c > index 3325da17ec81..1d476c6ae284 100644 > --- a/tools/testing/selftests/bpf/progs/map_ptr_kern.c > +++ b/tools/testing/selftests/bpf/progs/map_ptr_kern.c > @@ -316,7 +316,7 @@ struct lpm_trie { > } __attribute__((preserve_access_index)); > > struct lpm_key { > - struct bpf_lpm_trie_key trie_key; > + __u32 prefixlen; > __u32 data; > }; >
On Fri, Feb 16, 2024 at 06:27:08PM -0600, Gustavo A. R. Silva wrote: > > > On 2/16/24 17:55, Kees Cook wrote: > > Replace deprecated 0-length array in struct bpf_lpm_trie_key with > > flexible array. Found with GCC 13: > > > > ../kernel/bpf/lpm_trie.c:207:51: warning: array subscript i is outside array bounds of 'const __u8[0]' {aka 'const unsigned char[]'} [-Warray-bounds=] > > 207 | *(__be16 *)&key->data[i]); > > | ^~~~~~~~~~~~~ > > ../include/uapi/linux/swab.h:102:54: note: in definition of macro '__swab16' > > 102 | #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x)) > > | ^ > > ../include/linux/byteorder/generic.h:97:21: note: in expansion of macro '__be16_to_cpu' > > 97 | #define be16_to_cpu __be16_to_cpu > > | ^~~~~~~~~~~~~ > > ../kernel/bpf/lpm_trie.c:206:28: note: in expansion of macro 'be16_to_cpu' > > 206 | u16 diff = be16_to_cpu(*(__be16 *)&node->data[i] > > ^ > > | ^~~~~~~~~~~ > > In file included from ../include/linux/bpf.h:7: > > ../include/uapi/linux/bpf.h:82:17: note: while referencing 'data' > > 82 | __u8 data[0]; /* Arbitrary size */ > > | ^~~~ > > > > And found at run-time under CONFIG_FORTIFY_SOURCE: > > > > UBSAN: array-index-out-of-bounds in kernel/bpf/lpm_trie.c:218:49 > > index 0 is out of range for type '__u8 [*]' > > > > This includes fixing the selftest which was incorrectly using a > > variable length struct as a header, identified earlier[1]. Avoid this > > by just explicitly including the prefixlen member instead of struct > > bpf_lpm_trie_key. > > > > Note that it is not possible to simply remove the "data" member, as it > > is referenced by userspace > > > > cilium: > > struct egress_gw_policy_key in_key = { > > .lpm_key = { 32 + 24, {} }, > > .saddr = CLIENT_IP, > > .daddr = EXTERNAL_SVC_IP & 0Xffffff, > > }; > > > > systemd: > > ipv6_map_fd = bpf_map_new( > > BPF_MAP_TYPE_LPM_TRIE, > > offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t)*4, > > sizeof(uint64_t), > > ... > > > > The only risk to UAPI would be if sizeof() were used directly on the > > data member, which it does not seem to be. It is only used as a static > > initializer destination and to find its location via offsetof(). > > > > Link: https://lore.kernel.org/all/202206281009.4332AA33@keescook/ [1] > > Reported-by: Mark Rutland <mark.rutland@arm.com> > > Closes: https://paste.debian.net/hidden/ca500597/ > > mmh... this URL expires: 2024-05-15 Yup, but that's why I included the run-time splat above too. :)
On 2/17/24 4:03 AM, Kees Cook wrote: > On Fri, Feb 16, 2024 at 06:27:08PM -0600, Gustavo A. R. Silva wrote: >> On 2/16/24 17:55, Kees Cook wrote: >>> Replace deprecated 0-length array in struct bpf_lpm_trie_key with >>> flexible array. Found with GCC 13: >>> >>> ../kernel/bpf/lpm_trie.c:207:51: warning: array subscript i is outside array bounds of 'const __u8[0]' {aka 'const unsigned char[]'} [-Warray-bounds=] >>> 207 | *(__be16 *)&key->data[i]); >>> | ^~~~~~~~~~~~~ >>> ../include/uapi/linux/swab.h:102:54: note: in definition of macro '__swab16' >>> 102 | #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x)) >>> | ^ >>> ../include/linux/byteorder/generic.h:97:21: note: in expansion of macro '__be16_to_cpu' >>> 97 | #define be16_to_cpu __be16_to_cpu >>> | ^~~~~~~~~~~~~ >>> ../kernel/bpf/lpm_trie.c:206:28: note: in expansion of macro 'be16_to_cpu' >>> 206 | u16 diff = be16_to_cpu(*(__be16 *)&node->data[i] >>> ^ >>> | ^~~~~~~~~~~ >>> In file included from ../include/linux/bpf.h:7: >>> ../include/uapi/linux/bpf.h:82:17: note: while referencing 'data' >>> 82 | __u8 data[0]; /* Arbitrary size */ >>> | ^~~~ >>> >>> And found at run-time under CONFIG_FORTIFY_SOURCE: >>> >>> UBSAN: array-index-out-of-bounds in kernel/bpf/lpm_trie.c:218:49 >>> index 0 is out of range for type '__u8 [*]' >>> >>> This includes fixing the selftest which was incorrectly using a >>> variable length struct as a header, identified earlier[1]. Avoid this >>> by just explicitly including the prefixlen member instead of struct >>> bpf_lpm_trie_key. >>> >>> Note that it is not possible to simply remove the "data" member, as it >>> is referenced by userspace >>> >>> cilium: >>> struct egress_gw_policy_key in_key = { >>> .lpm_key = { 32 + 24, {} }, >>> .saddr = CLIENT_IP, >>> .daddr = EXTERNAL_SVC_IP & 0Xffffff, >>> }; >>> >>> systemd: >>> ipv6_map_fd = bpf_map_new( >>> BPF_MAP_TYPE_LPM_TRIE, >>> offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t)*4, >>> sizeof(uint64_t), >>> ... >>> >>> The only risk to UAPI would be if sizeof() were used directly on the >>> data member, which it does not seem to be. It is only used as a static >>> initializer destination and to find its location via offsetof(). >>> >>> Link: https://lore.kernel.org/all/202206281009.4332AA33@keescook/ [1] >>> Reported-by: Mark Rutland <mark.rutland@arm.com> >>> Closes: https://paste.debian.net/hidden/ca500597/ >> >> mmh... this URL expires: 2024-05-15 > > Yup, but that's why I included the run-time splat above too. :) I don't quite follow, this basically undoes 3024d95a4c52 ("bpf: Partially revert flexible-array member replacement") again with the small change that this 'fixes' up the BPF selftest to not embed struct bpf_lpm_trie_key. Outside of BPF selftests though aren't we readding the same error that we fixed earlier for BPF programs in the wild which embed struct bpf_lpm_trie_key into their key structure? Thanks, Daniel
On Mon, Feb 19, 2024 at 06:48:41PM +0100, Daniel Borkmann wrote: > On 2/17/24 4:03 AM, Kees Cook wrote: > > On Fri, Feb 16, 2024 at 06:27:08PM -0600, Gustavo A. R. Silva wrote: > > > On 2/16/24 17:55, Kees Cook wrote: > > > > Replace deprecated 0-length array in struct bpf_lpm_trie_key with > > > > flexible array. Found with GCC 13: > > > > > > > > ../kernel/bpf/lpm_trie.c:207:51: warning: array subscript i is outside array bounds of 'const __u8[0]' {aka 'const unsigned char[]'} [-Warray-bounds=] > > > > 207 | *(__be16 *)&key->data[i]); > > > > | ^~~~~~~~~~~~~ > > > > ../include/uapi/linux/swab.h:102:54: note: in definition of macro '__swab16' > > > > 102 | #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x)) > > > > | ^ > > > > ../include/linux/byteorder/generic.h:97:21: note: in expansion of macro '__be16_to_cpu' > > > > 97 | #define be16_to_cpu __be16_to_cpu > > > > | ^~~~~~~~~~~~~ > > > > ../kernel/bpf/lpm_trie.c:206:28: note: in expansion of macro 'be16_to_cpu' > > > > 206 | u16 diff = be16_to_cpu(*(__be16 *)&node->data[i] > > > > ^ > > > > | ^~~~~~~~~~~ > > > > In file included from ../include/linux/bpf.h:7: > > > > ../include/uapi/linux/bpf.h:82:17: note: while referencing 'data' > > > > 82 | __u8 data[0]; /* Arbitrary size */ > > > > | ^~~~ > > > > > > > > And found at run-time under CONFIG_FORTIFY_SOURCE: > > > > > > > > UBSAN: array-index-out-of-bounds in kernel/bpf/lpm_trie.c:218:49 > > > > index 0 is out of range for type '__u8 [*]' > > > > > > > > This includes fixing the selftest which was incorrectly using a > > > > variable length struct as a header, identified earlier[1]. Avoid this > > > > by just explicitly including the prefixlen member instead of struct > > > > bpf_lpm_trie_key. > > > > > > > > Note that it is not possible to simply remove the "data" member, as it > > > > is referenced by userspace > > > > > > > > cilium: > > > > struct egress_gw_policy_key in_key = { > > > > .lpm_key = { 32 + 24, {} }, > > > > .saddr = CLIENT_IP, > > > > .daddr = EXTERNAL_SVC_IP & 0Xffffff, > > > > }; > > > > > > > > systemd: > > > > ipv6_map_fd = bpf_map_new( > > > > BPF_MAP_TYPE_LPM_TRIE, > > > > offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t)*4, > > > > sizeof(uint64_t), > > > > ... > > > > > > > > The only risk to UAPI would be if sizeof() were used directly on the > > > > data member, which it does not seem to be. It is only used as a static > > > > initializer destination and to find its location via offsetof(). > > > > > > > > Link: https://lore.kernel.org/all/202206281009.4332AA33@keescook/ [1] > > > > Reported-by: Mark Rutland <mark.rutland@arm.com> > > > > Closes: https://paste.debian.net/hidden/ca500597/ > > > > > > mmh... this URL expires: 2024-05-15 > > > > Yup, but that's why I included the run-time splat above too. :) > > I don't quite follow, this basically undoes 3024d95a4c52 ("bpf: Partially revert > flexible-array member replacement") again with the small change that this 'fixes' > up the BPF selftest to not embed struct bpf_lpm_trie_key. > > Outside of BPF selftests though aren't we readding the same error that we fixed > earlier for BPF programs in the wild which embed struct bpf_lpm_trie_key into their > key structure? Oops, yes, sorry. I see how that cilium does include it in the same fashion. I will adjust this patch again. Thanks for double-checking! struct egress_gw_policy_key { struct bpf_lpm_trie_key lpm_key; __u32 saddr; __u32 daddr; };
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 754e68ca8744..359dd8a429c1 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -80,7 +80,7 @@ struct bpf_insn { /* Key of an a BPF_MAP_TYPE_LPM_TRIE entry */ struct bpf_lpm_trie_key { __u32 prefixlen; /* up to 32 for AF_INET, 128 for AF_INET6 */ - __u8 data[0]; /* Arbitrary size */ + __u8 data[]; /* Arbitrary size */ }; struct bpf_cgroup_storage_key { diff --git a/tools/testing/selftests/bpf/progs/map_ptr_kern.c b/tools/testing/selftests/bpf/progs/map_ptr_kern.c index 3325da17ec81..1d476c6ae284 100644 --- a/tools/testing/selftests/bpf/progs/map_ptr_kern.c +++ b/tools/testing/selftests/bpf/progs/map_ptr_kern.c @@ -316,7 +316,7 @@ struct lpm_trie { } __attribute__((preserve_access_index)); struct lpm_key { - struct bpf_lpm_trie_key trie_key; + __u32 prefixlen; __u32 data; };
Replace deprecated 0-length array in struct bpf_lpm_trie_key with flexible array. Found with GCC 13: ../kernel/bpf/lpm_trie.c:207:51: warning: array subscript i is outside array bounds of 'const __u8[0]' {aka 'const unsigned char[]'} [-Warray-bounds=] 207 | *(__be16 *)&key->data[i]); | ^~~~~~~~~~~~~ ../include/uapi/linux/swab.h:102:54: note: in definition of macro '__swab16' 102 | #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x)) | ^ ../include/linux/byteorder/generic.h:97:21: note: in expansion of macro '__be16_to_cpu' 97 | #define be16_to_cpu __be16_to_cpu | ^~~~~~~~~~~~~ ../kernel/bpf/lpm_trie.c:206:28: note: in expansion of macro 'be16_to_cpu' 206 | u16 diff = be16_to_cpu(*(__be16 *)&node->data[i] ^ | ^~~~~~~~~~~ In file included from ../include/linux/bpf.h:7: ../include/uapi/linux/bpf.h:82:17: note: while referencing 'data' 82 | __u8 data[0]; /* Arbitrary size */ | ^~~~ And found at run-time under CONFIG_FORTIFY_SOURCE: UBSAN: array-index-out-of-bounds in kernel/bpf/lpm_trie.c:218:49 index 0 is out of range for type '__u8 [*]' This includes fixing the selftest which was incorrectly using a variable length struct as a header, identified earlier[1]. Avoid this by just explicitly including the prefixlen member instead of struct bpf_lpm_trie_key. Note that it is not possible to simply remove the "data" member, as it is referenced by userspace cilium: struct egress_gw_policy_key in_key = { .lpm_key = { 32 + 24, {} }, .saddr = CLIENT_IP, .daddr = EXTERNAL_SVC_IP & 0Xffffff, }; systemd: ipv6_map_fd = bpf_map_new( BPF_MAP_TYPE_LPM_TRIE, offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t)*4, sizeof(uint64_t), ... The only risk to UAPI would be if sizeof() were used directly on the data member, which it does not seem to be. It is only used as a static initializer destination and to find its location via offsetof(). Link: https://lore.kernel.org/all/202206281009.4332AA33@keescook/ [1] Reported-by: Mark Rutland <mark.rutland@arm.com> Closes: https://paste.debian.net/hidden/ca500597/ Signed-off-by: Kees Cook <keescook@chromium.org> --- Cc: Alexei Starovoitov <ast@kernel.org> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Andrii Nakryiko <andrii@kernel.org> Cc: Martin KaFai Lau <martin.lau@linux.dev> Cc: Song Liu <song@kernel.org> Cc: Yonghong Song <yhs@fb.com> Cc: John Fastabend <john.fastabend@gmail.com> Cc: KP Singh <kpsingh@kernel.org> Cc: Stanislav Fomichev <sdf@google.com> Cc: Hao Luo <haoluo@google.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Mykola Lysenko <mykolal@fb.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Haowen Bai <baihaowen@meizu.com> Cc: bpf@vger.kernel.org Cc: linux-kselftest@vger.kernel.org v2- clarify commit log, add more failure examples v1- https://lore.kernel.org/all/63e531e3.170a0220.3a46a.3262@mx.google.com/ --- include/uapi/linux/bpf.h | 2 +- tools/testing/selftests/bpf/progs/map_ptr_kern.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)