| Message ID | 20240220185421.it.949-kees@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v4] bpf: Replace bpf_lpm_trie_key 0-length array with flexible array | expand |
On 2/20/24 7:54 PM, 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 [*]' > > Changing struct bpf_lpm_trie_key is difficult since has been used by > userspace. For example, in Cilium: > > struct egress_gw_policy_key { > struct bpf_lpm_trie_key lpm_key; > __u32 saddr; > __u32 daddr; > }; > > While direct references to the "data" member haven't been found, there > are static initializers what include the final member. For example, > the "{}" here: > > struct egress_gw_policy_key in_key = { > .lpm_key = { 32 + 24, {} }, > .saddr = CLIENT_IP, > .daddr = EXTERNAL_SVC_IP & 0Xffffff, > }; > > To avoid the build time and run time warnings seen with a 0-sized > trailing array for struct bpf_lpm_trie_key, introduce a new struct > that correctly uses a flexible array for the trailing bytes, > struct bpf_lpm_trie_key_u8. As part of this, include the "header" > portion (which is just the "prefixlen" member), so it can be used > by anything building a bpf_lpr_trie_key that has trailing members that > aren't a u8 flexible array (like the self-test[1]), which is named > struct bpf_lpm_trie_key_hdr. > > Adjust the kernel code to use struct bpf_lpm_trie_key_u8 through-out, > and for the selftest to use struct bpf_lpm_trie_key_hdr. Add a comment > to the UAPI header directing folks to the two new options. > > 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/ > Acked-by: Gustavo A. R. Silva <gustavoars@kernel.org> > Signed-off-by: Kees Cook <keescook@chromium.org> [...] The build in BPF CI is still broken, did you try to build selftests? https://github.com/kernel-patches/bpf/actions/runs/7978647641 [...] GEN-SKEL [test_progs] linked_funcs.skel.h LINK-BPF [test_progs] test_usdt.bpf.o GEN-SKEL [test_progs-no_alu32] profiler1.skel.h GEN-SKEL [test_progs] test_usdt.skel.h In file included from /tmp/work/bpf/bpf/tools/include/uapi/linux/bpf.h:11, from test_cpp.cpp:4: /tmp/work/bpf/bpf/tools/include/uapi/linux/bpf.h:92:17: error: ‘struct bpf_lpm_trie_key_u8::<unnamed union>::bpf_lpm_trie_key_hdr’ invalid; an anonymous union may only have public non-static data members [-fpermissive] 92 | __struct_group(bpf_lpm_trie_key_hdr, hdr, /* no attrs */, | ^~~~~~~~~~~~~~~~~~~~ /tmp/work/bpf/bpf/tools/include/uapi/linux/stddef.h:29:10: note: in definition of macro ‘__struct_group’ 29 | struct TAG { MEMBERS } ATTRS NAME; \ | ^~~ BINARY bench make: *** [Makefile:703: /tmp/work/bpf/bpf/tools/testing/selftests/bpf/test_cpp] Error 1 make: *** Waiting for unfinished jobs.... make: Leaving directory '/tmp/work/bpf/bpf/tools/testing/selftests/bpf' Error: Process completed with exit code 2. > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index 754e68ca8744..31e9bdd4641e 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -8,6 +8,7 @@ > #ifndef _UAPI__LINUX_BPF_H__ > #define _UAPI__LINUX_BPF_H__ > > +#include <linux/stddef.h> > #include <linux/types.h> > #include <linux/bpf_common.h> > > @@ -77,12 +78,24 @@ struct bpf_insn { > __s32 imm; /* signed immediate constant */ > }; > > -/* Key of an a BPF_MAP_TYPE_LPM_TRIE entry */ > +/* Deprecated: use struct bpf_lpm_trie_key_u8 (when the "data" member is needed for > + * byte access) or struct bpf_lpm_trie_key_hdr (when using an alternative type for > + * the trailing flexible array member) instead. > + */ > struct bpf_lpm_trie_key { > __u32 prefixlen; /* up to 32 for AF_INET, 128 for AF_INET6 */ > __u8 data[0]; /* Arbitrary size */ > }; > > +/* Key of an a BPF_MAP_TYPE_LPM_TRIE entry, with trailing byte array. */ > +struct bpf_lpm_trie_key_u8 { > + __struct_group(bpf_lpm_trie_key_hdr, hdr, /* no attrs */, > + /* up to 32 for AF_INET, 128 for AF_INET6 */ > + __u32 prefixlen; > + ); > + __u8 data[]; /* Arbitrary size */ > +}; > + > struct bpf_cgroup_storage_key { > __u64 cgroup_inode_id; /* cgroup inode id */ > __u32 attach_type; /* program attach type (enum bpf_attach_type) */
On Wed, Feb 21, 2024 at 05:39:55PM +0100, Daniel Borkmann wrote: > On 2/20/24 7:54 PM, 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 [*]' > > > > Changing struct bpf_lpm_trie_key is difficult since has been used by > > userspace. For example, in Cilium: > > > > struct egress_gw_policy_key { > > struct bpf_lpm_trie_key lpm_key; > > __u32 saddr; > > __u32 daddr; > > }; > > > > While direct references to the "data" member haven't been found, there > > are static initializers what include the final member. For example, > > the "{}" here: > > > > struct egress_gw_policy_key in_key = { > > .lpm_key = { 32 + 24, {} }, > > .saddr = CLIENT_IP, > > .daddr = EXTERNAL_SVC_IP & 0Xffffff, > > }; > > > > To avoid the build time and run time warnings seen with a 0-sized > > trailing array for struct bpf_lpm_trie_key, introduce a new struct > > that correctly uses a flexible array for the trailing bytes, > > struct bpf_lpm_trie_key_u8. As part of this, include the "header" > > portion (which is just the "prefixlen" member), so it can be used > > by anything building a bpf_lpr_trie_key that has trailing members that > > aren't a u8 flexible array (like the self-test[1]), which is named > > struct bpf_lpm_trie_key_hdr. > > > > Adjust the kernel code to use struct bpf_lpm_trie_key_u8 through-out, > > and for the selftest to use struct bpf_lpm_trie_key_hdr. Add a comment > > to the UAPI header directing folks to the two new options. > > > > 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/ > > Acked-by: Gustavo A. R. Silva <gustavoars@kernel.org> > > Signed-off-by: Kees Cook <keescook@chromium.org> > [...] > > The build in BPF CI is still broken, did you try to build selftests? I did! I didn't have this error. :( > https://github.com/kernel-patches/bpf/actions/runs/7978647641 Thanks for the pointer. It took a bit of digging, but I found this: https://github.com/libbpf/ci/blob/main/build-selftests/build_selftests.sh which is much more involved than just "make -C tools/testing/selftests/bpf" > > [...] > GEN-SKEL [test_progs] linked_funcs.skel.h > LINK-BPF [test_progs] test_usdt.bpf.o > GEN-SKEL [test_progs-no_alu32] profiler1.skel.h > GEN-SKEL [test_progs] test_usdt.skel.h > In file included from /tmp/work/bpf/bpf/tools/include/uapi/linux/bpf.h:11, > from test_cpp.cpp:4: > /tmp/work/bpf/bpf/tools/include/uapi/linux/bpf.h:92:17: error: ‘struct bpf_lpm_trie_key_u8::<unnamed union>::bpf_lpm_trie_key_hdr’ invalid; an anonymous union may only have public non-static data members [-fpermissive] > 92 | __struct_group(bpf_lpm_trie_key_hdr, hdr, /* no attrs */, > | ^~~~~~~~~~~~~~~~~~~~ > /tmp/work/bpf/bpf/tools/include/uapi/linux/stddef.h:29:10: note: in definition of macro ‘__struct_group’ > 29 | struct TAG { MEMBERS } ATTRS NAME; \ > | ^~~ I'll see if I can figure out where this is coming from. This sounds like something is being built with an unexpectedly strict option. (The above report seems weird -- this isn't coming from -fpermissive, and is actually an _error_ not a warning, which is the opposite of what -fpermissive is supposed to do.) Also the mention of "public" is scary here... that implies a C++ compiler is involved? Maybe that's why my builds didn't catch this? > make: *** [Makefile:703: /tmp/work/bpf/bpf/tools/testing/selftests/bpf/test_cpp] Error 1 Ah yes, cpp. Fun. I will try to reproduce this failure.
On Wed, Feb 21, 2024 at 05:39:55PM +0100, Daniel Borkmann wrote:
> The build in BPF CI is still broken, did you try to build selftests?
Okay, I give up. How is a mortal supposed to build these?
If I try to follow what I see in
https://github.com/libbpf/ci/blob/main/build-selftests/build_selftests.sh
I just get more and more kinds of errors:
In file included from progs/cb_refs.c:5:
progs/../bpf_testmod/bpf_testmod_kfunc.h:29:8: error: redefinition of 'prog_test_pass1'
29 | struct prog_test_pass1 {
| ^
/srv/code/tools/testing/selftests/bpf/tools/include/vmlinux.h:106850:8: note: previous definition is
here
106850 | struct prog_test_pass1 {
| ^
Messing around with deleting vmlinux.h seems to get me further, but later:
/srv/code/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c: In function 'bpf_testmod_ops_is_valid_access':
/srv/code/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c:535:16: error: implicit declaration of function 'bpf_tracing_btf_ctx_access' [-Werror=implicit-function-declaration]
535 | return bpf_tracing_btf_ctx_access(off, size, type, prog, info);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~
and then I'm stuck. It looks like the build isn't actually using
KBUILD_OUTPUT for finding includes. If I try to add -I flags to the
Makefile I just drown in new errors.
diff --git a/Documentation/bpf/map_lpm_trie.rst b/Documentation/bpf/map_lpm_trie.rst index 74d64a30f500..f9cd579496c9 100644 --- a/Documentation/bpf/map_lpm_trie.rst +++ b/Documentation/bpf/map_lpm_trie.rst @@ -17,7 +17,7 @@ significant byte. LPM tries may be created with a maximum prefix length that is a multiple of 8, in the range from 8 to 2048. The key used for lookup and update -operations is a ``struct bpf_lpm_trie_key``, extended by +operations is a ``struct bpf_lpm_trie_key_u8``, extended by ``max_prefixlen/8`` bytes. - For IPv4 addresses the data length is 4 bytes diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 754e68ca8744..31e9bdd4641e 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -8,6 +8,7 @@ #ifndef _UAPI__LINUX_BPF_H__ #define _UAPI__LINUX_BPF_H__ +#include <linux/stddef.h> #include <linux/types.h> #include <linux/bpf_common.h> @@ -77,12 +78,24 @@ struct bpf_insn { __s32 imm; /* signed immediate constant */ }; -/* Key of an a BPF_MAP_TYPE_LPM_TRIE entry */ +/* Deprecated: use struct bpf_lpm_trie_key_u8 (when the "data" member is needed for + * byte access) or struct bpf_lpm_trie_key_hdr (when using an alternative type for + * the trailing flexible array member) instead. + */ struct bpf_lpm_trie_key { __u32 prefixlen; /* up to 32 for AF_INET, 128 for AF_INET6 */ __u8 data[0]; /* Arbitrary size */ }; +/* Key of an a BPF_MAP_TYPE_LPM_TRIE entry, with trailing byte array. */ +struct bpf_lpm_trie_key_u8 { + __struct_group(bpf_lpm_trie_key_hdr, hdr, /* no attrs */, + /* up to 32 for AF_INET, 128 for AF_INET6 */ + __u32 prefixlen; + ); + __u8 data[]; /* Arbitrary size */ +}; + struct bpf_cgroup_storage_key { __u64 cgroup_inode_id; /* cgroup inode id */ __u32 attach_type; /* program attach type (enum bpf_attach_type) */ diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c index b32be680da6c..050fe1ebf0f7 100644 --- a/kernel/bpf/lpm_trie.c +++ b/kernel/bpf/lpm_trie.c @@ -164,13 +164,13 @@ static inline int extract_bit(const u8 *data, size_t index) */ static size_t longest_prefix_match(const struct lpm_trie *trie, const struct lpm_trie_node *node, - const struct bpf_lpm_trie_key *key) + const struct bpf_lpm_trie_key_u8 *key) { u32 limit = min(node->prefixlen, key->prefixlen); u32 prefixlen = 0, i = 0; BUILD_BUG_ON(offsetof(struct lpm_trie_node, data) % sizeof(u32)); - BUILD_BUG_ON(offsetof(struct bpf_lpm_trie_key, data) % sizeof(u32)); + BUILD_BUG_ON(offsetof(struct bpf_lpm_trie_key_u8, data) % sizeof(u32)); #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && defined(CONFIG_64BIT) @@ -229,7 +229,7 @@ static void *trie_lookup_elem(struct bpf_map *map, void *_key) { struct lpm_trie *trie = container_of(map, struct lpm_trie, map); struct lpm_trie_node *node, *found = NULL; - struct bpf_lpm_trie_key *key = _key; + struct bpf_lpm_trie_key_u8 *key = _key; if (key->prefixlen > trie->max_prefixlen) return NULL; @@ -309,7 +309,7 @@ static long trie_update_elem(struct bpf_map *map, struct lpm_trie *trie = container_of(map, struct lpm_trie, map); struct lpm_trie_node *node, *im_node = NULL, *new_node = NULL; struct lpm_trie_node __rcu **slot; - struct bpf_lpm_trie_key *key = _key; + struct bpf_lpm_trie_key_u8 *key = _key; unsigned long irq_flags; unsigned int next_bit; size_t matchlen = 0; @@ -437,7 +437,7 @@ static long trie_update_elem(struct bpf_map *map, static long trie_delete_elem(struct bpf_map *map, void *_key) { struct lpm_trie *trie = container_of(map, struct lpm_trie, map); - struct bpf_lpm_trie_key *key = _key; + struct bpf_lpm_trie_key_u8 *key = _key; struct lpm_trie_node __rcu **trim, **trim2; struct lpm_trie_node *node, *parent; unsigned long irq_flags; @@ -536,7 +536,7 @@ static long trie_delete_elem(struct bpf_map *map, void *_key) sizeof(struct lpm_trie_node)) #define LPM_VAL_SIZE_MIN 1 -#define LPM_KEY_SIZE(X) (sizeof(struct bpf_lpm_trie_key) + (X)) +#define LPM_KEY_SIZE(X) (sizeof(struct bpf_lpm_trie_key_u8) + (X)) #define LPM_KEY_SIZE_MAX LPM_KEY_SIZE(LPM_DATA_SIZE_MAX) #define LPM_KEY_SIZE_MIN LPM_KEY_SIZE(LPM_DATA_SIZE_MIN) @@ -565,7 +565,7 @@ static struct bpf_map *trie_alloc(union bpf_attr *attr) /* copy mandatory map attributes */ bpf_map_init_from_attr(&trie->map, attr); trie->data_size = attr->key_size - - offsetof(struct bpf_lpm_trie_key, data); + offsetof(struct bpf_lpm_trie_key_u8, data); trie->max_prefixlen = trie->data_size * 8; spin_lock_init(&trie->lock); @@ -616,7 +616,7 @@ static int trie_get_next_key(struct bpf_map *map, void *_key, void *_next_key) { struct lpm_trie_node *node, *next_node = NULL, *parent, *search_root; struct lpm_trie *trie = container_of(map, struct lpm_trie, map); - struct bpf_lpm_trie_key *key = _key, *next_key = _next_key; + struct bpf_lpm_trie_key_u8 *key = _key, *next_key = _next_key; struct lpm_trie_node **node_stack = NULL; int err = 0, stack_ptr = -1; unsigned int next_bit; @@ -703,7 +703,7 @@ static int trie_get_next_key(struct bpf_map *map, void *_key, void *_next_key) } do_copy: next_key->prefixlen = next_node->prefixlen; - memcpy((void *)next_key + offsetof(struct bpf_lpm_trie_key, data), + memcpy((void *)next_key + offsetof(struct bpf_lpm_trie_key_u8, data), next_node->data, trie->data_size); free_stack: kfree(node_stack); @@ -715,7 +715,7 @@ static int trie_check_btf(const struct bpf_map *map, const struct btf_type *key_type, const struct btf_type *value_type) { - /* Keys must have struct bpf_lpm_trie_key embedded. */ + /* Keys must have struct bpf_lpm_trie_key_u8 embedded. */ return BTF_INFO_KIND(key_type->info) != BTF_KIND_STRUCT ? -EINVAL : 0; } diff --git a/samples/bpf/map_perf_test_user.c b/samples/bpf/map_perf_test_user.c index d2fbcf963cdf..07ff471ed6ae 100644 --- a/samples/bpf/map_perf_test_user.c +++ b/samples/bpf/map_perf_test_user.c @@ -370,7 +370,7 @@ static void run_perf_test(int tasks) static void fill_lpm_trie(void) { - struct bpf_lpm_trie_key *key; + struct bpf_lpm_trie_key_u8 *key; unsigned long value = 0; unsigned int i; int r; diff --git a/samples/bpf/xdp_router_ipv4_user.c b/samples/bpf/xdp_router_ipv4_user.c index 9d41db09c480..266fdd0b025d 100644 --- a/samples/bpf/xdp_router_ipv4_user.c +++ b/samples/bpf/xdp_router_ipv4_user.c @@ -91,7 +91,7 @@ static int recv_msg(struct sockaddr_nl sock_addr, int sock) static void read_route(struct nlmsghdr *nh, int nll) { char dsts[24], gws[24], ifs[16], dsts_len[24], metrics[24]; - struct bpf_lpm_trie_key *prefix_key; + struct bpf_lpm_trie_key_u8 *prefix_key; struct rtattr *rt_attr; struct rtmsg *rt_msg; int rtm_family; diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 7f24d898efbb..76b1b41c0dce 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -8,6 +8,7 @@ #ifndef _UAPI__LINUX_BPF_H__ #define _UAPI__LINUX_BPF_H__ +#include <linux/stddef.h> #include <linux/types.h> #include <linux/bpf_common.h> @@ -77,12 +78,24 @@ struct bpf_insn { __s32 imm; /* signed immediate constant */ }; -/* Key of an a BPF_MAP_TYPE_LPM_TRIE entry */ +/* Deprecated: use struct bpf_lpm_trie_key_u8 (when the "data" member is needed for + * byte access) or struct bpf_lpm_trie_key_hdr (when using an alternative type for + * the trailing flexible array member) instead. + */ struct bpf_lpm_trie_key { __u32 prefixlen; /* up to 32 for AF_INET, 128 for AF_INET6 */ __u8 data[0]; /* Arbitrary size */ }; +/* Key of an a BPF_MAP_TYPE_LPM_TRIE entry, with trailing byte array. */ +struct bpf_lpm_trie_key_u8 { + __struct_group(bpf_lpm_trie_key_hdr, hdr, /* no attrs */, + /* up to 32 for AF_INET, 128 for AF_INET6 */ + __u32 prefixlen; + ); + __u8 data[]; /* Arbitrary size */ +}; + struct bpf_cgroup_storage_key { __u64 cgroup_inode_id; /* cgroup inode id */ __u32 attach_type; /* program attach type (enum bpf_attach_type) */ diff --git a/tools/testing/selftests/bpf/progs/map_ptr_kern.c b/tools/testing/selftests/bpf/progs/map_ptr_kern.c index 3325da17ec81..efaf622c28dd 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; + struct bpf_lpm_trie_key_hdr trie_key; __u32 data; }; diff --git a/tools/testing/selftests/bpf/test_lpm_map.c b/tools/testing/selftests/bpf/test_lpm_map.c index c028d621c744..d98c72dc563e 100644 --- a/tools/testing/selftests/bpf/test_lpm_map.c +++ b/tools/testing/selftests/bpf/test_lpm_map.c @@ -211,7 +211,7 @@ static void test_lpm_map(int keysize) volatile size_t n_matches, n_matches_after_delete; size_t i, j, n_nodes, n_lookups; struct tlpm_node *t, *list = NULL; - struct bpf_lpm_trie_key *key; + struct bpf_lpm_trie_key_u8 *key; uint8_t *data, *value; int r, map; @@ -331,8 +331,8 @@ static void test_lpm_map(int keysize) static void test_lpm_ipaddr(void) { LIBBPF_OPTS(bpf_map_create_opts, opts, .map_flags = BPF_F_NO_PREALLOC); - struct bpf_lpm_trie_key *key_ipv4; - struct bpf_lpm_trie_key *key_ipv6; + struct bpf_lpm_trie_key_u8 *key_ipv4; + struct bpf_lpm_trie_key_u8 *key_ipv6; size_t key_size_ipv4; size_t key_size_ipv6; int map_fd_ipv4; @@ -423,7 +423,7 @@ static void test_lpm_ipaddr(void) static void test_lpm_delete(void) { LIBBPF_OPTS(bpf_map_create_opts, opts, .map_flags = BPF_F_NO_PREALLOC); - struct bpf_lpm_trie_key *key; + struct bpf_lpm_trie_key_u8 *key; size_t key_size; int map_fd; __u64 value; @@ -532,7 +532,7 @@ static void test_lpm_delete(void) static void test_lpm_get_next_key(void) { LIBBPF_OPTS(bpf_map_create_opts, opts, .map_flags = BPF_F_NO_PREALLOC); - struct bpf_lpm_trie_key *key_p, *next_key_p; + struct bpf_lpm_trie_key_u8 *key_p, *next_key_p; size_t key_size; __u32 value = 0; int map_fd; @@ -693,9 +693,9 @@ static void *lpm_test_command(void *arg) { int i, j, ret, iter, key_size; struct lpm_mt_test_info *info = arg; - struct bpf_lpm_trie_key *key_p; + struct bpf_lpm_trie_key_u8 *key_p; - key_size = sizeof(struct bpf_lpm_trie_key) + sizeof(__u32); + key_size = sizeof(*key_p) + sizeof(__u32); key_p = alloca(key_size); for (iter = 0; iter < info->iter; iter++) for (i = 0; i < MAX_TEST_KEYS; i++) { @@ -717,7 +717,7 @@ static void *lpm_test_command(void *arg) ret = bpf_map_lookup_elem(info->map_fd, key_p, &value); assert(ret == 0 || errno == ENOENT); } else { - struct bpf_lpm_trie_key *next_key_p = alloca(key_size); + struct bpf_lpm_trie_key_u8 *next_key_p = alloca(key_size); ret = bpf_map_get_next_key(info->map_fd, key_p, next_key_p); assert(ret == 0 || errno == ENOENT || errno == ENOMEM); } @@ -752,7 +752,7 @@ static void test_lpm_multi_thread(void) /* create a trie */ value_size = sizeof(__u32); - key_size = sizeof(struct bpf_lpm_trie_key) + value_size; + key_size = sizeof(struct bpf_lpm_trie_key_hdr) + value_size; map_fd = bpf_map_create(BPF_MAP_TYPE_LPM_TRIE, NULL, key_size, value_size, 100, &opts); /* create 4 threads to test update, delete, lookup and get_next_key */
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 [*]' Changing struct bpf_lpm_trie_key is difficult since has been used by userspace. For example, in Cilium: struct egress_gw_policy_key { struct bpf_lpm_trie_key lpm_key; __u32 saddr; __u32 daddr; }; While direct references to the "data" member haven't been found, there are static initializers what include the final member. For example, the "{}" here: struct egress_gw_policy_key in_key = { .lpm_key = { 32 + 24, {} }, .saddr = CLIENT_IP, .daddr = EXTERNAL_SVC_IP & 0Xffffff, }; To avoid the build time and run time warnings seen with a 0-sized trailing array for struct bpf_lpm_trie_key, introduce a new struct that correctly uses a flexible array for the trailing bytes, struct bpf_lpm_trie_key_u8. As part of this, include the "header" portion (which is just the "prefixlen" member), so it can be used by anything building a bpf_lpr_trie_key that has trailing members that aren't a u8 flexible array (like the self-test[1]), which is named struct bpf_lpm_trie_key_hdr. Adjust the kernel code to use struct bpf_lpm_trie_key_u8 through-out, and for the selftest to use struct bpf_lpm_trie_key_hdr. Add a comment to the UAPI header directing folks to the two new options. 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/ Acked-by: Gustavo A. R. Silva <gustavoars@kernel.org> Signed-off-by: Kees Cook <keescook@chromium.org> --- Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Alexei Starovoitov <ast@kernel.org> 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 v4- add missing stddef.h include v3- https://lore.kernel.org/all/20240219234121.make.373-kees@kernel.org/ v2- https://lore.kernel.org/lkml/20240216235536.it.234-kees@kernel.org/ v1- https://lore.kernel.org/lkml/20230204183241.never.481-kees@kernel.org/ --- Documentation/bpf/map_lpm_trie.rst | 2 +- include/uapi/linux/bpf.h | 15 +++++++++++++- kernel/bpf/lpm_trie.c | 20 +++++++++---------- samples/bpf/map_perf_test_user.c | 2 +- samples/bpf/xdp_router_ipv4_user.c | 2 +- tools/include/uapi/linux/bpf.h | 15 +++++++++++++- .../selftests/bpf/progs/map_ptr_kern.c | 2 +- tools/testing/selftests/bpf/test_lpm_map.c | 18 ++++++++--------- 8 files changed, 51 insertions(+), 25 deletions(-)