libbpf: Fix use-after-free in btf_dump_name_dups

[ Upstream commit 93c660c ]

ASAN reports an use-after-free in btf_dump_name_dups:

ERROR: AddressSanitizer: heap-use-after-free on address 0xffff927006db at pc 0xaaaab5dfb618 bp 0xffffdd89b890 sp 0xffffdd89b928
READ of size 2 at 0xffff927006db thread T0
    #0 0xaaaab5dfb614 in __interceptor_strcmp.part.0 (test_progs+0x21b614)
    thesofproject#1 0xaaaab635f144 in str_equal_fn tools/lib/bpf/btf_dump.c:127
    thesofproject#2 0xaaaab635e3e0 in hashmap_find_entry tools/lib/bpf/hashmap.c:143
    thesofproject#3 0xaaaab635e72c in hashmap__find tools/lib/bpf/hashmap.c:212
    thesofproject#4 0xaaaab6362258 in btf_dump_name_dups tools/lib/bpf/btf_dump.c:1525
    thesofproject#5 0xaaaab636240c in btf_dump_resolve_name tools/lib/bpf/btf_dump.c:1552
    thesofproject#6 0xaaaab6362598 in btf_dump_type_name tools/lib/bpf/btf_dump.c:1567
    thesofproject#7 0xaaaab6360b48 in btf_dump_emit_struct_def tools/lib/bpf/btf_dump.c:912
    thesofproject#8 0xaaaab6360630 in btf_dump_emit_type tools/lib/bpf/btf_dump.c:798
    thesofproject#9 0xaaaab635f720 in btf_dump__dump_type tools/lib/bpf/btf_dump.c:282
    thesofproject#10 0xaaaab608523c in test_btf_dump_incremental tools/testing/selftests/bpf/prog_tests/btf_dump.c:236
    thesofproject#11 0xaaaab6097530 in test_btf_dump tools/testing/selftests/bpf/prog_tests/btf_dump.c:875
    thesofproject#12 0xaaaab6314ed0 in run_one_test tools/testing/selftests/bpf/test_progs.c:1062
    thesofproject#13 0xaaaab631a0a8 in main tools/testing/selftests/bpf/test_progs.c:1697
    thesofproject#14 0xffff9676d214 in __libc_start_main ../csu/libc-start.c:308
    thesofproject#15 0xaaaab5d65990  (test_progs+0x185990)

0xffff927006db is located 11 bytes inside of 16-byte region [0xffff927006d0,0xffff927006e0)
freed by thread T0 here:
    #0 0xaaaab5e2c7c4 in realloc (test_progs+0x24c7c4)
    thesofproject#1 0xaaaab634f4a0 in libbpf_reallocarray tools/lib/bpf/libbpf_internal.h:191
    thesofproject#2 0xaaaab634f840 in libbpf_add_mem tools/lib/bpf/btf.c:163
    thesofproject#3 0xaaaab636643c in strset_add_str_mem tools/lib/bpf/strset.c:106
    thesofproject#4 0xaaaab6366560 in strset__add_str tools/lib/bpf/strset.c:157
    thesofproject#5 0xaaaab6352d70 in btf__add_str tools/lib/bpf/btf.c:1519
    thesofproject#6 0xaaaab6353e10 in btf__add_field tools/lib/bpf/btf.c:2032
    thesofproject#7 0xaaaab6084fcc in test_btf_dump_incremental tools/testing/selftests/bpf/prog_tests/btf_dump.c:232
    thesofproject#8 0xaaaab6097530 in test_btf_dump tools/testing/selftests/bpf/prog_tests/btf_dump.c:875
    thesofproject#9 0xaaaab6314ed0 in run_one_test tools/testing/selftests/bpf/test_progs.c:1062
    thesofproject#10 0xaaaab631a0a8 in main tools/testing/selftests/bpf/test_progs.c:1697
    thesofproject#11 0xffff9676d214 in __libc_start_main ../csu/libc-start.c:308
    thesofproject#12 0xaaaab5d65990  (test_progs+0x185990)

previously allocated by thread T0 here:
    #0 0xaaaab5e2c7c4 in realloc (test_progs+0x24c7c4)
    thesofproject#1 0xaaaab634f4a0 in libbpf_reallocarray tools/lib/bpf/libbpf_internal.h:191
    thesofproject#2 0xaaaab634f840 in libbpf_add_mem tools/lib/bpf/btf.c:163
    thesofproject#3 0xaaaab636643c in strset_add_str_mem tools/lib/bpf/strset.c:106
    thesofproject#4 0xaaaab6366560 in strset__add_str tools/lib/bpf/strset.c:157
    thesofproject#5 0xaaaab6352d70 in btf__add_str tools/lib/bpf/btf.c:1519
    thesofproject#6 0xaaaab6353ff0 in btf_add_enum_common tools/lib/bpf/btf.c:2070
    thesofproject#7 0xaaaab6354080 in btf__add_enum tools/lib/bpf/btf.c:2102
    thesofproject#8 0xaaaab6082f50 in test_btf_dump_incremental tools/testing/selftests/bpf/prog_tests/btf_dump.c:162
    thesofproject#9 0xaaaab6097530 in test_btf_dump tools/testing/selftests/bpf/prog_tests/btf_dump.c:875
    thesofproject#10 0xaaaab6314ed0 in run_one_test tools/testing/selftests/bpf/test_progs.c:1062
    thesofproject#11 0xaaaab631a0a8 in main tools/testing/selftests/bpf/test_progs.c:1697
    thesofproject#12 0xffff9676d214 in __libc_start_main ../csu/libc-start.c:308
    thesofproject#13 0xaaaab5d65990  (test_progs+0x185990)

The reason is that the key stored in hash table name_map is a string
address, and the string memory is allocated by realloc() function, when
the memory is resized by realloc() later, the old memory may be freed,
so the address stored in name_map references to a freed memory, causing
use-after-free.

Fix it by storing duplicated string address in name_map.

Fixes: 919d2b1 ("libbpf: Allow modification of BTF and add btf__add_str API")
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/bpf/20221011120108.782373-2-xukuohai@huaweicloud.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

tools/lib/bpf/btf_dump.c

@@ -188,6 +188,17 @@ static int btf_dump_resize(struct btf_dump *d)
 	return 0;
 }
 
+static void btf_dump_free_names(struct hashmap *map)
+{
+	size_t bkt;
+	struct hashmap_entry *cur;
+
+	hashmap__for_each_entry(map, cur, bkt)
+		free((void *)cur->key);
+
+	hashmap__free(map);
+}
+
 void btf_dump__free(struct btf_dump *d)
 {
 	int i;
@@ -206,8 +217,8 @@ void btf_dump__free(struct btf_dump *d)
 	free(d->cached_names);
 	free(d->emit_queue);
 	free(d->decl_stack);
-	hashmap__free(d->type_names);
-	hashmap__free(d->ident_names);
+	btf_dump_free_names(d->type_names);
+	btf_dump_free_names(d->ident_names);
 
 	free(d);
 }
@@ -1392,11 +1403,23 @@ static void btf_dump_emit_type_chain(struct btf_dump *d,
 static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
 				 const char *orig_name)
 {
+	char *old_name, *new_name;
 	size_t dup_cnt = 0;
+	int err;
+
+	new_name = strdup(orig_name);
+	if (!new_name)
+		return 1;
 
 	hashmap__find(name_map, orig_name, (void **)&dup_cnt);
 	dup_cnt++;
-	hashmap__set(name_map, orig_name, (void *)dup_cnt, NULL, NULL);
+
+	err = hashmap__set(name_map, new_name, (void *)dup_cnt,
+			   (const void **)&old_name, NULL);
+	if (err)
+		free(new_name);
+
+	free(old_name);
 
 	return dup_cnt;
 }