[PATCH bpf-next v2 2/3] bpf/verifier: Use kmalloc_size_roundup() to match ksize() usage

[Kees Cook]

Round up allocations with kmalloc_size_roundup() so that the verifier's
use of ksize() is always accurate and no special handling of the memory
is needed by KASAN, UBSAN_BOUNDS, nor FORTIFY_SOURCE. Pass the new size
information back up to callers so they can use the space immediately,
so array resizing to happen less frequently as well.

Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: John Fastabend <john.fastabend@xxxxxxxxx>
Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
Cc: Martin KaFai Lau <martin.lau@xxxxxxxxx>
Cc: Song Liu <song@xxxxxxxxxx>
Cc: Yonghong Song <yhs@xxxxxx>
Cc: KP Singh <kpsingh@xxxxxxxxxx>
Cc: Stanislav Fomichev <sdf@xxxxxxxxxx>
Cc: Hao Luo <haoluo@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: bpf@xxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 kernel/bpf/verifier.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index eb8c34db74c7..1c040d27b8f6 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1008,9 +1008,9 @@ static void *copy_array(void *dst, const void *src, size_t n, size_t size, gfp_t
 	if (unlikely(check_mul_overflow(n, size, &bytes)))
 		return NULL;
 
-	if (ksize(dst) < bytes) {
+	if (ksize(dst) < ksize(src)) {
 		kfree(dst);
-		dst = kmalloc_track_caller(bytes, flags);
+		dst = kmalloc_track_caller(kmalloc_size_roundup(bytes), flags);
 		if (!dst)
 			return NULL;
 	}
@@ -1027,12 +1027,14 @@ static void *copy_array(void *dst, const void *src, size_t n, size_t size, gfp_t
  */
 static void *realloc_array(void *arr, size_t old_n, size_t new_n, size_t size)
 {
+	size_t alloc_size;
 	void *new_arr;
 
 	if (!new_n || old_n == new_n)
 		goto out;
 
-	new_arr = krealloc_array(arr, new_n, size, GFP_KERNEL);
+	alloc_size = kmalloc_size_roundup(size_mul(new_n, size));
+	new_arr = krealloc(arr, alloc_size, GFP_KERNEL);
 	if (!new_arr) {
 		kfree(arr);
 		return NULL;
@@ -2504,9 +2506,11 @@ static int push_jmp_history(struct bpf_verifier_env *env,
 {
 	u32 cnt = cur->jmp_history_cnt;
 	struct bpf_idx_pair *p;
+	size_t alloc_size;
 
 	cnt++;
-	p = krealloc(cur->jmp_history, cnt * sizeof(*p), GFP_USER);
+	alloc_size = kmalloc_size_roundup(size_mul(cnt, sizeof(*p)));
+	p = krealloc(cur->jmp_history, alloc_size, GFP_USER);
 	if (!p)
 		return -ENOMEM;
 	p[cnt - 1].idx = env->insn_idx;
-- 
2.34.1