[PATCH bpf-next 1/5] bpf: Check tail zero of bpf_common_attr using offsetofend

[Leon Hwang <leon.hwang@linux.dev>]

Because of the 8-byte alignment, the compiler will pad struct
bpf_common_attr to 24 bytes. That said, sizeof(attr_common) is 24 instead
of 20.

When check tail zero using sizeof(attr_common) in
bpf_check_uarg_tail_zero(), there will be 4 bytes that won't be checked.

To also check the padding 4 bytes, replace sizeof(attr_common) with
offsetofend(struct bpf_common_attr, log_true_size).

Fixes: f28771c0691b ("bpf: Extend BPF syscall with common attributes support")
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 kernel/bpf/syscall.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 6600e126fbfb..83de8fb9b9aa 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -6278,7 +6278,9 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
 
 	memset(&attr_common, 0, sizeof(attr_common));
 	if (cmd & BPF_COMMON_ATTRS) {
-		err = bpf_check_uarg_tail_zero(uattr_common, sizeof(attr_common), size_common);
+		err = bpf_check_uarg_tail_zero(uattr_common,
+					       offsetofend(struct bpf_common_attr, log_true_size),
+					       size_common);
 		if (err)
 			return err;
 
-- 
2.54.0