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selftests/bpf: Fix task_local_data data allocation size

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Currently, when allocating memory for data, size of tld_data_u->start
is not taken into account. This may cause OOB access. Fixed it by adding
the non-flexible array part of tld_data_u.

Besides, explicitly align tld_data_u->data to 8 bytes in case some
fields are added before data in the future. It could break the
assumption that every data field is 8 byte aligned and
sizeof(tld_data_u) will no longer be equal to
offsetof(struct tld_data_u, data), which we use interchangeably.

Signed-off-by: Amery Hung <ameryhung@gmail.com>
Acked-by: Sun Jian <sun.jian.kdev@gmail.com>
Link: https://lore.kernel.org/r/20260331213555.1993883-2-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Amery Hung 2026-03-31 14:35:51 -07:00 committed by Alexei Starovoitov
parent e8aec1058c
commit 7c8ca532a7
2 changed files with 8 additions and 6 deletions
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12
tools/testing/selftests/bpf/prog_tests/task_local_data.h
View File

@ -90,7 +90,7 @@ typedef struct {
struct tld_metadata {
char name[TLD_NAME_LEN];
_Atomic __u16 size;
_Atomic __u16 size; /* size of tld_data_u->data */
};
struct tld_meta_u {
@ -101,7 +101,7 @@ struct tld_meta_u {
struct tld_data_u {
__u64 start; /* offset of tld_data_u->data in a page */
char data[];
char data[] __attribute__((aligned(8)));
};
struct tld_map_value {
@ -158,6 +158,7 @@ static int __tld_init_data_p(int map_fd)
struct tld_data_u *data;
void *data_alloc = NULL;
int err, tid_fd = -1;
size_t size;
tid_fd = syscall(SYS_pidfd_open, sys_gettid(), O_EXCL);
if (tid_fd < 0) {
@ -173,9 +174,10 @@ static int __tld_init_data_p(int map_fd)
* tld_meta_p->size = TLD_DYN_DATA_SIZE +
* total size of TLDs defined via TLD_DEFINE_KEY()
*/
data_alloc = (use_aligned_alloc || tld_meta_p->size * 2 >= TLD_PAGE_SIZE) ?
aligned_alloc(TLD_PAGE_SIZE, tld_meta_p->size) :
malloc(tld_meta_p->size * 2);
size = tld_meta_p->size + sizeof(struct tld_data_u);
data_alloc = (use_aligned_alloc || size * 2 >= TLD_PAGE_SIZE) ?
aligned_alloc(TLD_PAGE_SIZE, size) :
malloc(size * 2);
if (!data_alloc) {
err = -ENOMEM;
goto out;

2
tools/testing/selftests/bpf/progs/task_local_data.bpf.h
View File

@ -87,7 +87,7 @@ struct tld_meta_u {
struct tld_data_u {
__u64 start; /* offset of tld_data_u->data in a page */
char data[__PAGE_SIZE - sizeof(__u64)];
char data[__PAGE_SIZE - sizeof(__u64)] __attribute__((aligned(8)));
};
struct tld_map_value {