bpf: Replace offsetof() with struct_size()

Compared to offsetof(), struct_size() provides additional compile-time
checks for structs with flexible arrays (e.g., __must_be_array()).

No functional changes intended.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250503151513.343931-2-thorsten.blum@linux.dev

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index a91822bae043baa02fe76479c50e82ba3a7ed6af..6b21ca67070c76ecc664367fd369fbe4f1d7b4bf 100644 (file)
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -26,6 +26,7 @@
 #include <linux/bsearch.h>
 #include <linux/kobject.h>
 #include <linux/sysfs.h>
+#include <linux/overflow.h>
 
 #include <net/netfilter/nf_bpf_link.h>
 
@@ -3957,7 +3958,7 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
        /* This needs to be kzalloc to zero out padding and unused fields, see
         * comment in btf_record_equal.
         */
-       rec = kzalloc(offsetof(struct btf_record, fields[cnt]), GFP_KERNEL | __GFP_NOWARN);
+       rec = kzalloc(struct_size(rec, fields, cnt), GFP_KERNEL | __GFP_NOWARN);
        if (!rec)
                return ERR_PTR(-ENOMEM);
 
@@ -5583,7 +5584,7 @@ btf_parse_struct_metas(struct bpf_verifier_log *log, struct btf *btf)
                if (id < 0)
                        continue;
 
-               new_aof = krealloc(aof, offsetof(struct btf_id_set, ids[aof->cnt + 1]),
+               new_aof = krealloc(aof, struct_size(new_aof, ids, aof->cnt + 1),
                                   GFP_KERNEL | __GFP_NOWARN);
                if (!new_aof) {
                        ret = -ENOMEM;
@@ -5610,7 +5611,7 @@ btf_parse_struct_metas(struct bpf_verifier_log *log, struct btf *btf)
                if (ret != BTF_FIELD_FOUND)
                        continue;
 
-               new_aof = krealloc(aof, offsetof(struct btf_id_set, ids[aof->cnt + 1]),
+               new_aof = krealloc(aof, struct_size(new_aof, ids, aof->cnt + 1),
                                   GFP_KERNEL | __GFP_NOWARN);
                if (!new_aof) {
                        ret = -ENOMEM;
@@ -5647,7 +5648,7 @@ btf_parse_struct_metas(struct bpf_verifier_log *log, struct btf *btf)
                continue;
        parse:
                tab_cnt = tab ? tab->cnt : 0;
-               new_tab = krealloc(tab, offsetof(struct btf_struct_metas, types[tab_cnt + 1]),
+               new_tab = krealloc(tab, struct_size(new_tab, types, tab_cnt + 1),
                                   GFP_KERNEL | __GFP_NOWARN);
                if (!new_tab) {
                        ret = -ENOMEM;
@@ -8559,7 +8560,7 @@ static int btf_populate_kfunc_set(struct btf *btf, enum btf_kfunc_hook hook,
 
        /* Grow set */
        set = krealloc(tab->sets[hook],
-                      offsetof(struct btf_id_set8, pairs[set_cnt + add_set->cnt]),
+                      struct_size(set, pairs, set_cnt + add_set->cnt),
                       GFP_KERNEL | __GFP_NOWARN);
        if (!set) {
                ret = -ENOMEM;
@@ -8845,7 +8846,7 @@ int register_btf_id_dtor_kfuncs(const struct btf_id_dtor_kfunc *dtors, u32 add_c
        }
 
        tab = krealloc(btf->dtor_kfunc_tab,
-                      offsetof(struct btf_id_dtor_kfunc_tab, dtors[tab_cnt + add_cnt]),
+                      struct_size(tab, dtors, tab_cnt + add_cnt),
                       GFP_KERNEL | __GFP_NOWARN);
        if (!tab) {
                ret = -ENOMEM;
@@ -9403,8 +9404,7 @@ btf_add_struct_ops(struct btf *btf, struct bpf_struct_ops *st_ops,
 
        tab = btf->struct_ops_tab;
        if (!tab) {
-               tab = kzalloc(offsetof(struct btf_struct_ops_tab, ops[4]),
-                             GFP_KERNEL);
+               tab = kzalloc(struct_size(tab, ops, 4), GFP_KERNEL);
                if (!tab)
                        return -ENOMEM;
                tab->capacity = 4;
@@ -9417,8 +9417,7 @@ btf_add_struct_ops(struct btf *btf, struct bpf_struct_ops *st_ops,
 
        if (tab->cnt == tab->capacity) {
                new_tab = krealloc(tab,
-                                  offsetof(struct btf_struct_ops_tab,
-                                           ops[tab->capacity * 2]),
+                                  struct_size(tab, ops, tab->capacity * 2),
                                   GFP_KERNEL);
                if (!new_tab)
                        return -ENOMEM;