6.11-stable review patch. If anyone has any objections, please let me know.
------------------
From: Hou Tao houtao1@huawei.com
[ Upstream commit 797d73ee232dd1833dec4824bc53a22032e97c1c ]
When trying to repeat the btf fields for array of nested struct, it doesn't check the remaining info_cnt. The following splat will be reported when the value of ret * nelems is greater than BTF_FIELDS_MAX:
------------[ cut here ]------------ UBSAN: array-index-out-of-bounds in ../kernel/bpf/btf.c:3951:49 index 11 is out of range for type 'btf_field_info [11]' CPU: 6 UID: 0 PID: 411 Comm: test_progs ...... 6.11.0-rc4+ #1 Tainted: [O]=OOT_MODULE Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ... Call Trace: <TASK> dump_stack_lvl+0x57/0x70 dump_stack+0x10/0x20 ubsan_epilogue+0x9/0x40 __ubsan_handle_out_of_bounds+0x6f/0x80 ? kallsyms_lookup_name+0x48/0xb0 btf_parse_fields+0x992/0xce0 map_create+0x591/0x770 __sys_bpf+0x229/0x2410 __x64_sys_bpf+0x1f/0x30 x64_sys_call+0x199/0x9f0 do_syscall_64+0x3b/0xc0 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x7fea56f2cc5d ...... </TASK> ---[ end trace ]---
Fix it by checking the remaining info_cnt in btf_repeat_fields() before repeating the btf fields.
Fixes: 64e8ee814819 ("bpf: look into the types of the fields of a struct type recursively.") Signed-off-by: Hou Tao houtao1@huawei.com Acked-by: Eduard Zingerman eddyz87@gmail.com Link: https://lore.kernel.org/r/20241008071114.3718177-2-houtao@huaweicloud.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/btf.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 9b068afd17953..5f4f1d0bc23a4 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -3528,7 +3528,7 @@ static int btf_get_field_type(const struct btf *btf, const struct btf_type *var_ * (i + 1) * elem_size * where i is the repeat index and elem_size is the size of an element. */ -static int btf_repeat_fields(struct btf_field_info *info, +static int btf_repeat_fields(struct btf_field_info *info, int info_cnt, u32 field_cnt, u32 repeat_cnt, u32 elem_size) { u32 i, j; @@ -3548,6 +3548,12 @@ static int btf_repeat_fields(struct btf_field_info *info, } }
+ /* The type of struct size or variable size is u32, + * so the multiplication will not overflow. + */ + if (field_cnt * (repeat_cnt + 1) > info_cnt) + return -E2BIG; + cur = field_cnt; for (i = 0; i < repeat_cnt; i++) { memcpy(&info[cur], &info[0], field_cnt * sizeof(info[0])); @@ -3592,7 +3598,7 @@ static int btf_find_nested_struct(const struct btf *btf, const struct btf_type * info[i].off += off;
if (nelems > 1) { - err = btf_repeat_fields(info, ret, nelems - 1, t->size); + err = btf_repeat_fields(info, info_cnt, ret, nelems - 1, t->size); if (err == 0) ret *= nelems; else @@ -3686,10 +3692,10 @@ static int btf_find_field_one(const struct btf *btf,
if (ret == BTF_FIELD_IGNORE) return 0; - if (nelems > info_cnt) + if (!info_cnt) return -E2BIG; if (nelems > 1) { - ret = btf_repeat_fields(info, 1, nelems - 1, sz); + ret = btf_repeat_fields(info, info_cnt, 1, nelems - 1, sz); if (ret < 0) return ret; }