netdev - [PATCH bpf-next] bpf: fix btf_task_struct_ids w/o CONFIG_DEBUG_INFO

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Date:   Tue, 9 Nov 2021 14:24:47 -0800
From:   Song Liu <songliubraving@...com>
To:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>
CC:     <ast@...nel.org>, <daniel@...earbox.net>, <andrii@...nel.org>,
        <kernel-team@...com>, Song Liu <songliubraving@...com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH bpf-next] bpf: fix btf_task_struct_ids w/o CONFIG_DEBUG_INFO_BTF

This fixes KASAN oops like

BUG: KASAN: global-out-of-bounds in task_iter_init+0x212/0x2e7 kernel/bpf/task_iter.c:661
Read of size 4 at addr ffffffff90297404 by task swapper/0/1

CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.15.0-syzkaller #0
Hardware name: ... Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_address_description.constprop.0.cold+0xf/0x309 mm/kasan/report.c:256
__kasan_report mm/kasan/report.c:442 [inline]
kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
task_iter_init+0x212/0x2e7 kernel/bpf/task_iter.c:661
do_one_initcall+0x103/0x650 init/main.c:1295
do_initcall_level init/main.c:1368 [inline]
do_initcalls init/main.c:1384 [inline]
do_basic_setup init/main.c:1403 [inline]
kernel_init_freeable+0x6b1/0x73a init/main.c:1606
kernel_init+0x1a/0x1d0 init/main.c:1497
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>

Reported-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: Song Liu <songliubraving@...com>
---
 kernel/bpf/btf.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index cdb0fba656006..6db929a5826d4 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6342,10 +6342,14 @@ const struct bpf_func_proto bpf_btf_find_by_name_kind_proto = {
 	.arg4_type	= ARG_ANYTHING,
 };

+#ifdef CONFIG_DEBUG_INFO_BTF
 BTF_ID_LIST_GLOBAL(btf_task_struct_ids)
 BTF_ID(struct, task_struct)
 BTF_ID(struct, file)
 BTF_ID(struct, vm_area_struct)
+#else
+u32 btf_task_struct_ids[3];
+#endif

 /* BTF ID set registration API for modules */

-- 
2.30.2