TLDRVuln - Cybersecurity Vulnerabilities Made Simple

In the Linux kernel, the following vulnerability has been resolved:

bpf: Address KCSAN report on bpf_lru_list

KCSAN reported a data-race when accessing node->ref.

Although node->ref does not have to be accurate,

take this chance to use a more common READ_ONCE() and WRITE_ONCE()

pattern instead of data_race().

There is an existing bpf_lru_node_is_ref() and bpf_lru_node_set_ref().

This patch also adds bpf_lru_node_clear_ref() to do the

WRITE_ONCE(node->ref, 0) also.

==================================================================

BUG: KCSAN: data-race in __bpf_lru_list_rotate / __htab_lru_percpu_map_update_elem

write to 0xffff888137038deb of 1 bytes by task 11240 on cpu 1:

__bpf_lru_node_move kernel/bpf/bpf_lru_list.c:113 [inline]

__bpf_lru_list_rotate_active kernel/bpf/bpf_lru_list.c:149 [inline]

__bpf_lru_list_rotate+0x1bf/0x750 kernel/bpf/bpf_lru_list.c:240

bpf_lru_list_pop_free_to_local kernel/bpf/bpf_lru_list.c:329 [inline]

bpf_common_lru_pop_free kernel/bpf/bpf_lru_list.c:447 [inline]

bpf_lru_pop_free+0x638/0xe20 kernel/bpf/bpf_lru_list.c:499

prealloc_lru_pop kernel/bpf/hashtab.c:290 [inline]

__htab_lru_percpu_map_update_elem+0xe7/0x820 kernel/bpf/hashtab.c:1316

bpf_percpu_hash_update+0x5e/0x90 kernel/bpf/hashtab.c:2313

bpf_map_update_value+0x2a9/0x370 kernel/bpf/syscall.c:200

generic_map_update_batch+0x3ae/0x4f0 kernel/bpf/syscall.c:1687

bpf_map_do_batch+0x2d9/0x3d0 kernel/bpf/syscall.c:4534

__sys_bpf+0x338/0x810

__do_sys_bpf kernel/bpf/syscall.c:5096 [inline]

__se_sys_bpf kernel/bpf/syscall.c:5094 [inline]

__x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5094

do_syscall_x64 arch/x86/entry/common.c:50 [inline]

do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80

entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff888137038deb of 1 bytes by task 11241 on cpu 0:

bpf_lru_node_set_ref kernel/bpf/bpf_lru_list.h:70 [inline]

__htab_lru_percpu_map_update_elem+0x2f1/0x820 kernel/bpf/hashtab.c:1332