CVE-2023-52446

In the Linux kernel, the following vulnerability has been resolved: bpf:
Fix a race condition between btf_put() and map_free() When running
./test_progs -j in my local vm with latest kernel, I once hit a kasan
error like below: [ 1887.184724] BUG: KASAN: slab-use-after-free in
bpf_rb_root_free+0x1f8/0x2b0 [ 1887.185599] Read of size 4 at addr
ffff888106806910 by task kworker/u12:2/2830 [ 1887.186498] [ 1887.186712]
CPU: 3 PID: 2830 Comm: kworker/u12:2 Tainted: G OEL
6.7.0-rc3-00699-g90679706d486-dirty #494 [ 1887.188034] Hardware name: QEMU
Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 [ 1887.189618]
Workqueue: events_unbound bpf_map_free_deferred [ 1887.190341] Call Trace:
[ 1887.190666] <TASK> [ 1887.190949] dump_stack_lvl+0xac/0xe0 [
1887.191423] ? nf_tcp_handle_invalid+0x1b0/0x1b0 [ 1887.192019] ?
panic+0x3c0/0x3c0 [ 1887.192449] print_report+0x14f/0x720 [ 1887.192930] ?
preempt_count_sub+0x1c/0xd0 [ 1887.193459] ? __virt_addr_valid+0xac/0x120 [
1887.194004] ? bpf_rb_root_free+0x1f8/0x2b0 [ 1887.194572]
kasan_report+0xc3/0x100 [ 1887.195085] ? bpf_rb_root_free+0x1f8/0x2b0 [
1887.195668] bpf_rb_root_free+0x1f8/0x2b0 [ 1887.196183] ?
__bpf_obj_drop_impl+0xb0/0xb0 [ 1887.196736] ? preempt_count_sub+0x1c/0xd0
[ 1887.197270] ? preempt_count_sub+0x1c/0xd0 [ 1887.197802] ?
_raw_spin_unlock+0x1f/0x40 [ 1887.198319] bpf_obj_free_fields+0x1d4/0x260 [
1887.198883] array_map_free+0x1a3/0x260 [ 1887.199380]
bpf_map_free_deferred+0x7b/0xe0 [ 1887.199943]
process_scheduled_works+0x3a2/0x6c0 [ 1887.200549]
worker_thread+0x633/0x890 [ 1887.201047] ? __kthread_parkme+0xd7/0xf0 [
1887.201574] ? kthread+0x102/0x1d0 [ 1887.202020] kthread+0x1ab/0x1d0 [
1887.202447] ? pr_cont_work+0x270/0x270 [ 1887.202954] ?
kthread_blkcg+0x50/0x50 [ 1887.203444] ret_from_fork+0x34/0x50 [
1887.203914] ? kthread_blkcg+0x50/0x50 [ 1887.204397]
ret_from_fork_asm+0x11/0x20 [ 1887.204913] </TASK> [ 1887.204913] </TASK> [
1887.205209] [ 1887.205416] Allocated by task 2197: [ 1887.205881]
kasan_set_track+0x3f/0x60 [ 1887.206366] __kasan_kmalloc+0x6e/0x80 [
1887.206856] __kmalloc+0xac/0x1a0 [ 1887.207293]
btf_parse_fields+0xa15/0x1480 [ 1887.207836]
btf_parse_struct_metas+0x566/0x670 [ 1887.208387] btf_new_fd+0x294/0x4d0 [
1887.208851] __sys_bpf+0x4ba/0x600 [ 1887.209292] __x64_sys_bpf+0x41/0x50 [
1887.209762] do_syscall_64+0x4c/0xf0 [ 1887.210222]
entry_SYSCALL_64_after_hwframe+0x63/0x6b [ 1887.210868] [ 1887.211074]
Freed by task 36: [ 1887.211460] kasan_set_track+0x3f/0x60 [ 1887.211951]
kasan_save_free_info+0x28/0x40 [ 1887.212485]
____kasan_slab_free+0x101/0x180 [ 1887.213027] __kmem_cache_free+0xe4/0x210
[ 1887.213514] btf_free+0x5b/0x130 [ 1887.213918] rcu_core+0x638/0xcc0 [
1887.214347] __do_softirq+0x114/0x37e The error happens at
bpf_rb_root_free+0x1f8/0x2b0: 00000000000034c0 <bpf_rb_root_free>: ; {
34c0: f3 0f 1e fa endbr64 34c4: e8 00 00 00 00 callq 0x34c9
<bpf_rb_root_free+0x9> 34c9: 55 pushq %rbp 34ca: 48 89 e5 movq %rsp, %rbp
… ; if (rec && rec->refcount_off >= 0 && 36aa: 4d 85 ed testq %r13, %r13
36ad: 74 a9 je 0x3658 <bpf_rb_root_free+0x198> 36af: 49 8d 7d 10 leaq
0x10(%r13), %rdi 36b3: e8 00 00 00 00 callq 0x36b8 <bpf_rb_root_free+0x1f8>
<==== kasan function 36b8: 45 8b 7d 10 movl 0x10(%r13), %r15d <====
use-after-free load 36bc: 45 85 ff testl %r15d, %r15d 36bf: 78 8c js 0x364d
<bpf_rb_root_free+0x18d> So the problem —truncated—

Notes