From: Dave Marchevsky Date: Mon, 13 Mar 2023 21:46:41 +0000 (-0700) Subject: bpf: Disable migration when freeing stashed local kptr using obj drop X-Git-Tag: v6.6.7~2736^2~129^2~93 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=9e36a204bd43553a9cd4bd574612cd9a5df791ea;p=platform%2Fkernel%2Flinux-starfive.git bpf: Disable migration when freeing stashed local kptr using obj drop When a local kptr is stashed in a map and freed when the map goes away, currently an error like the below appears: [ 39.195695] BUG: using smp_processor_id() in preemptible [00000000] code: kworker/u32:15/2875 [ 39.196549] caller is bpf_mem_free+0x56/0xc0 [ 39.196958] CPU: 15 PID: 2875 Comm: kworker/u32:15 Tainted: G O 6.2.0-13016-g22df776a9a86 #4477 [ 39.197897] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014 [ 39.198949] Workqueue: events_unbound bpf_map_free_deferred [ 39.199470] Call Trace: [ 39.199703] [ 39.199911] dump_stack_lvl+0x60/0x70 [ 39.200267] check_preemption_disabled+0xbf/0xe0 [ 39.200704] bpf_mem_free+0x56/0xc0 [ 39.201032] ? bpf_obj_new_impl+0xa0/0xa0 [ 39.201430] bpf_obj_free_fields+0x1cd/0x200 [ 39.201838] array_map_free+0xad/0x220 [ 39.202193] ? finish_task_switch+0xe5/0x3c0 [ 39.202614] bpf_map_free_deferred+0xea/0x210 [ 39.203006] ? lockdep_hardirqs_on_prepare+0xe/0x220 [ 39.203460] process_one_work+0x64f/0xbe0 [ 39.203822] ? pwq_dec_nr_in_flight+0x110/0x110 [ 39.204264] ? do_raw_spin_lock+0x107/0x1c0 [ 39.204662] ? lockdep_hardirqs_on_prepare+0xe/0x220 [ 39.205107] worker_thread+0x74/0x7a0 [ 39.205451] ? process_one_work+0xbe0/0xbe0 [ 39.205818] kthread+0x171/0x1a0 [ 39.206111] ? kthread_complete_and_exit+0x20/0x20 [ 39.206552] ret_from_fork+0x1f/0x30 [ 39.206886] This happens because the call to __bpf_obj_drop_impl I added in the patch adding support for stashing local kptrs doesn't disable migration. Prior to that patch, __bpf_obj_drop_impl logic only ran when called by a BPF progarm, whereas now it can be called from map free path, so it's necessary to explicitly disable migration. Also, refactor a bit to just call __bpf_obj_drop_impl directly instead of bothering w/ dtor union and setting pointer-to-obj_drop. Fixes: c8e187540914 ("bpf: Support __kptr to local kptrs") Reported-by: Alexei Starovoitov Signed-off-by: Dave Marchevsky Link: https://lore.kernel.org/r/20230313214641.3731908-1-davemarchevsky@fb.com Signed-off-by: Alexei Starovoitov --- diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 756b85f..71cc92a 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -190,18 +190,14 @@ enum btf_field_type { }; typedef void (*btf_dtor_kfunc_t)(void *); -typedef void (*btf_dtor_obj_drop)(void *, const struct btf_record *); struct btf_field_kptr { struct btf *btf; struct module *module; - union { - /* dtor used if btf_is_kernel(btf), otherwise the type - * is program-allocated and obj_drop is used - */ - btf_dtor_kfunc_t dtor; - btf_dtor_obj_drop obj_drop; - }; + /* dtor used if btf_is_kernel(btf), otherwise the type is + * program-allocated, dtor is NULL, and __bpf_obj_drop_impl is used + */ + btf_dtor_kfunc_t dtor; u32 btf_id; }; diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 66fad7a..b7e5a55 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -3551,8 +3551,6 @@ static int btf_find_field(const struct btf *btf, const struct btf_type *t, return -EINVAL; } -extern void __bpf_obj_drop_impl(void *p, const struct btf_record *rec); - static int btf_parse_kptr(const struct btf *btf, struct btf_field *field, struct btf_field_info *info) { @@ -3578,7 +3576,7 @@ static int btf_parse_kptr(const struct btf *btf, struct btf_field *field, /* Type exists only in program BTF. Assume that it's a MEM_ALLOC * kptr allocated via bpf_obj_new */ - field->kptr.dtor = (void *)&__bpf_obj_drop_impl; + field->kptr.dtor = NULL; id = info->kptr.type_id; kptr_btf = (struct btf *)btf; btf_get(kptr_btf); diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 0684feb..5b88301 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -650,6 +650,8 @@ void bpf_obj_free_timer(const struct btf_record *rec, void *obj) bpf_timer_cancel_and_free(obj + rec->timer_off); } +extern void __bpf_obj_drop_impl(void *p, const struct btf_record *rec); + void bpf_obj_free_fields(const struct btf_record *rec, void *obj) { const struct btf_field *fields; @@ -679,9 +681,11 @@ void bpf_obj_free_fields(const struct btf_record *rec, void *obj) pointee_struct_meta = btf_find_struct_meta(field->kptr.btf, field->kptr.btf_id); WARN_ON_ONCE(!pointee_struct_meta); - field->kptr.obj_drop(xchgd_field, pointee_struct_meta ? - pointee_struct_meta->record : - NULL); + migrate_disable(); + __bpf_obj_drop_impl(xchgd_field, pointee_struct_meta ? + pointee_struct_meta->record : + NULL); + migrate_enable(); } else { field->kptr.dtor(xchgd_field); }