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authorDave Marchevsky <davemarchevsky@fb.com>2023-03-13 14:46:41 -0700
committerAlexei Starovoitov <ast@kernel.org>2023-03-13 16:55:04 -0700
commit9e36a204bd43553a9cd4bd574612cd9a5df791ea (patch)
treebe9a98da078c29e8a0d57da290c6a6be2eb0d690 /include
parent22df776a9a866713d9decfb92b633bcfdb571954 (diff)
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] <TASK> [ 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] </TASK> 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 <ast@kernel.org> Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com> Link: https://lore.kernel.org/r/20230313214641.3731908-1-davemarchevsky@fb.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/bpf.h12
1 files changed, 4 insertions, 8 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 756b85f0d0d3..71cc92a4ba48 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;
};