From bc235cdb423a2daed6f337676006a66557429cd1 Mon Sep 17 00:00:00 2001 From: Song Liu Date: Thu, 25 Feb 2021 15:43:15 -0800 Subject: bpf: Prevent deadlock from recursive bpf_task_storage_[get|delete] BPF helpers bpf_task_storage_[get|delete] could hold two locks: bpf_local_storage_map_bucket->lock and bpf_local_storage->lock. Calling these helpers from fentry/fexit programs on functions in bpf_*_storage.c may cause deadlock on either locks. Prevent such deadlock with a per cpu counter, bpf_task_storage_busy. We need this counter to be global, because the two locks here belong to two different objects: bpf_local_storage_map and bpf_local_storage. If we pick one of them as the owner of the counter, it is still possible to trigger deadlock on the other lock. For example, if bpf_local_storage_map owns the counters, it cannot prevent deadlock on bpf_local_storage->lock when two maps are used. Signed-off-by: Song Liu Signed-off-by: Alexei Starovoitov Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/bpf/20210225234319.336131-3-songliubraving@fb.com --- kernel/bpf/bpf_inode_storage.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/bpf/bpf_inode_storage.c') diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storage.c index 6639640523c0..da753721457c 100644 --- a/kernel/bpf/bpf_inode_storage.c +++ b/kernel/bpf/bpf_inode_storage.c @@ -237,7 +237,7 @@ static void inode_storage_map_free(struct bpf_map *map) smap = (struct bpf_local_storage_map *)map; bpf_local_storage_cache_idx_free(&inode_cache, smap->cache_idx); - bpf_local_storage_map_free(smap); + bpf_local_storage_map_free(smap, NULL); } static int inode_storage_map_btf_id; -- cgit v1.2.3