mirror of
https://github.com/torvalds/linux.git
synced 2026-08-04 22:38:46 +02:00
2f884d371f
trie_lookup_elem() annotates its rcu_dereference_check() walks with
only rcu_read_lock_bh_held(). Because rcu_dereference_check(p, c)
resolves to "c || rcu_read_lock_held()", this passes for XDP/NAPI and
classic RCU readers but fails for sleepable BPF programs, which enter
via __bpf_prog_enter_sleepable() and hold only rcu_read_lock_trace().
trie_update_elem() and trie_delete_elem() have the same problem in a
different form: they walk the trie with plain rcu_dereference(), which
asserts rcu_read_lock_held() unconditionally. Both are reachable from
sleepable BPF programs via the bpf_map_update_elem / bpf_map_delete_elem
helpers, and from the syscall path under classic rcu_read_lock(). In
the writer paths the trie is actually protected by trie->lock (an
rqspinlock taken across the walk); we never relied on the RCU read-side
lock to keep nodes alive there.
A sleepable LSM hook that ends up touching an LPM trie therefore
triggers lockdep on debug kernels:
=============================
WARNING: suspicious RCU usage
7.1.0-... Tainted: G E
-----------------------------
kernel/bpf/lpm_trie.c:249 suspicious rcu_dereference_check() usage!
1 lock held by net_tests/540:
#0: (rcu_tasks_trace_srcu_struct){....}-{0:0},
at: __bpf_prog_enter_sleepable+0x26/0x280
Call Trace:
dump_stack_lvl
lockdep_rcu_suspicious
trie_lookup_elem
bpf_prog_..._enforce_security_socket_connect
bpf_trampoline_...
security_socket_connect
__sys_connect
do_syscall_64
This is lockdep-only -- no UAF, since Tasks Trace RCU does serialize
against the trie's reclaim path -- but it spams the console once per
distinct callsite on every debug kernel running a sleepable BPF LSM
that touches an LPM trie, which is increasingly common.
For the lookup path, switch the rcu_dereference_check() annotation
from rcu_read_lock_bh_held() to bpf_rcu_lock_held(), which accepts all
three contexts (classic, BH, Tasks Trace). Other map types already
follow this convention.
For trie_update_elem() and trie_delete_elem(), annotate the walks as
rcu_dereference_protected(*p, 1) -- matching trie_free() in the same
file -- since trie->lock is held across the walk. rqspinlock has no
lockdep_map, so the predicate degenerates to '1' rather than
lockdep_is_held(&trie->lock); the protection is real but not
machine-verifiable. trie_get_next_key() also uses bare
rcu_dereference() but is reachable only from the BPF syscall, which
holds classic rcu_read_lock() before dispatching, so it is left
untouched.
Fixes:
|
||
|---|---|---|
| .. | ||
| preload | ||
| arena.c | ||
| arraymap.c | ||
| backtrack.c | ||
| bloom_filter.c | ||
| bpf_cgrp_storage.c | ||
| bpf_inode_storage.c | ||
| bpf_insn_array.c | ||
| bpf_iter.c | ||
| bpf_local_storage.c | ||
| bpf_lru_list.c | ||
| bpf_lru_list.h | ||
| bpf_lsm_proto.c | ||
| bpf_lsm.c | ||
| bpf_struct_ops.c | ||
| bpf_task_storage.c | ||
| btf_iter.c | ||
| btf_relocate.c | ||
| btf.c | ||
| cfg.c | ||
| cgroup_iter.c | ||
| cgroup.c | ||
| check_btf.c | ||
| cnum_defs.h | ||
| cnum.c | ||
| const_fold.c | ||
| core.c | ||
| cpumap.c | ||
| cpumask.c | ||
| crypto.c | ||
| devmap.c | ||
| disasm.c | ||
| disasm.h | ||
| dispatcher.c | ||
| dmabuf_iter.c | ||
| fixups.c | ||
| hashtab.c | ||
| helpers.c | ||
| inode.c | ||
| Kconfig | ||
| kmem_cache_iter.c | ||
| link_iter.c | ||
| liveness.c | ||
| local_storage.c | ||
| log.c | ||
| lpm_trie.c | ||
| Makefile | ||
| map_in_map.c | ||
| map_in_map.h | ||
| map_iter.c | ||
| memalloc.c | ||
| mmap_unlock_work.h | ||
| mprog.c | ||
| net_namespace.c | ||
| offload.c | ||
| percpu_freelist.c | ||
| percpu_freelist.h | ||
| prog_iter.c | ||
| queue_stack_maps.c | ||
| range_tree.c | ||
| range_tree.h | ||
| relo_core.c | ||
| reuseport_array.c | ||
| ringbuf.c | ||
| rqspinlock.c | ||
| rqspinlock.h | ||
| stackmap.c | ||
| states.c | ||
| stream.c | ||
| syscall.c | ||
| sysfs_btf.c | ||
| task_iter.c | ||
| tcx.c | ||
| tnum.c | ||
| token.c | ||
| trampoline.c | ||
| verifier.c | ||