In the Linux kernel, the following vulnerability has been resolved:
bpf: Allow LPM map access from sleepable BPF programs
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.
Metrics
Affected Vendors & Products
| Vendors | Products |
|---|---|
| Linux |
|
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References
History
Sat, 25 Jul 2026 09:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: bpf: Allow LPM map access from sleepable BPF programs 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. | |
| Title | bpf: Allow LPM map access from sleepable BPF programs | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-07-25T08:50:11.522Z
Reserved: 2026-07-19T15:36:31.782Z
Link: CVE-2026-64352
Vulnrichment
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NVD
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Redhat
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OpenCVE Enrichment
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