CVE-2026-64352: bpf: Allow LPM map access from sleepable BPF programs

From: Greg Kroah-Hartman <[email protected]>

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.

The Linux kernel CVE team has assigned CVE-2026-64352 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.14 with commit 694cea395fded425008e93cd90cfdf7a451674af and fixed in 5.15.212 with commit f0967d4f1ba4323a3cb7dc8fdba74dd3a8caaf04
	Issue introduced in 5.14 with commit 694cea395fded425008e93cd90cfdf7a451674af and fixed in 6.1.178 with commit 304ca50582f0c047370f85e13caec456f78c9fcc
	Issue introduced in 5.14 with commit 694cea395fded425008e93cd90cfdf7a451674af and fixed in 6.6.145 with commit ec662a8b2cde01e76b37ccd4b992d0342299e69c
	Issue introduced in 5.14 with commit 694cea395fded425008e93cd90cfdf7a451674af and fixed in 6.12.97 with commit 9bfdf4b81b0e56d47bc6c46c34a46638be716695
	Issue introduced in 5.14 with commit 694cea395fded425008e93cd90cfdf7a451674af and fixed in 6.18.40 with commit 57454944737f3ad9a8703aecbbb79713b513a94b
	Issue introduced in 5.14 with commit 694cea395fded425008e93cd90cfdf7a451674af and fixed in 7.1.4 with commit bd6ad9a6b30498d845413e863fb95c6fab3babe3
	Issue introduced in 5.14 with commit 694cea395fded425008e93cd90cfdf7a451674af and fixed in 7.2-rc1 with commit 2f884d371fafea137afea504d49ee4a7c8d7985b

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-64352
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	kernel/bpf/lpm_trie.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/f0967d4f1ba4323a3cb7dc8fdba74dd3a8caaf04
	https://git.kernel.org/stable/c/304ca50582f0c047370f85e13caec456f78c9fcc
	https://git.kernel.org/stable/c/ec662a8b2cde01e76b37ccd4b992d0342299e69c
	https://git.kernel.org/stable/c/9bfdf4b81b0e56d47bc6c46c34a46638be716695
	https://git.kernel.org/stable/c/57454944737f3ad9a8703aecbbb79713b513a94b
	https://git.kernel.org/stable/c/bd6ad9a6b30498d845413e863fb95c6fab3babe3
	https://git.kernel.org/stable/c/2f884d371fafea137afea504d49ee4a7c8d7985b