linux-stable.git/kernel/bpf/helpers.c, branch linux-rolling-stable

bpf: Fix NULL pointer dereference in bpf_task_from_vpid()

2026-07-24T14:19:37+00:00

[ Upstream commit 50dff00615522f3ec03449680ca23beb4cfc549c ]

bpf_task_from_vpid() looks up a task in the pid namespace of the
current task, via find_task_by_vpid():

  find_task_by_vpid(vpid)
    find_task_by_pid_ns(vpid, task_active_pid_ns(current))
      find_pid_ns(nr, ns) -> idr_find(&ns->idr, nr)

cgroup_skb programs run in softirq, which may interrupt a task that is
itself in do_exit(). Once that task has passed
exit_notify() -> release_task() -> __unhash_process(), its thread_pid is
cleared, so task_active_pid_ns(current) returns NULL and find_pid_ns()
dereferences &NULL->idr:

  BUG: kernel NULL pointer dereference, address: 0000000000000050
  RIP: 0010:idr_find+0x11/0x30 lib/idr.c:176
  Call Trace:
   
   find_pid_ns kernel/pid.c:370 [inline]
   find_task_by_pid_ns+0x3b/0xe0 kernel/pid.c:485
   bpf_task_from_vpid+0x5b/0x200 kernel/bpf/helpers.c:2916
   bpf_prog_run_array_cg+0x17e/0x530 kernel/bpf/cgroup.c:81
   __cgroup_bpf_run_filter_skb+0x12b/0x250 kernel/bpf/cgroup.c:1612
   sk_filter_trim_cap+0x1dc/0x4c0 net/core/filter.c:148
   tcp_v4_rcv+0x18d1/0x2200 net/ipv4/tcp_ipv4.c:2223
   
   
   do_exit+0xa63/0x1270 kernel/exit.c:1010
   get_signal+0x141c/0x1530 kernel/signal.c:3037

Bail out when current has no pid namespace.

Fixes: 675c3596ff32 ("bpf: Add bpf_task_from_vpid() kfunc")
Signed-off-by: Sechang Lim 
Acked-by: Leon Hwang 
Link: https://lore.kernel.org/bpf/20260608050001.2545245-1-rhkrqnwk98@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi 
Signed-off-by: Sasha Levin

bpf: Clear rb node linkage when freeing bpf_rb_root

2026-07-24T14:19:34+00:00

[ Upstream commit 4a7910ee060d8ce55612f5b3cc267f3a265a3cec ]

bpf_rb_root_free() detaches the root by copying the current rb_root_cached
and then replacing the live root with RB_ROOT_CACHED. It then walks the
copied root and drops each object contained in the tree.

This leaves the rb node state intact while dropping the object. If the
object is refcounted and survives the drop, its bpf_rb_node_kern still
contains an owner pointer to the freed root and stale rb tree linkage. If
a later bpf_rb_root allocation reuses the same address, bpf_rbtree_remove()
can incorrectly pass the owner check and call rb_erase_cached() on a node
whose rb pointers belong to the old tree.

Mirror the list draining behavior by marking nodes as busy while the root
is being detached, then clear the rb node and release the owner before
dropping the containing object. This makes surviving nodes unowned and
safe to reject from remove or accept for a later add.

Fixes: 9c395c1b99bd ("bpf: Add basic bpf_rb_{root,node} support")
Signed-off-by: Kaitao Cheng 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/r/20260605094143.5509-1-kaitao.cheng@linux.dev
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Sasha Levin

bpf: Reject NULL data/sig in bpf_verify_pkcs7_signature

2026-05-20T03:12:05+00:00

__bpf_dynptr_data() can return NULL (FILE dynptrs, any non-contiguous
backing). bpf_verify_pkcs7_signature() forwards the pointer to
verify_pkcs7_signature() unchecked, causing a NULL deref in
asn1_ber_decoder() reachable from a sleepable BPF LSM at lsm.s/bpf.

NULL-check both pointers and reject with -EINVAL. Mirrors the guards
already in kernel/bpf/crypto.c.

Fixes: 865b0566d8f1 ("bpf: Add bpf_verify_pkcs7_signature() kfunc")
Reported-by: Xianrui Dong 
Signed-off-by: KP Singh 
Reviewed-by: Amery Hung 
Acked-by: Song Liu 
Acked-by: Daniel Borkmann 
Link: https://lore.kernel.org/bpf/20260520024059.313468-1-kpsingh@kernel.org
Signed-off-by: Kumar Kartikeya Dwivedi

bpf: allow UTF-8 literals in bpf_bprintf_prepare()

2026-04-16T22:53:32+00:00

bpf_bprintf_prepare() only needs ASCII parsing for conversion
specifiers. Plain text can safely carry bytes >= 0x80, so allow
UTF-8 literals outside '%' sequences while keeping ASCII control
bytes rejected and format specifiers ASCII-only.

This keeps existing parsing rules for format directives unchanged,
while allowing helpers such as bpf_trace_printk() to emit UTF-8
literal text.

Update test_snprintf_negative() in the same commit so selftests keep
matching the new plain-text vs format-specifier split during bisection.

Fixes: 48cac3f4a96d ("bpf: Implement formatted output helpers with bstr_printf")
Signed-off-by: Yihan Ding 
Acked-by: Paul Chaignon 
Link: https://lore.kernel.org/r/20260416120142.1420646-2-dingyihan@uniontech.com
Signed-off-by: Alexei Starovoitov

bpf: Retire rcu_trace_implies_rcu_gp()

2026-04-07T19:24:49+00:00

RCU Tasks Trace grace period implies RCU grace period, and this
guarantee is expected to remain in the future. Only BPF is the user of
this predicate, hence retire the API and clean up all in-tree users.

RCU Tasks Trace is now implemented on SRCU-fast and its grace period
mechanism always has at least one call to synchronize_rcu() as it is
required for SRCU-fast's correctness (it replaces the smp_mb() that
SRCU-fast readers skip). So, RCU-tt GP will always imply RCU GP.

Reviewed-by: Puranjay Mohan 
Reviewed-by: Paul E. McKenney 
Signed-off-by: Kumar Kartikeya Dwivedi 
Link: https://lore.kernel.org/r/20260407162234.785270-1-memxor@gmail.com
Signed-off-by: Alexei Starovoitov

bpf: Migrate dynptr file to kmalloc_nolock

2026-04-02T16:31:42+00:00

Replace bpf_mem_alloc/bpf_mem_free with kmalloc_nolock/kfree_nolock for
bpf_dynptr_file_impl, continuing the migration away from bpf_mem_alloc
now that kmalloc can be used from NMI context.

freader_cleanup() runs before kfree_nolock() while the dynptr still
holds exclusive access, so plain kfree_nolock() is safe — no concurrent
readers can access the object.

Signed-off-by: Mykyta Yatsenko 
Acked-by: Andrii Nakryiko 
Acked-by: Kumar Kartikeya Dwivedi 
Link: https://lore.kernel.org/r/20260330-kmalloc_special-v2-2-c90403f92ff0@meta.com
Signed-off-by: Alexei Starovoitov

bpf: Migrate bpf_task_work to kmalloc_nolock

2026-04-02T16:31:42+00:00

Replace bpf_mem_alloc/bpf_mem_free with
kmalloc_nolock/kfree_rcu for bpf_task_work_ctx.

Replace guard(rcu_tasks_trace)() with guard(rcu)() in
bpf_task_work_irq(). The function only accesses ctx struct members
(not map values), so tasks trace protection is not needed - regular
RCU is sufficient since ctx is freed via kfree_rcu. The guard in
bpf_task_work_callback() remains as tasks trace since it accesses map
values from process context.

Sleepable BPF programs hold rcu_read_lock_trace but not
regular rcu_read_lock. Since kfree_rcu
waits for a regular RCU grace period, the ctx memory can be freed
while a sleepable program is still running. Add scoped_guard(rcu)
around the pointer read and refcount tryget in
bpf_task_work_acquire_ctx to close this race window.

Since kfree_rcu uses call_rcu internally which is not safe from
NMI context, defer destruction via irq_work when irqs are disabled.

For the lost-cmpxchg path the ctx was never published, so
kfree_nolock is safe.

Signed-off-by: Mykyta Yatsenko 
Acked-by: Kumar Kartikeya Dwivedi 
Link: https://lore.kernel.org/r/20260330-kmalloc_special-v2-1-c90403f92ff0@meta.com
Signed-off-by: Alexei Starovoitov

bpf: Support struct btf_struct_meta via KF_IMPLICIT_ARGS

2026-03-29T16:56:06+00:00

The following kfuncs currently accept void *meta__ign argument:
  * bpf_obj_new_impl
  * bpf_obj_drop_impl
  * bpf_percpu_obj_new_impl
  * bpf_percpu_obj_drop_impl
  * bpf_refcount_acquire_impl
  * bpf_list_push_back_impl
  * bpf_list_push_front_impl
  * bpf_rbtree_add_impl

The __ign suffix is an indicator for the verifier to skip the argument
in check_kfunc_args(). Then, in fixup_kfunc_call() the verifier may
set the value of this argument to struct btf_struct_meta *
kptr_struct_meta from insn_aux_data.

BPF programs must pass a dummy NULL value when calling these kfuncs.

Additionally, the list and rbtree _impl kfuncs also accept an implicit
u64 argument, which doesn't require __ign suffix because it's a
scalar, and BPF programs explicitly pass 0.

Add new kfuncs with KF_IMPLICIT_ARGS [1], that correspond to each
_impl kfunc accepting meta__ign. The existing _impl kfuncs remain
unchanged for backwards compatibility.

To support this, add "btf_struct_meta" to the list of recognized
implicit argument types in resolve_btfids.

Implement is_kfunc_arg_implicit() in the verifier, that determines
implicit args by inspecting both a non-_impl BTF prototype of the
kfunc.

Update the special_kfunc_list in the verifier and relevant checks to
support both the old _impl and the new KF_IMPLICIT_ARGS variants of
btf_struct_meta users.

[1] https://lore.kernel.org/bpf/20260120222638.3976562-1-ihor.solodrai@linux.dev/

Signed-off-by: Ihor Solodrai 
Acked-by: Jiri Olsa 
Link: https://lore.kernel.org/r/20260327203241.3365046-1-ihor.solodrai@linux.dev
Signed-off-by: Alexei Starovoitov

s390: Introduce bpf_get_lowcore() kfunc

2026-03-03T16:35:07+00:00

Implementing BPF version of preempt_count() requires accessing lowcore
from BPF. Since lowcore can be relocated, open-coding
(struct lowcore *)0 does not work, so add a kfunc.

Signed-off-by: Ilya Leoshkevich 
Link: https://lore.kernel.org/r/20260217160813.100855-2-iii@linux.ibm.com
Signed-off-by: Alexei Starovoitov

Convert 'alloc_obj' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51+00:00

This was done entirely with mindless brute force, using

    git grep -l '\