bpf: Fix refcount_acquire handling for borrowed kptrs

[kernel-patches-daemon-bpf]

Pull request for series with
subject: bpf: Fix refcount_acquire handling for borrowed kptrs
version: 4
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1145728

[kernel-patches-daemon-bpf]

Upstream branch: 806c1a1
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=1145728
version: 4

[kernel-patches-daemon-bpf]

Upstream branch: aacd13e
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=1145728
version: 4

[kernel-patches-review-bot]

commit ce47b900d1feda10042f013b89930295e2ff03c7
Author: Ning Ding <dingning04@gmail.com>

selftests/bpf: Test untrusted allocated-object pointers

This commit adds negative tests for bpf_refcount_acquire() and write
operations on pointers after RCU protection ends, covering both object
layouts tested by the verifier (node_refcount_only and node_data).

Link: https://lore.kernel.org/r/20260726021304.97ED91F000E9@smtp.kernel.org

> diff --git a/tools/testing/selftests/bpf/progs/refcounted_kptr.c b/tools/testing/selftests/bpf/progs/refcounted_kptr.c
> index fd35093285c0d..383c5b1b7111f 100644
> --- a/tools/testing/selftests/bpf/progs/refcounted_kptr.c
> +++ b/tools/testing/selftests/bpf/progs/refcounted_kptr.c
> @@ -893,6 +893,106 @@ long refcount_acquire_rcu_map_kptr_null_checked(void *ctx)
>  	return 0;
>  }
>
> +SEC("?syscall")
> +__success
> +long map_kptr_read_after_rcu_unlock(void *ctx)

A reviewer noted in v3 that the tests use TC programs with implicit RCU
protection, causing pointers not to become untrusted as intended, and
specifically suggested: "The right fix might be to use fentry.s for these
tests to trigger untrusted marking of pointers."

v4 uses SEC("?syscall") instead. While syscall programs are sleepable and
may trigger untrusted marking, does this section annotation achieve the
same behavior Kumar recommended fentry.s for? The deviation from the
specific suggestion wasn't discussed in the v4 thread.

> +{
> +	struct map_value_refcount_only *mapval;
> +	struct node_refcount_only *n;
> +	int idx = 0;
> +
> +	mapval = bpf_map_lookup_elem(&stashed_refcount_only, &idx);
> +	if (!mapval)
> +		return 0;
> +
> +	bpf_rcu_read_lock();
> +	n = mapval->node;
> +	if (!n) {
> +		bpf_rcu_read_unlock();
> +		return 0;
> +	}
> +	bpf_rcu_read_unlock();
> +
> +	return n->key;
> +}
> +
> +SEC("?syscall")
> +__failure __msg("is neither owning or non-owning ref")
> +long refcount_acquire_graph_after_rcu_unlock(void *ctx)
> +{
> +	struct map_value *mapval;
> +	struct node_data *n, *m;
> +	int idx = 0;
> +
> +	mapval = bpf_map_lookup_elem(&stashed_nodes, &idx);
> +	if (!mapval)
> +		return 0;
> +
> +	bpf_rcu_read_lock();
> +	n = mapval->node;
> +	if (!n) {
> +		bpf_rcu_read_unlock();
> +		return 0;
> +	}
> +	bpf_rcu_read_unlock();
> +
> +	m = bpf_refcount_acquire(n);
> +	if (m)
> +		bpf_obj_drop(m);
> +
> +	return 0;
> +}
> +
> +SEC("?syscall")
> +__failure __msg("only read is supported")
> +long graph_map_kptr_write_after_rcu_unlock(void *ctx)
> +{
> +	struct map_value *mapval;
> +	struct node_data *n;
> +	int idx = 0;
> +
> +	mapval = bpf_map_lookup_elem(&stashed_nodes, &idx);
> +	if (!mapval)
> +		return 1;
> +
> +	bpf_rcu_read_lock();
> +	n = mapval->node;
> +	if (!n) {
> +		bpf_rcu_read_unlock();
> +		return 2;
> +	}
> +	bpf_rcu_read_unlock();
> +
> +	n->key = 1;
> +	return 0;
> +}

Does this test actually verify the fix? The "only read is supported"
rejection comes from the PTR_UNTRUSTED check in check_ptr_to_btf_access():

    if (atype != BPF_READ && (type_flag(reg->type) & PTR_UNTRUSTED)) {
            verbose(env, "only read is supported\n");
            return -EACCES;
    }

This check is unchanged in the pre-series tree and rejects writes through
any PTR_UNTRUSTED register for both object layouts. A kernel missing the
series fix would still fail this test with the same message, so the test
wouldn't catch a revert.

> +
> +SEC("?syscall")
> +__success
> +long graph_map_kptr_read_after_spin_unlock(void *ctx)
> +{
> +	struct map_value *mapval;
> +	struct node_data *n;
> +	int idx = 0;
> +
> +	mapval = bpf_map_lookup_elem(&stashed_nodes, &idx);
> +	if (!mapval)
> +		return 0;
> +
> +	bpf_rcu_read_lock();
> +	n = mapval->node;
> +	if (!n) {
> +		bpf_rcu_read_unlock();
> +		return 0;
> +	}
> +	bpf_rcu_read_unlock();
> +
> +	bpf_spin_lock(&lock);
> +	bpf_spin_unlock(&lock);
> +
> +	return n->key;
> +}

Is __success correct for this read? After bpf_rcu_read_unlock() in a
sleepable program, the pointer gains PTR_UNTRUSTED but keeps NON_OWN_REF
because the fix excludes PTR_UNTRUSTED from type_is_ptr_alloc_obj().

At the load, the type is PTR_TO_BTF_ID | MEM_ALLOC | PTR_UNTRUSTED |
NON_OWN_REF. The bpf_convert_ctx_accesses() switch in
kernel/bpf/fixups.c lists these BPF_PROBE_MEM cases:

    case PTR_TO_BTF_ID | PTR_UNTRUSTED:
    case PTR_TO_BTF_ID | MEM_ALLOC | PTR_UNTRUSTED:

but not the NON_OWN_REF variant, so the switch falls through and the load
stays a plain BPF_MEM access with no exception-table entry.

The object is freed via bpf_mem_free_rcu(), so in a sleepable syscall
program that has left the RCU critical section, a grace period can elapse
and the page can be returned to the allocator before the load executes,
causing an unprotected fault.

Pre-series, invalidate_non_owning_refs() at bpf_spin_unlock() killed this
register because type_is_non_owning_ref() was true. Now that
type_is_ptr_alloc_obj() excludes PTR_UNTRUSTED, type_is_non_owning_ref()
returns false and the stale register survives.

The sibling test map_kptr_read_after_rcu_unlock (node_refcount_only, no
graph node, hence no NON_OWN_REF) does match a BPF_PROBE_MEM case and gets
the probe rewrite. Should either fixups.c gain a NON_OWN_REF case and this
test document the probe path, or should NON_OWN_REF be stripped in
invalidate_rcu_protected_refs()?

> +
>  static long __stash_map_empty_xchg(struct node_data *n, int idx)
>  {
>  	struct map_value *mapval = bpf_map_lookup_elem(&stashed_nodes, &idx);
> diff --git a/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c b/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c
> index acd3e81a39168..0cc4cbd0c81b1 100644
> --- a/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c
> +++ b/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c
> @@ -127,6 +127,33 @@ long refcount_acquire_rcu_map_kptr_unchecked_drop(void *ctx)
>  	return 0;
>  }
>
> +SEC("?syscall")
> +__failure __msg("is neither owning or non-owning ref")
> +long refcount_acquire_after_rcu_unlock(void *ctx)
> +{
> +	struct map_value_refcount_only *mapval;
> +	struct node_refcount_only *n, *m;
> +	int idx = 0;
> +
> +	mapval = bpf_map_lookup_elem(&stashed_refcount_only, &idx);
> +	if (!mapval)
> +		return 1;
> +
> +	bpf_rcu_read_lock();
> +	n = mapval->node;
> +	if (!n) {
> +		bpf_rcu_read_unlock();
> +		return 2;
> +	}
> +	bpf_rcu_read_unlock();
> +
> +	m = bpf_refcount_acquire(n);
> +	if (m)
> +		bpf_obj_drop(m);
> +
> +	return 0;
> +}
> +
>  SEC("?tc")
>  __failure __msg("Unreleased reference id=3 alloc_insn={{[0-9]+}}")
>  long rbtree_refcounted_node_ref_escapes_owning_input(void *ctx)

The commit message states:

> The verifier previously allowed pointers used after RCU protection ended
> to reach bpf_refcount_acquire() and, for one object layout, a direct write.
> If the object was freed and reused, these operations could access stale
> memory.
>
> Add tests that keep BPF_PROBE_MEM reads accepted but reject reference
> acquisition and direct writes after RCU protection ends. Cover both tested
> object layouts.

Is the description fully accurate?

The "direct write" was never allowed for any object layout. The
PTR_UNTRUSTED check in check_ptr_to_btf_access() predates the series and
rejects writes through any PTR_UNTRUSTED register for both node_data and
node_refcount_only.

The claim "keep BPF_PROBE_MEM reads accepted ... Cover both tested object
layouts" is only true for node_refcount_only (map_kptr_read_after_rcu_unlock).
The node_data read (graph_map_kptr_read_after_spin_unlock) ends up with
PTR_TO_BTF_ID | MEM_ALLOC | PTR_UNTRUSTED | NON_OWN_REF, a combination
missing from bpf_convert_ctx_accesses() in kernel/bpf/fixups.c, so it
stays a plain BPF_MEM load without probe rewrite.

The genuinely new coverage is the two bpf_refcount_acquire() tests. Would
it be more accurate to scope the description to those plus the
refcount-only read?

---

AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

In-Reply-To-Subject: selftests/bpf: Test untrusted allocated-object pointers
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/31745514567

[kernel-patches-daemon-bpf]

Upstream branch: 259d60f
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=1145728
version: 4

[kernel-patches-daemon-bpf]

Forwarding comment 5286949115 via email
In-Reply-To: 20260813211533.290256-5-dingning04@gmail.com
Patch: https://patchwork.kernel.org/project/netdevbpf/patch/20260813211533.290256-5-dingning04@gmail.com/

[kernel-patches-review-bot]

commit 74e3d640b012b7017df1aa70c16a13e5befabc2e
Author: Ning Ding <dingning04@gmail.com>

bpf: Reject untrusted allocated-object pointers

This commit tightens type_is_ptr_alloc_obj() to reject PTR_UNTRUSTED
pointers, preventing stale pointers from being passed to
bpf_refcount_acquire(). It adds type_is_untrusted_ptr_alloc_obj() to
preserve BPF_PROBE_MEM read support.

Link: https://lore.kernel.org/r/20260726021304.97ED91F000E9@smtp.kernel.org

> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> index 27b43fda9b178..22fcd01c3cceb 100644
> --- a/include/linux/bpf_verifier.h
> +++ b/include/linux/bpf_verifier.h
> @@ -1341,7 +1341,16 @@ static inline bool bpf_type_has_unsafe_modifiers(u32 type)
>
>  static inline bool type_is_ptr_alloc_obj(u32 type)
>  {
> -	return base_type(type) == PTR_TO_BTF_ID && type_flag(type) & MEM_ALLOC;
> +	return base_type(type) == PTR_TO_BTF_ID &&
> +	       type_flag(type) & MEM_ALLOC &&
> +	       !(type_flag(type) & PTR_UNTRUSTED);
> +}
> +
> +static inline bool type_is_untrusted_ptr_alloc_obj(u32 type)
> +{
> +	return base_type(type) == PTR_TO_BTF_ID &&
> +	       type_flag(type) & MEM_ALLOC &&
> +	       type_flag(type) & PTR_UNTRUSTED;
>  }
>
>  static inline bool type_is_non_owning_ref(u32 type)

Does adding the PTR_UNTRUSTED check to type_is_ptr_alloc_obj() also
change type_is_non_owning_ref()?

Looking at the definition in include/linux/bpf_verifier.h:

    static inline bool type_is_non_owning_ref(u32 type)
    {
            return type_is_ptr_alloc_obj(type) && type_flag(type) & NON_OWN_REF;
    }

It calls type_is_ptr_alloc_obj(), so after this patch it will also
reject PTR_UNTRUSTED registers. The commit message describes tightening
bpf_refcount_acquire() but doesn't mention this transitive effect.

Can this affect invalidate_non_owning_refs() in sleepable programs?

Consider a sleepable program using bpf_spin_lock() around graph
operations (which is a supported pattern, as seen in
tools/testing/selftests/bpf/progs/refcounted_kptr.c tests like
rbtree_sleepable_rcu).

When the program calls bpf_spin_unlock(), process_spin_lock() runs:

    if (!in_rcu_cs(env))
            invalidate_rcu_protected_refs(env);
    invalidate_non_owning_refs(env);

For sleepable programs, in_rcu_cs() returns false, so
invalidate_rcu_protected_refs() runs first. That function does:

    reg->type &= ~(MEM_RCU | PTR_MAYBE_NULL);
    reg->type |= PTR_UNTRUSTED;

A register holding a non-owning ref to a stashed graph node starts as
PTR_TO_BTF_ID|MEM_ALLOC|NON_OWN_REF|MEM_RCU (set by
btf_ld_kptr_type()/ref_set_non_owning() when loading from the graph).
After invalidate_rcu_protected_refs() it becomes
PTR_TO_BTF_ID|MEM_ALLOC|NON_OWN_REF|PTR_UNTRUSTED.

The immediately following invalidate_non_owning_refs() only acts on
registers where type_is_non_owning_ref() returns true. But after this
patch, type_is_non_owning_ref() returns false for registers with
PTR_UNTRUSTED.

So these registers that should be invalidated instead survive
bpf_spin_unlock() as live, readable pointers. Is this intended?

Pre-patch they would have been invalidated by mark_reg_invalid() in
invalidate_non_owning_refs(). Post-patch they escape invalidation.

The commit message states untrusted pointers "are still allowed for
BPF_PROBE_MEM reads," but does the BPF_PROBE_MEM conversion actually
work for the NON_OWN_REF variant?

Looking at kernel/bpf/fixups.c, the probe conversion logic has:

    case PTR_TO_BTF_ID | MEM_ALLOC | PTR_UNTRUSTED:
            /* probe mem access */
            ...
    default:
            continue;

It has a case for the plain MEM_ALLOC|PTR_UNTRUSTED type, but no case
for PTR_TO_BTF_ID|MEM_ALLOC|NON_OWN_REF|PTR_UNTRUSTED. So a load
through the surviving register is emitted as a plain load with no
exception-table entry, which would fault in the kernel instead of
returning zero.

> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index bc021c8c8fbf7..c3a11c98cd451 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -5820,7 +5820,13 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env,
>  			return -EACCES;
>  		}
>
> -		if (type_is_alloc(reg->type) && !type_is_non_owning_ref(reg->type) &&
> +		/*
> +		 * Skip this referenced-ID sanity check for untrusted allocated objects;
> +		 * the access check above already rejects writes through them.
> +		 */
> +		if (type_is_alloc(reg->type) &&
> +		    !type_is_untrusted_ptr_alloc_obj(reg->type) &&
> +		    !type_is_non_owning_ref(reg->type) &&
>  		    !(reg->type & MEM_RCU) && !reg_is_referenced(env, reg)) {
>  			verifier_bug(env, "allocated object must have a referenced id");
>  			return -EFAULT;

This change allows the demoted PTR_UNTRUSTED|NON_OWN_REF registers to
reach mark_btf_ld_reg() instead of hitting the sanity assertion, which
opens the path for the read-through described above.

---

AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

In-Reply-To-Subject: bpf: Reject untrusted allocated-object pointers
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/31745514567

[kernel-patches-review-bot]

commit a5fc03ca4cde9760d902959464c265daa785a854
Author: Ning Ding <dingning04@gmail.com>

selftests/bpf: Test refcount_acquire return nullability

The verifier could accept an unchecked bpf_refcount_acquire() result for
a borrowed RCU-loaded map kptr. This commit adds tests showing that an
owned input remains non-NULL, a checked borrowed result is accepted, and
an unchecked borrowed result is rejected.

> diff --git a/tools/testing/selftests/bpf/progs/refcounted_kptr.c b/tools/testing/selftests/bpf/progs/refcounted_kptr.c
> index 61906f48025cc..fd35093285c0d 100644
> --- a/tools/testing/selftests/bpf/progs/refcounted_kptr.c
> +++ b/tools/testing/selftests/bpf/progs/refcounted_kptr.c

[ ... ]

> @@ -832,6 +848,51 @@ long rbtree_refcounted_node_ref_escapes_owning_input(void *ctx)
>  	return 0;
>  }
>
> +SEC("tc")
> +__success
> +long refcount_acquire_owning_input_no_null_check(void *ctx)
> +{
> +	struct node_refcount_only *n, *m;
> +
> +	n = bpf_obj_new(typeof(*n));
> +	if (!n)
> +		return 1;
> +
> +	m = bpf_refcount_acquire(n);
> +	bpf_obj_drop(m);
> +	bpf_obj_drop(n);
> +
> +	return 0;
> +}
> +
> +SEC("tc")
> +__success
> +long refcount_acquire_rcu_map_kptr_null_checked(void *ctx)
> +{
> +	struct map_value_refcount_only *mapval;
> +	struct node_refcount_only *n, *m;
> +	int idx = 0;
> +
> +	mapval = bpf_map_lookup_elem(&stashed_refcount_only, &idx);
> +	if (!mapval)
> +		return 1;
> +
> +	bpf_rcu_read_lock();
> +	n = mapval->node;
> +	if (!n) {
> +		bpf_rcu_read_unlock();
> +		return 2;
> +	}
> +	m = bpf_refcount_acquire(n);
> +	bpf_rcu_read_unlock();

This isn't a bug, but since SEC("tc") programs are already treated as
being in an RCU critical section (in_rcu_cs() returns true for
non-sleepable programs), would a sleepable program type make the
bpf_rcu_read_lock()/unlock() section here actually load-bearing, or
could the pair simply be dropped?

> +
> +	if (!m)
> +		return 3;
> +	bpf_obj_drop(m);
> +
> +	return 0;
> +}
> +
>  static long __stash_map_empty_xchg(struct node_data *n, int idx)
>  {
>  	struct map_value *mapval = bpf_map_lookup_elem(&stashed_nodes, &idx);
> diff --git a/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c b/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c
> index 024ef2aae2008..acd3e81a39168 100644
> --- a/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c
> +++ b/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c

[ ... ]

> @@ -80,6 +96,37 @@ long refcount_acquire_maybe_null(void *ctx)
>  	return 0;
>  }
>
> +SEC("?tc")
> +__failure __msg("Possibly NULL pointer passed to trusted R1")
> +long refcount_acquire_rcu_map_kptr_unchecked_drop(void *ctx)
> +{
> +	struct map_value_refcount_only *mapval;
> +	struct node_refcount_only *tmp, *n, *m;
> +	int idx = 0;
> +
> +	tmp = bpf_obj_new(typeof(*tmp));
> +	if (!tmp)
> +		return 3;
> +	bpf_obj_drop(tmp);

This isn't a bug, but is the bpf_obj_new()/bpf_obj_drop() pair at the
start needed to force a complete BTF type for struct node_refcount_only,
or is it leftover setup? A one-line comment would keep someone from
removing it later.

> +
> +	mapval = bpf_map_lookup_elem(&stashed_refcount_only, &idx);
> +	if (!mapval)
> +		return 1;
> +
> +	bpf_rcu_read_lock();
> +	n = mapval->node;
> +	if (!n) {
> +		bpf_rcu_read_unlock();
> +		return 2;
> +	}
> +	m = bpf_refcount_acquire(n);
> +	bpf_rcu_read_unlock();
> +
> +	bpf_obj_drop(m);
> +
> +	return 0;
> +}
> +
>  SEC("?tc")
>  __failure __msg("Unreleased reference id=3 alloc_insn={{[0-9]+}}")
>  long rbtree_refcounted_node_ref_escapes_owning_input(void *ctx)

---

AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

In-Reply-To-Subject: selftests/bpf: Test refcount_acquire return nullability
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/31745514567

[kernel-patches-daemon-bpf]

Forwarding comment 5286983291 via email
In-Reply-To: 20260813211533.290256-4-dingning04@gmail.com
Patch: https://patchwork.kernel.org/project/netdevbpf/patch/20260813211533.290256-4-dingning04@gmail.com/

[kernel-patches-daemon-bpf]

Forwarding comment 5286997579 via email
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Patch: https://patchwork.kernel.org/project/netdevbpf/patch/20260813211533.290256-3-dingning04@gmail.com/

[kernel-patches-daemon-bpf]

Upstream branch: 4d9551b
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=1145728
version: 4

[kernel-patches-daemon-bpf]

Upstream branch: 409a9bd
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=1145728
version: 4

[kernel-patches-daemon-bpf]

Upstream branch: c7e6175
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=1145728
version: 4

[kernel-patches-daemon-bpf]

Upstream branch: d99bda7
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=1145728
version: 4

[kernel-patches-daemon-bpf]

Upstream branch: 34e0eb7
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=1145728
version: 4

[kernel-patches-daemon-bpf]

Upstream branch: 5fe7007
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=1145728
version: 4

[kernel-patches-daemon-bpf]

Upstream branch: 77877bf
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=1145728
version: 4

[kernel-patches-daemon-bpf]

Upstream branch: adb7719
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=1145728
version: 4

[kernel-patches-daemon-bpf]

Upstream branch: 6b0835a
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=1145728
version: 4

[kernel-patches-daemon-bpf]

Upstream branch: 6ab6a94
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=1145728
version: 4

Pull request is NOT updated. Failed to apply https://patchwork.kernel.org/project/netdevbpf/list/?series=1145728
error message:

Cmd('git') failed due to: exit code(128)
  cmdline: git am --3way
  stdout: 'Applying: bpf: Keep refcount_acquire nullable for borrowed RCU kptrs
Using index info to reconstruct a base tree...
M	kernel/bpf/verifier.c
Falling back to patching base and 3-way merge...
Auto-merging kernel/bpf/verifier.c
Applying: selftests/bpf: Test refcount_acquire return nullability
Using index info to reconstruct a base tree...
M	tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c
Falling back to patching base and 3-way merge...
Auto-merging tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c
CONFLICT (content): Merge conflict in tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c
Patch failed at 0002 selftests/bpf: Test refcount_acquire return nullability'
  stderr: 'error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"'

conflict:

diff --cc tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c
index eaaed0859f94,acd3e81a3916..000000000000
--- a/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c
+++ b/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c
@@@ -82,11 -97,34 +98,42 @@@ long refcount_acquire_maybe_null(void *
  }
  
  SEC("?tc")
++<<<<<<< HEAD
 +__failure __msg("R1 is neither owning or non-owning ref")
 +__msg("expects a pointer to a BPF-managed refcounted object, but R1 is a context pointer")
 +long refcount_acquire_non_object(void *ctx)
 +{
 +	return bpf_refcount_acquire(ctx) != NULL;
++=======
+ __failure __msg("Possibly NULL pointer passed to trusted R1")
+ long refcount_acquire_rcu_map_kptr_unchecked_drop(void *ctx)
+ {
+ 	struct map_value_refcount_only *mapval;
+ 	struct node_refcount_only *tmp, *n, *m;
+ 	int idx = 0;
+ 
+ 	tmp = bpf_obj_new(typeof(*tmp));
+ 	if (!tmp)
+ 		return 3;
+ 	bpf_obj_drop(tmp);
+ 
+ 	mapval = bpf_map_lookup_elem(&stashed_refcount_only, &idx);
+ 	if (!mapval)
+ 		return 1;
+ 
+ 	bpf_rcu_read_lock();
+ 	n = mapval->node;
+ 	if (!n) {
+ 		bpf_rcu_read_unlock();
+ 		return 2;
+ 	}
+ 	m = bpf_refcount_acquire(n);
+ 	bpf_rcu_read_unlock();
+ 
+ 	bpf_obj_drop(m);
+ 
+ 	return 0;
++>>>>>>> selftests/bpf: Test refcount_acquire return nullability
  }
  
  SEC("?tc")