bpf: fix key serial argument of bpf_lookup_user_key()

bpf: fix key serial argument of bpf_lookup_user_key()

[James Bottomley]

The underlying lookup_user_key() function uses a signed 32 bit integer
for key serial numbers because legitimate serial numbers are positive
(and > 3) and keyrings are negative.  Using a u32 for the keyring in
the bpf function doesn't currently cause any conversion problems but
will start to trip the signed to unsigned conversion warnings when the
kernel enables them, so convert the argument to signed (and update the
tests accordingly) before it acquires more users.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 kernel/trace/bpf_trace.c                                  | 2 +-
 tools/testing/selftests/bpf/bpf_kfuncs.h                  | 2 +-
 tools/testing/selftests/bpf/progs/rcu_read_lock.c         | 5 +++--
 tools/testing/selftests/bpf/progs/test_lookup_key.c       | 4 ++--
 tools/testing/selftests/bpf/progs/test_sig_in_xattr.c     | 2 +-
 tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c | 2 +-
 tools/testing/selftests/bpf/progs/verifier_ref_tracking.c | 2 +-
 7 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 132c8be6f635..0a06ea6638fe 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1270,7 +1270,7 @@ __bpf_kfunc_start_defs();
  * Return: a bpf_key pointer with a valid key pointer if the key is found, a
  *         NULL pointer otherwise.
  */
-__bpf_kfunc struct bpf_key *bpf_lookup_user_key(u32 serial, u64 flags)
+__bpf_kfunc struct bpf_key *bpf_lookup_user_key(s32 serial, u64 flags)
 {
 	key_ref_t key_ref;
 	struct bpf_key *bkey;
diff --git a/tools/testing/selftests/bpf/bpf_kfuncs.h b/tools/testing/selftests/bpf/bpf_kfuncs.h
index 8215c9b3115e..9386dfe8b884 100644
--- a/tools/testing/selftests/bpf/bpf_kfuncs.h
+++ b/tools/testing/selftests/bpf/bpf_kfuncs.h
@@ -69,7 +69,7 @@ extern int bpf_get_file_xattr(struct file *file, const char *name,
 			      struct bpf_dynptr *value_ptr) __ksym;
 extern int bpf_get_fsverity_digest(struct file *file, struct bpf_dynptr *digest_ptr) __ksym;
 
-extern struct bpf_key *bpf_lookup_user_key(__u32 serial, __u64 flags) __ksym;
+extern struct bpf_key *bpf_lookup_user_key(__s32 serial, __u64 flags) __ksym;
 extern struct bpf_key *bpf_lookup_system_key(__u64 id) __ksym;
 extern void bpf_key_put(struct bpf_key *key) __ksym;
 extern int bpf_verify_pkcs7_signature(struct bpf_dynptr *data_ptr,
diff --git a/tools/testing/selftests/bpf/progs/rcu_read_lock.c b/tools/testing/selftests/bpf/progs/rcu_read_lock.c
index 43637ee2cdcd..3a868a199349 100644
--- a/tools/testing/selftests/bpf/progs/rcu_read_lock.c
+++ b/tools/testing/selftests/bpf/progs/rcu_read_lock.c
@@ -16,10 +16,11 @@ struct {
 	__type(value, long);
 } map_a SEC(".maps");
 
-__u32 user_data, key_serial, target_pid;
+__u32 user_data, target_pid;
+__s32 key_serial;
 __u64 flags, task_storage_val, cgroup_id;
 
-struct bpf_key *bpf_lookup_user_key(__u32 serial, __u64 flags) __ksym;
+struct bpf_key *bpf_lookup_user_key(__s32 serial, __u64 flags) __ksym;
 void bpf_key_put(struct bpf_key *key) __ksym;
 void bpf_rcu_read_lock(void) __ksym;
 void bpf_rcu_read_unlock(void) __ksym;
diff --git a/tools/testing/selftests/bpf/progs/test_lookup_key.c b/tools/testing/selftests/bpf/progs/test_lookup_key.c
index cdbbb12f1491..1f7e1e59b073 100644
--- a/tools/testing/selftests/bpf/progs/test_lookup_key.c
+++ b/tools/testing/selftests/bpf/progs/test_lookup_key.c
@@ -14,11 +14,11 @@
 char _license[] SEC("license") = "GPL";
 
 __u32 monitored_pid;
-__u32 key_serial;
+__s32 key_serial;
 __u32 key_id;
 __u64 flags;
 
-extern struct bpf_key *bpf_lookup_user_key(__u32 serial, __u64 flags) __ksym;
+extern struct bpf_key *bpf_lookup_user_key(__s32 serial, __u64 flags) __ksym;
 extern struct bpf_key *bpf_lookup_system_key(__u64 id) __ksym;
 extern void bpf_key_put(struct bpf_key *key) __ksym;
 
diff --git a/tools/testing/selftests/bpf/progs/test_sig_in_xattr.c b/tools/testing/selftests/bpf/progs/test_sig_in_xattr.c
index 8ef6b39335b6..34b30e2603f0 100644
--- a/tools/testing/selftests/bpf/progs/test_sig_in_xattr.c
+++ b/tools/testing/selftests/bpf/progs/test_sig_in_xattr.c
@@ -40,7 +40,7 @@ char digest[MAGIC_SIZE + SIZEOF_STRUCT_FSVERITY_DIGEST + SHA256_DIGEST_SIZE];
 __u32 monitored_pid;
 char sig[MAX_SIG_SIZE];
 __u32 sig_size;
-__u32 user_keyring_serial;
+__s32 user_keyring_serial;
 
 SEC("lsm.s/file_open")
 int BPF_PROG(test_file_open, struct file *f)
diff --git a/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c b/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c
index e96d09e11115..ff8d755548b9 100644
--- a/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c
+++ b/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c
@@ -17,7 +17,7 @@
 #define MAX_SIG_SIZE 1024
 
 __u32 monitored_pid;
-__u32 user_keyring_serial;
+__s32 user_keyring_serial;
 __u64 system_keyring_id;
 
 struct data {
diff --git a/tools/testing/selftests/bpf/progs/verifier_ref_tracking.c b/tools/testing/selftests/bpf/progs/verifier_ref_tracking.c
index 683a882b3e6d..910365201f68 100644
--- a/tools/testing/selftests/bpf/progs/verifier_ref_tracking.c
+++ b/tools/testing/selftests/bpf/progs/verifier_ref_tracking.c
@@ -27,7 +27,7 @@ struct bpf_key {} __attribute__((preserve_access_index));
 
 extern void bpf_key_put(struct bpf_key *key) __ksym;
 extern struct bpf_key *bpf_lookup_system_key(__u64 id) __ksym;
-extern struct bpf_key *bpf_lookup_user_key(__u32 serial, __u64 flags) __ksym;
+extern struct bpf_key *bpf_lookup_user_key(__s32 serial, __u64 flags) __ksym;
 
 /* BTF FUNC records are not generated for kfuncs referenced
  * from inline assembly. These records are necessary for
-- 
2.43.0

Re: bpf: fix key serial argument of bpf_lookup_user_key()

[Roberto Sassu]

On Tue, 2025-06-17 at 10:57 -0400, James Bottomley wrote:
> The underlying lookup_user_key() function uses a signed 32 bit integer
> for key serial numbers because legitimate serial numbers are positive
> (and > 3) and keyrings are negative.  Using a u32 for the keyring in
> the bpf function doesn't currently cause any conversion problems but
> will start to trip the signed to unsigned conversion warnings when the
> kernel enables them, so convert the argument to signed (and update the
> tests accordingly) before it acquires more users.
> 
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

Looks good from my side:

Reviewed-by: Roberto Sassu <roberto.sassu@huawei.com>

Thanks

Roberto

> ---
>  kernel/trace/bpf_trace.c                                  | 2 +-
>  tools/testing/selftests/bpf/bpf_kfuncs.h                  | 2 +-
>  tools/testing/selftests/bpf/progs/rcu_read_lock.c         | 5 +++--
>  tools/testing/selftests/bpf/progs/test_lookup_key.c       | 4 ++--
>  tools/testing/selftests/bpf/progs/test_sig_in_xattr.c     | 2 +-
>  tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c | 2 +-
>  tools/testing/selftests/bpf/progs/verifier_ref_tracking.c | 2 +-
>  7 files changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 132c8be6f635..0a06ea6638fe 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -1270,7 +1270,7 @@ __bpf_kfunc_start_defs();
>   * Return: a bpf_key pointer with a valid key pointer if the key is found, a
>   *         NULL pointer otherwise.
>   */
> -__bpf_kfunc struct bpf_key *bpf_lookup_user_key(u32 serial, u64 flags)
> +__bpf_kfunc struct bpf_key *bpf_lookup_user_key(s32 serial, u64 flags)
>  {
>  	key_ref_t key_ref;
>  	struct bpf_key *bkey;
> diff --git a/tools/testing/selftests/bpf/bpf_kfuncs.h b/tools/testing/selftests/bpf/bpf_kfuncs.h
> index 8215c9b3115e..9386dfe8b884 100644
> --- a/tools/testing/selftests/bpf/bpf_kfuncs.h
> +++ b/tools/testing/selftests/bpf/bpf_kfuncs.h
> @@ -69,7 +69,7 @@ extern int bpf_get_file_xattr(struct file *file, const char *name,
>  			      struct bpf_dynptr *value_ptr) __ksym;
>  extern int bpf_get_fsverity_digest(struct file *file, struct bpf_dynptr *digest_ptr) __ksym;
>  
> -extern struct bpf_key *bpf_lookup_user_key(__u32 serial, __u64 flags) __ksym;
> +extern struct bpf_key *bpf_lookup_user_key(__s32 serial, __u64 flags) __ksym;
>  extern struct bpf_key *bpf_lookup_system_key(__u64 id) __ksym;
>  extern void bpf_key_put(struct bpf_key *key) __ksym;
>  extern int bpf_verify_pkcs7_signature(struct bpf_dynptr *data_ptr,
> diff --git a/tools/testing/selftests/bpf/progs/rcu_read_lock.c b/tools/testing/selftests/bpf/progs/rcu_read_lock.c
> index 43637ee2cdcd..3a868a199349 100644
> --- a/tools/testing/selftests/bpf/progs/rcu_read_lock.c
> +++ b/tools/testing/selftests/bpf/progs/rcu_read_lock.c
> @@ -16,10 +16,11 @@ struct {
>  	__type(value, long);
>  } map_a SEC(".maps");
>  
> -__u32 user_data, key_serial, target_pid;
> +__u32 user_data, target_pid;
> +__s32 key_serial;
>  __u64 flags, task_storage_val, cgroup_id;
>  
> -struct bpf_key *bpf_lookup_user_key(__u32 serial, __u64 flags) __ksym;
> +struct bpf_key *bpf_lookup_user_key(__s32 serial, __u64 flags) __ksym;
>  void bpf_key_put(struct bpf_key *key) __ksym;
>  void bpf_rcu_read_lock(void) __ksym;
>  void bpf_rcu_read_unlock(void) __ksym;
> diff --git a/tools/testing/selftests/bpf/progs/test_lookup_key.c b/tools/testing/selftests/bpf/progs/test_lookup_key.c
> index cdbbb12f1491..1f7e1e59b073 100644
> --- a/tools/testing/selftests/bpf/progs/test_lookup_key.c
> +++ b/tools/testing/selftests/bpf/progs/test_lookup_key.c
> @@ -14,11 +14,11 @@
>  char _license[] SEC("license") = "GPL";
>  
>  __u32 monitored_pid;
> -__u32 key_serial;
> +__s32 key_serial;
>  __u32 key_id;
>  __u64 flags;
>  
> -extern struct bpf_key *bpf_lookup_user_key(__u32 serial, __u64 flags) __ksym;
> +extern struct bpf_key *bpf_lookup_user_key(__s32 serial, __u64 flags) __ksym;
>  extern struct bpf_key *bpf_lookup_system_key(__u64 id) __ksym;
>  extern void bpf_key_put(struct bpf_key *key) __ksym;
>  
> diff --git a/tools/testing/selftests/bpf/progs/test_sig_in_xattr.c b/tools/testing/selftests/bpf/progs/test_sig_in_xattr.c
> index 8ef6b39335b6..34b30e2603f0 100644
> --- a/tools/testing/selftests/bpf/progs/test_sig_in_xattr.c
> +++ b/tools/testing/selftests/bpf/progs/test_sig_in_xattr.c
> @@ -40,7 +40,7 @@ char digest[MAGIC_SIZE + SIZEOF_STRUCT_FSVERITY_DIGEST + SHA256_DIGEST_SIZE];
>  __u32 monitored_pid;
>  char sig[MAX_SIG_SIZE];
>  __u32 sig_size;
> -__u32 user_keyring_serial;
> +__s32 user_keyring_serial;
>  
>  SEC("lsm.s/file_open")
>  int BPF_PROG(test_file_open, struct file *f)
> diff --git a/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c b/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c
> index e96d09e11115..ff8d755548b9 100644
> --- a/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c
> +++ b/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c
> @@ -17,7 +17,7 @@
>  #define MAX_SIG_SIZE 1024
>  
>  __u32 monitored_pid;
> -__u32 user_keyring_serial;
> +__s32 user_keyring_serial;
>  __u64 system_keyring_id;
>  
>  struct data {
> diff --git a/tools/testing/selftests/bpf/progs/verifier_ref_tracking.c b/tools/testing/selftests/bpf/progs/verifier_ref_tracking.c
> index 683a882b3e6d..910365201f68 100644
> --- a/tools/testing/selftests/bpf/progs/verifier_ref_tracking.c
> +++ b/tools/testing/selftests/bpf/progs/verifier_ref_tracking.c
> @@ -27,7 +27,7 @@ struct bpf_key {} __attribute__((preserve_access_index));
>  
>  extern void bpf_key_put(struct bpf_key *key) __ksym;
>  extern struct bpf_key *bpf_lookup_system_key(__u64 id) __ksym;
> -extern struct bpf_key *bpf_lookup_user_key(__u32 serial, __u64 flags) __ksym;
> +extern struct bpf_key *bpf_lookup_user_key(__s32 serial, __u64 flags) __ksym;
>  
>  /* BTF FUNC records are not generated for kfuncs referenced
>   * from inline assembly. These records are necessary for

Re: bpf: fix key serial argument of bpf_lookup_user_key()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Tue, 17 Jun 2025 10:57:36 -0400 you wrote:
> The underlying lookup_user_key() function uses a signed 32 bit integer
> for key serial numbers because legitimate serial numbers are positive
> (and > 3) and keyrings are negative.  Using a u32 for the keyring in
> the bpf function doesn't currently cause any conversion problems but
> will start to trip the signed to unsigned conversion warnings when the
> kernel enables them, so convert the argument to signed (and update the
> tests accordingly) before it acquires more users.
> 
> [...]

Here is the summary with links:
  - bpf: fix key serial argument of bpf_lookup_user_key()
    https://git.kernel.org/bpf/bpf-next/c/bd07bd12f2c1

You are awesome, thank you!
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