[PATCH v3 34/35] crypto: Enable capability analysis

Marco Elver
2025-09-18T14:07:00Z

Enable capability analysis for crypto subsystem.

This demonstrates a larger conversion to use Clang's capability
analysis. The benefit is additional static checking of locking rules,
along with better documentation.

Note the use of the __acquire_ret macro how to define an API where a
function returns a pointer to an object (struct scomp_scratch) with a
lock held. Additionally, the analysis only resolves aliases where the
analysis unambiguously sees that a variable was not reassigned after
initialization, requiring minor code changes.

Signed-off-by: Marco Elver <elver@google.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: linux-crypto@vger.kernel.org
---
v3:
* Rebase - make use of __acquire_ret macro for new functions.
* Initialize variables once where we want the analysis to recognize aliases.

v2:
* New patch.
---
crypto/Makefile | 2 ++
crypto/acompress.c | 6 +++---
crypto/algapi.c | 2 ++
crypto/api.c | 1 +
crypto/crypto_engine.c | 2 +-
crypto/drbg.c | 5 +++++
crypto/internal.h | 2 +-
crypto/proc.c | 3 +++
crypto/scompress.c | 24 ++++++++++++------------
include/crypto/internal/acompress.h | 7 ++++---
include/crypto/internal/engine.h | 2 +-
11 files changed, 35 insertions(+), 21 deletions(-)

diff --git a/crypto/Makefile b/crypto/Makefile
index 6c5d59369dac..e73c50a54119 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -3,6 +3,8 @@
# Cryptographic API
#

+CAPABILITY_ANALYSIS := y
+
obj-$(CONFIG_CRYPTO) += crypto.o
crypto-y := api.o cipher.o

diff --git a/crypto/acompress.c b/crypto/acompress.c
index be28cbfd22e3..25df368df098 100644
--- a/crypto/acompress.c
+++ b/crypto/acompress.c
@@ -449,8 +449,8 @@ int crypto_acomp_alloc_streams(struct crypto_acomp_streams *s)
}
EXPORT_SYMBOL_GPL(crypto_acomp_alloc_streams);

-struct crypto_acomp_stream *crypto_acomp_lock_stream_bh(
- struct crypto_acomp_streams *s) __acquires(stream)
+struct crypto_acomp_stream *_crypto_acomp_lock_stream_bh(
+ struct crypto_acomp_streams *s)
{
struct crypto_acomp_stream __percpu *streams = s->streams;
int cpu = raw_smp_processor_id();
@@ -469,7 +469,7 @@ struct crypto_acomp_stream *crypto_acomp_lock_stream_bh(
spin_lock(&ps->lock);
return ps;
}
-EXPORT_SYMBOL_GPL(crypto_acomp_lock_stream_bh);
+EXPORT_SYMBOL_GPL(_crypto_acomp_lock_stream_bh);

void acomp_walk_done_src(struct acomp_walk *walk, int used)
{
diff --git a/crypto/algapi.c b/crypto/algapi.c
index e604d0d8b7b4..abc9333327d4 100644
--- a/crypto/algapi.c
+++ b/crypto/algapi.c
@@ -244,6 +244,7 @@ EXPORT_SYMBOL_GPL(crypto_remove_spawns);

static void crypto_alg_finish_registration(struct crypto_alg *alg,
struct list_head *algs_to_put)
+ __must_hold(&crypto_alg_sem)
{
struct crypto_alg *q;

@@ -299,6 +300,7 @@ static struct crypto_larval *crypto_alloc_test_larval(struct crypto_alg *alg)

static struct crypto_larval *
__crypto_register_alg(struct crypto_alg *alg, struct list_head *algs_to_put)
+ __must_hold(&crypto_alg_sem)
{
struct crypto_alg *q;
struct crypto_larval *larval;
diff --git a/crypto/api.c b/crypto/api.c
index 5724d62e9d07..05629644a688 100644
--- a/crypto/api.c
+++ b/crypto/api.c
@@ -57,6 +57,7 @@ EXPORT_SYMBOL_GPL(crypto_mod_put);

static struct crypto_alg *__crypto_alg_lookup(const char *name, u32 type,
u32 mask)
+ __must_hold_shared(&crypto_alg_sem)
{
struct crypto_alg *q, *alg = NULL;
int best = -2;
diff --git a/crypto/crypto_engine.c b/crypto/crypto_engine.c
index 18e1689efe12..1653a4bf5b31 100644
--- a/crypto/crypto_engine.c
+++ b/crypto/crypto_engine.c
@@ -453,8 +453,8 @@ struct crypto_engine *crypto_engine_alloc_init_and_set(struct device *dev,
snprintf(engine->name, sizeof(engine->name),
"%s-engine", dev_name(dev));

- crypto_init_queue(&engine->queue, qlen);
spin_lock_init(&engine->queue_lock);
+ crypto_init_queue(&engine->queue, qlen);

engine->kworker = kthread_run_worker(0, "%s", engine->name);
if (IS_ERR(engine->kworker)) {
diff --git a/crypto/drbg.c b/crypto/drbg.c
index dbe4c8bb5ceb..9684d952fdfd 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -231,6 +231,7 @@ static inline unsigned short drbg_sec_strength(drbg_flag_t flags)
*/
static int drbg_fips_continuous_test(struct drbg_state *drbg,
const unsigned char *entropy)
+ __must_hold(&drbg->drbg_mutex)
{
unsigned short entropylen = drbg_sec_strength(drbg->core->flags);
int ret = 0;
@@ -1061,6 +1062,7 @@ static inline int __drbg_seed(struct drbg_state *drbg, struct list_head *seed,
static inline int drbg_get_random_bytes(struct drbg_state *drbg,
unsigned char *entropy,
unsigned int entropylen)
+ __must_hold(&drbg->drbg_mutex)
{
int ret;

@@ -1075,6 +1077,7 @@ static inline int drbg_get_random_bytes(struct drbg_state *drbg,
}

static int drbg_seed_from_random(struct drbg_state *drbg)
+ __must_hold(&drbg->drbg_mutex)
{
struct drbg_string data;
LIST_HEAD(seedlist);
@@ -1132,6 +1135,7 @@ static bool drbg_nopr_reseed_interval_elapsed(struct drbg_state *drbg)
*/
static int drbg_seed(struct drbg_state *drbg, struct drbg_string *pers,
bool reseed)
+ __must_hold(&drbg->drbg_mutex)
{
int ret;
unsigned char entropy[((32 + 16) * 2)];
@@ -1368,6 +1372,7 @@ static inline int drbg_alloc_state(struct drbg_state *drbg)
static int drbg_generate(struct drbg_state *drbg,
unsigned char *buf, unsigned int buflen,
struct drbg_string *addtl)
+ __must_hold(&drbg->drbg_mutex)
{
int len = 0;
LIST_HEAD(addtllist);
diff --git a/crypto/internal.h b/crypto/internal.h
index b9afd68767c1..8fbe0226d48e 100644
--- a/crypto/internal.h
+++ b/crypto/internal.h
@@ -61,8 +61,8 @@ enum {
/* Maximum number of (rtattr) parameters for each template. */
#define CRYPTO_MAX_ATTRS 32

-extern struct list_head crypto_alg_list;
extern struct rw_semaphore crypto_alg_sem;
+extern struct list_head crypto_alg_list __guarded_by(&crypto_alg_sem);
extern struct blocking_notifier_head crypto_chain;

int alg_test(const char *driver, const char *alg, u32 type, u32 mask);
diff --git a/crypto/proc.c b/crypto/proc.c
index 82f15b967e85..5fb9fe86d023 100644
--- a/crypto/proc.c
+++ b/crypto/proc.c
@@ -19,17 +19,20 @@
#include "internal.h"

static void *c_start(struct seq_file *m, loff_t *pos)
+ __acquires_shared(&crypto_alg_sem)
{
down_read(&crypto_alg_sem);
return seq_list_start(&crypto_alg_list, *pos);
}

static void *c_next(struct seq_file *m, void *p, loff_t *pos)
+ __must_hold_shared(&crypto_alg_sem)
{
return seq_list_next(p, &crypto_alg_list, pos);
}

static void c_stop(struct seq_file *m, void *p)
+ __releases_shared(&crypto_alg_sem)
{
up_read(&crypto_alg_sem);
}
diff --git a/crypto/scompress.c b/crypto/scompress.c
index c651e7f2197a..fb87f3716426 100644
--- a/crypto/scompress.c
+++ b/crypto/scompress.c
@@ -28,8 +28,8 @@
struct scomp_scratch {
spinlock_t lock;
union {
- void *src;
- unsigned long saddr;
+ void *src __guarded_by(&lock);
+ unsigned long saddr __guarded_by(&lock);
};
};

@@ -38,8 +38,8 @@ static DEFINE_PER_CPU(struct scomp_scratch, scomp_scratch) = {
};

static const struct crypto_type crypto_scomp_type;
-static int scomp_scratch_users;
static DEFINE_MUTEX(scomp_lock);
+static int scomp_scratch_users __guarded_by(&scomp_lock);

static cpumask_t scomp_scratch_want;
static void scomp_scratch_workfn(struct work_struct *work);
@@ -67,6 +67,7 @@ static void crypto_scomp_show(struct seq_file *m, struct crypto_alg *alg)
}

static void crypto_scomp_free_scratches(void)
+ __capability_unsafe(/* frees @scratch */)
{
struct scomp_scratch *scratch;
int i;
@@ -101,7 +102,7 @@ static void scomp_scratch_workfn(struct work_struct *work)
struct scomp_scratch *scratch;

scratch = per_cpu_ptr(&scomp_scratch, cpu);
- if (scratch->src)
+ if (capability_unsafe(scratch->src))
continue;
if (scomp_alloc_scratch(scratch, cpu))
break;
@@ -111,6 +112,7 @@ static void scomp_scratch_workfn(struct work_struct *work)
}

static int crypto_scomp_alloc_scratches(void)
+ __capability_unsafe(/* allocates @scratch */)
{
unsigned int i = cpumask_first(cpu_possible_mask);
struct scomp_scratch *scratch;
@@ -139,7 +141,8 @@ static int crypto_scomp_init_tfm(struct crypto_tfm *tfm)
return ret;
}

-static struct scomp_scratch *scomp_lock_scratch(void) __acquires(scratch)
+#define scomp_lock_scratch(...) __acquire_ret(_scomp_lock_scratch(__VA_ARGS__), &__ret->lock)
+static struct scomp_scratch *_scomp_lock_scratch(void) __acquires_ret
{
int cpu = raw_smp_processor_id();
struct scomp_scratch *scratch;
@@ -159,7 +162,7 @@ static struct scomp_scratch *scomp_lock_scratch(void) __acquires(scratch)
}

static inline void scomp_unlock_scratch(struct scomp_scratch *scratch)
- __releases(scratch)
+ __releases(&scratch->lock)
{
spin_unlock(&scratch->lock);
}
@@ -171,8 +174,6 @@ static int scomp_acomp_comp_decomp(struct acomp_req *req, int dir)
bool src_isvirt = acomp_request_src_isvirt(req);
bool dst_isvirt = acomp_request_dst_isvirt(req);
struct crypto_scomp *scomp = *tfm_ctx;
- struct crypto_acomp_stream *stream;
- struct scomp_scratch *scratch;
unsigned int slen = req->slen;
unsigned int dlen = req->dlen;
struct page *spage, *dpage;
@@ -232,13 +233,12 @@ static int scomp_acomp_comp_decomp(struct acomp_req *req, int dir)
} while (0);
}

- stream = crypto_acomp_lock_stream_bh(&crypto_scomp_alg(scomp)->streams);
+ struct crypto_acomp_stream *stream = crypto_acomp_lock_stream_bh(&crypto_scomp_alg(scomp)->streams);

if (!src_isvirt && !src) {
- const u8 *src;
+ struct scomp_scratch *scratch = scomp_lock_scratch();
+ const u8 *src = scratch->src;

- scratch = scomp_lock_scratch();
- src = scratch->src;
memcpy_from_sglist(scratch->src, req->src, 0, slen);

if (dir)
diff --git a/include/crypto/internal/acompress.h b/include/crypto/internal/acompress.h
index 2d97440028ff..9a3f28baa804 100644
--- a/include/crypto/internal/acompress.h
+++ b/include/crypto/internal/acompress.h
@@ -191,11 +191,12 @@ static inline bool crypto_acomp_req_virt(struct crypto_acomp *tfm)
void crypto_acomp_free_streams(struct crypto_acomp_streams *s);
int crypto_acomp_alloc_streams(struct crypto_acomp_streams *s);

-struct crypto_acomp_stream *crypto_acomp_lock_stream_bh(
- struct crypto_acomp_streams *s) __acquires(stream);
+#define crypto_acomp_lock_stream_bh(...) __acquire_ret(_crypto_acomp_lock_stream_bh(__VA_ARGS__), &__ret->lock);
+struct crypto_acomp_stream *_crypto_acomp_lock_stream_bh(
+ struct crypto_acomp_streams *s) __acquires_ret;

static inline void crypto_acomp_unlock_stream_bh(
- struct crypto_acomp_stream *stream) __releases(stream)
+ struct crypto_acomp_stream *stream) __releases(&stream->lock)
{
spin_unlock_bh(&stream->lock);
}
diff --git a/include/crypto/internal/engine.h b/include/crypto/internal/engine.h
index f19ef376833f..6a1d27880615 100644
--- a/include/crypto/internal/engine.h
+++ b/include/crypto/internal/engine.h
@@ -45,7 +45,7 @@ struct crypto_engine {

struct list_head list;
spinlock_t queue_lock;
- struct crypto_queue queue;
+ struct crypto_queue queue __guarded_by(&queue_lock);
struct device *dev;

struct kthread_worker *kworker;
--
2.51.0.384.g4c02a37b29-goog