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Thu, 23 Apr 2026 03:44:02 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface MIME-Version: 1.0 Date: Thu, 23 Apr 2026 09:43:42 +0200 From: "Ard Biesheuvel" To: "Lothar Rubusch" , "Herbert Xu" , "Thorsten Blum" , davem@davemloft.net, nicolas.ferre@microchip.com, alexandre.belloni@bootlin.com, claudiu.beznea@tuxon.dev, "Linus Walleij" Cc: linux-crypto@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Message-Id: <81feaa5f-3f66-40f0-be83-d6efcb6271bf@app.fastmail.com> In-Reply-To: <20260422210936.20095-2-l.rubusch@gmail.com> References: <20260422210936.20095-1-l.rubusch@gmail.com> <20260422210936.20095-2-l.rubusch@gmail.com> Subject: Re: [PATCH v3 1/3] crypto: atmel-sha204a - fix memory leak at non-blocking RNG work_data Content-Type: text/plain Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260423_004405_417143_34774897 X-CRM114-Status: GOOD ( 23.89 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Lothar, On Wed, 22 Apr 2026, at 23:09, Lothar Rubusch wrote: > The driver allocated memory for work_data in the non-blocking read > path but never free'd it again. After first read-out the memory pointer > seemed to be recycled and never was allocated again, due to some errors > in the logic, so that the leak was not growing. > Why can't we just reuse the work_data, instead of alloc/freeing it every time? > Add kfree(work_data) in the completion callback on error. then add > kfree(work_data) after the data is consumed in the subsequent read > call. Finally ensure atomic_dec() is called only after the data has > been consumed or an error occurred to prevent race conditions. > > Fixes: da001fb651b0 ("crypto: atmel-i2c - add support for SHA204A > random number generator") > Signed-off-by: Lothar Rubusch > --- > drivers/crypto/atmel-sha204a.c | 43 ++++++++++++++++++++-------------- > 1 file changed, 26 insertions(+), 17 deletions(-) > > diff --git a/drivers/crypto/atmel-sha204a.c > b/drivers/crypto/atmel-sha204a.c > index dbb39ed0cea1..19720bdd446d 100644 > --- a/drivers/crypto/atmel-sha204a.c > +++ b/drivers/crypto/atmel-sha204a.c > @@ -25,13 +25,17 @@ static void atmel_sha204a_rng_done(struct > atmel_i2c_work_data *work_data, > struct atmel_i2c_client_priv *i2c_priv = work_data->ctx; > struct hwrng *rng = areq; > > - if (status) > + if (status) { > dev_warn_ratelimited(&i2c_priv->client->dev, > "i2c transaction failed (%d)\n", > status); > + kfree(work_data); > + rng->priv = 0; > + atomic_dec(&i2c_priv->tfm_count); > + return; > + } > > rng->priv = (unsigned long)work_data; > - atomic_dec(&i2c_priv->tfm_count); > } > > static int atmel_sha204a_rng_read_nonblocking(struct hwrng *rng, void > *data, > @@ -42,31 +46,36 @@ static int > atmel_sha204a_rng_read_nonblocking(struct hwrng *rng, void *data, > > i2c_priv = container_of(rng, struct atmel_i2c_client_priv, hwrng); > > - /* keep maximum 1 asynchronous read in flight at any time */ > - if (!atomic_add_unless(&i2c_priv->tfm_count, 1, 1)) > - return 0; > - > + /* Verify if data available from last run */ > if (rng->priv) { > work_data = (struct atmel_i2c_work_data *)rng->priv; > max = min(sizeof(work_data->cmd.data), max); > memcpy(data, &work_data->cmd.data, max); > - rng->priv = 0; > - } else { > - work_data = kmalloc_obj(*work_data, GFP_ATOMIC); > - if (!work_data) { > - atomic_dec(&i2c_priv->tfm_count); > - return -ENOMEM; > - } > - work_data->ctx = i2c_priv; > - work_data->client = i2c_priv->client; > > - max = 0; > + /* Now, free memory */ > + kfree(work_data); > + rng->priv = 0; > + atomic_dec(&i2c_priv->tfm_count); > + return max; > } > > + /* When a request is still in-flight but not processed */ > + if (atomic_read(&i2c_priv->tfm_count) > 0) > + return 0; > + > + /* Start a new request */ > + work_data = kmalloc_obj(*work_data, GFP_ATOMIC); > + if (!work_data) > + return -ENOMEM; > + > + atomic_inc(&i2c_priv->tfm_count); > + work_data->ctx = i2c_priv; > + work_data->client = i2c_priv->client; > + > atmel_i2c_init_random_cmd(&work_data->cmd); > atmel_i2c_enqueue(work_data, atmel_sha204a_rng_done, rng); > > - return max; > + return 0; > } > > static int atmel_sha204a_rng_read(struct hwrng *rng, void *data, size_t max, > -- > 2.53.0