From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-171.mta0.migadu.com (out-171.mta0.migadu.com [91.218.175.171]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 98AA73438BF for ; Mon, 1 Jun 2026 21:43:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.171 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780350185; cv=none; b=j4ADvb3Q5owGTcnRKbyDPLPDshscc4IFrLq9o+2qIiT8weIVnCQjTL+Sv6F7BubcPehXBDTl5TI6lzoTGV4p66dJ5gLzx6C1D3/vj5ufisaa5OdhQJmr378zGaCtI/rwQC/K+pehzZ9nrL09VWbT1+CxcRBQGtM+qW3JumV+CZw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780350185; c=relaxed/simple; bh=vKC36Ha6Gml96K9KtWRfNbUPb1WRIRoZzsf2cx+lLlk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=cB6oqiiMYVbMyQGr7xfupcA2uP6YNuLq64exblexroUYSKidiT4qVqjesSopkKLszblTOns6Z9ndJnm/5qQFcs7HPWyGuj96teqY/+O6pt9mfwpNT1oYxJ1QmxTD3A3vkPr1fJ8pzp6Uy2rNow+SHn9IyJelVHQcI4zjxqIIdfI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=pwWujJDs; arc=none smtp.client-ip=91.218.175.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="pwWujJDs" Date: Mon, 1 Jun 2026 23:42:45 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780350171; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=KbRRQ6UrReGZ9CEz+b0Ya6nhw8Mi+MGNVxgZl4wtQvY=; b=pwWujJDscJ+QSlmOJpum5zso1mLfyH+KmNwql+rQJRpqJ+35ngOvk3Z9RaSaTH29CHYxOU MA4dHIg6zZdSRpHbEL+igqopQNyip9C4dFzFG0n1W+NtymSYJ9T5RQg9ZNPlmonJpG7DRT OhK+uv3GXcUOg4zzh8fpbOTkLU0T6mE= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Thorsten Blum To: Lothar Rubusch Cc: herbert@gondor.apana.org.au, davem@davemloft.net, nicolas.ferre@microchip.com, alexandre.belloni@bootlin.com, claudiu.beznea@tuxon.dev, tudor.ambarus@linaro.org, krzk+dt@kernel.org, linux-crypto@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] crypto: atmel-ecc - fix use after free situation Message-ID: References: <20260529092703.33086-1-l.rubusch@gmail.com> Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260529092703.33086-1-l.rubusch@gmail.com> X-Migadu-Flow: FLOW_OUT On Fri, May 29, 2026 at 09:27:03AM +0000, Lothar Rubusch wrote: > Fixes a possible race condition, when having multiple of such devices > attached (identified by sashiko feedback). > > The Scenario: > Thread A (Device 1 Probe): Successfully adds i2c_priv to the global > list (Line 324). The lock is released. > Thread B (An active crypto request): Concurrently calls > atmel_ecc_i2c_client_alloc(). It scans the global list, sees > Device 1, and assigns a crypto job to it. > Thread A: Moves to line 332. crypto_register_kpp() fails (e.g., out of > memory or name clash). > Thread A: Enters the error path. It removes Device 1 from the list and > frees the i2c_priv memory. > Thread B: Is still actively trying to talk to the I2C hardware using > the i2c_priv pointer it grabbed in Step 2. The memory is now > gone. Result: Kernel crash (Use-After-Free). > > Fixes: 11105693fa05 ("crypto: atmel-ecc - introduce Microchip / Atmel ECC driver") > Signed-off-by: Lothar Rubusch > --- > drivers/crypto/atmel-ecc.c | 10 ++++++++++ > drivers/crypto/atmel-i2c.h | 2 ++ > 2 files changed, 12 insertions(+) > > diff --git a/drivers/crypto/atmel-ecc.c b/drivers/crypto/atmel-ecc.c > index 0ca02995a1de..d391fe1462f6 100644 > --- a/drivers/crypto/atmel-ecc.c > +++ b/drivers/crypto/atmel-ecc.c > @@ -218,6 +218,8 @@ static struct i2c_client *atmel_ecc_i2c_client_alloc(void) > > list_for_each_entry(i2c_priv, &driver_data.i2c_client_list, > i2c_client_list_node) { > + if (!i2c_priv->ready) > + continue; > tfm_cnt = atomic_read(&i2c_priv->tfm_count); > if (tfm_cnt < min_tfm_cnt) { > min_tfm_cnt = tfm_cnt; > @@ -322,20 +324,24 @@ static int atmel_ecc_probe(struct i2c_client *client) > return ret; > > i2c_priv = i2c_get_clientdata(client); > + i2c_priv->ready = false; > > spin_lock(&driver_data.i2c_list_lock); > list_add_tail(&i2c_priv->i2c_client_list_node, > &driver_data.i2c_client_list); > + i2c_priv->ready = true; > spin_unlock(&driver_data.i2c_list_lock); > > ret = crypto_register_kpp(&atmel_ecdh_nist_p256); > if (ret) { > spin_lock(&driver_data.i2c_list_lock); > + i2c_priv->ready = false; > list_del(&i2c_priv->i2c_client_list_node); > spin_unlock(&driver_data.i2c_list_lock); > > dev_err(&client->dev, "%s alg registration failed\n", > atmel_ecdh_nist_p256.base.cra_driver_name); > + return ret; > } else { > dev_info(&client->dev, "atmel ecc algorithms registered in /proc/crypto\n"); > } > @@ -347,6 +353,10 @@ static void atmel_ecc_remove(struct i2c_client *client) > { > struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client); > > + spin_lock(&driver_data.i2c_list_lock); > + i2c_priv->ready = false; > + spin_unlock(&driver_data.i2c_list_lock); > + > /* Return EBUSY if i2c client already allocated. */ > if (atomic_read(&i2c_priv->tfm_count)) { > /* > diff --git a/drivers/crypto/atmel-i2c.h b/drivers/crypto/atmel-i2c.h > index 72f04c15682f..e3b12030f9c4 100644 > --- a/drivers/crypto/atmel-i2c.h > +++ b/drivers/crypto/atmel-i2c.h > @@ -129,6 +129,7 @@ struct atmel_ecc_driver_data { > * @wake_token_sz : size in bytes of the wake_token > * @tfm_count : number of active crypto transformations on i2c client > * @hwrng : hold the hardware generated rng > + * @ready : hw client is ready to use > * > * Reads and writes from/to the i2c client are sequential. The first byte > * transmitted to the device is treated as the byte size. Any attempt to send > @@ -145,6 +146,7 @@ struct atmel_i2c_client_priv { > size_t wake_token_sz; > atomic_t tfm_count ____cacheline_aligned; > struct hwrng hwrng; > + bool ready; > }; I don't think the ready flag fixes the race. A concurrent tfm can still bind to the shared I2C client after atmel_ecc_probe() adds it to the global list and marks it as ready, but before crypto_register_kpp() fails. Thanks, Thorsten