From nobody Tue Apr 7 19:55:53 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 53B7B2989B5; Wed, 11 Mar 2026 23:06:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773270409; cv=none; b=bYH2KggxlKFJILdfJPhDTPyzF5Xd/JzxtUaxH3Ues+ZGbq90yHE5bst5tRucaVnMDPazAKr0s/Rl+h4RLsHRskYRPoNB+DD79wdqB21eQDjQ5JJEiRs5HJtOpiKtXtMjQ6nKAdonHBPZ+8kgnjwIHmeqMFZGBEme6DUN8GzaM8M= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773270409; c=relaxed/simple; bh=nyCis1OKm867BGk54vBM7sp6aWigeD6z3A7a10n9BmE=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=r4oN3QTh/Id5jt3F5s1FWw0ZtcZRqM16Zp4QvhSgWDxWFp/nTuU+pzL51oaDfT8QsAoPlXim9wn1NGDFtQKV3PzK0ZiXk+cqBwm3/vUvFzY1duzF021+eGIbJV14TrqN/IqCEglnqHBWl1vQN4EkCoedsdrXjEYyYOaEecr0aGs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=e7toUs4c; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="e7toUs4c" Received: by smtp.kernel.org (Postfix) with ESMTPS id 08809C4CEF7; Wed, 11 Mar 2026 23:06:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773270409; bh=nyCis1OKm867BGk54vBM7sp6aWigeD6z3A7a10n9BmE=; h=From:Date:Subject:To:Cc:Reply-To:From; b=e7toUs4csjuJvgq8ohVhWy2bPVlGDCSRO259nEFgNVZ1/9uqjD9y3wgKD04BjJY/i QE1hm/ZVTTzuHAET2qz39vbW/lSmCjfLyd6PcACpAVGaS9AEuB1j9o8yEmd3jN7Ty/ u5MYYRaOmiK7Yp0+9ArjptzSLS6l7dtbpW4gmxcI923CTSCFLXQyhmgLxpjciPnFM5 cIvcezSWV2tT7gq7s4MQX2hYLsORJaeC8KNHpxuTDyR8NkxGpHONDU3UXohLM0SqDb 7N9UInXOe6Oyj7Wp+jgXbXecf1e0mr1rdFRrtMCW8NGsLhzBarxvum+qgZABFuNFQA lILvH2aLKh/tw== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id EC4DD103E2F1; Wed, 11 Mar 2026 23:06:48 +0000 (UTC) From: =?utf-8?q?Bence_Cs=C3=B3k=C3=A1s_via_B4_Relay?= Date: Thu, 12 Mar 2026 00:06:35 +0100 Subject: [PATCH] USB: core: Use `krealloc()` in `usb_cache_string()` Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260312-usb-krealloc-v1-1-f76b92b92402@sch.bme.hu> X-B4-Tracking: v=1; b=H4sIAAAAAAAC/x3MwQqDMAyA4VeRnBewrQzcq8gOaZfOMFclURmI7 75ux+/w/wcYq7DBrTlAeReTuVS4SwNppPJklEc1+NZf2+AcbhbxpUzTNCfsuHMh+9BTn6Emi3K Wz3833KsjGWNUKmn8Td5kKyuc5xcU/ug4dwAAAA== X-Change-ID: 20260311-usb-krealloc-4e413f239a9f To: Greg Kroah-Hartman Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, =?utf-8?q?Bence_Cs=C3=B3k=C3=A1s?= X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1773270407; l=1845; i=bence98@sch.bme.hu; s=20260213; h=from:subject:message-id; bh=ryeZKOW7CoNcTvHQhdlplcN1pMIWzqbmCO+DbTrOUHo=; b=TQXh95Qshna5DUlvdb+3cekUBsb7EGBbjdiOEEpRVdGjKu6uCnWEJ6F4M+n8xqlupNwBMgqIk uDLpQEFx+8DAwBBrbkN3uqDNpMaYsnT+UqcAEygIWIgk9Vtrtj9nuHU X-Developer-Key: i=bence98@sch.bme.hu; a=ed25519; pk=rtWE8PtqZ5ZMyUVCckDq8i1ASLxgUbV2fwDA8KaOli8= X-Endpoint-Received: by B4 Relay for bence98@sch.bme.hu/20260213 with auth_id=636 X-Original-From: =?utf-8?q?Bence_Cs=C3=B3k=C3=A1s?= Reply-To: bence98@sch.bme.hu From: Bence Cs=C3=B3k=C3=A1s Instead of "shrinking" the allocation by `kmalloc()`ing a new, smaller buffer, utilize `krealloc()` to shrink the existing allocation. This saves a `memcpy()`, as well as guards against `smallbuf` allocation failure. Signed-off-by: Bence Cs=C3=B3k=C3=A1s --- Using `krealloc()` makes this code from 2005 more readable as well as robust. Nested `if`s were also unrolled. --- drivers/usb/core/message.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c index ea970ddf8879..dfe61d8b913b 100644 --- a/drivers/usb/core/message.c +++ b/drivers/usb/core/message.c @@ -1005,7 +1005,7 @@ int usb_string(struct usb_device *dev, int index, cha= r *buf, size_t size) } EXPORT_SYMBOL_GPL(usb_string); =20 -/* one UTF-8-encoded 16-bit character has at most three bytes */ +/* one 16-bit character, when UTF-8-encoded, has at most three bytes */ #define MAX_USB_STRING_SIZE (127 * 3 + 1) =20 /** @@ -1026,17 +1026,17 @@ char *usb_cache_string(struct usb_device *udev, int= index) return NULL; =20 buf =3D kmalloc(MAX_USB_STRING_SIZE, GFP_NOIO); - if (buf) { - len =3D usb_string(udev, index, buf, MAX_USB_STRING_SIZE); - if (len > 0) { - smallbuf =3D kmalloc(++len, GFP_NOIO); - if (!smallbuf) - return buf; - memcpy(smallbuf, buf, len); - } + if (!buf) + return NULL; + + len =3D usb_string(udev, index, buf, MAX_USB_STRING_SIZE); + if (len <=3D 0) { kfree(buf); + return NULL; } - return smallbuf; + + smallbuf =3D krealloc(buf, len + 1, GFP_NOIO); + return smallbuf ? : buf; } EXPORT_SYMBOL_GPL(usb_cache_string); =20 --- base-commit: 80234b5ab240f52fa45d201e899e207b9265ef91 change-id: 20260311-usb-krealloc-4e413f239a9f Best regards, --=20 Bence Cs=C3=B3k=C3=A1s