From mboxrd@z Thu Jan 1 00:00:00 1970 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 1BF103A8F3; Wed, 15 Nov 2023 19:52:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="NrZXF8cg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BD90AC433C9; Wed, 15 Nov 2023 19:52:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1700077951; bh=DqVbYuSNPmY8Fn6zZg8Lxb9JEGIBcwZW/odk8MwwSzo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NrZXF8cgY4+ugN+B52vzYTA55nGbfWd0Ycc+awVRyboBOF/8sIrsNOj6Gm+PZcXH9 zMZNq4gRnr5ETmWQ32q1FW3dNfBAQOgY8pRfJCbRkb3wJh+/48GLO443oPSi4xEMaS WsA7g0T+bTTc2VB2HglzhegzQm+hUZNo6oP9bplw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Arnd Bergmann , Andy Shevchenko , linux-hardening@vger.kernel.org, Kees Cook , Sasha Levin Subject: [PATCH 6.1 018/379] string: Adjust strtomem() logic to allow for smaller sources Date: Wed, 15 Nov 2023 14:21:33 -0500 Message-ID: <20231115192646.235811582@linuxfoundation.org> X-Mailer: git-send-email 2.42.1 In-Reply-To: <20231115192645.143643130@linuxfoundation.org> References: <20231115192645.143643130@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kees Cook [ Upstream commit 0e108725f6cc5b3be9e607f89c9fbcbb236367b7 ] Arnd noticed we have a case where a shorter source string is being copied into a destination byte array, but this results in a strnlen() call that exceeds the size of the source. This is seen with -Wstringop-overread: In file included from ../include/linux/uuid.h:11, from ../include/linux/mod_devicetable.h:14, from ../include/linux/cpufeature.h:12, from ../arch/x86/coco/tdx/tdx.c:7: ../arch/x86/coco/tdx/tdx.c: In function 'tdx_panic.constprop': ../include/linux/string.h:284:9: error: 'strnlen' specified bound 64 exceeds source size 60 [-Werror=stringop-overread] 284 | memcpy_and_pad(dest, _dest_len, src, strnlen(src, _dest_len), pad); \ | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ../arch/x86/coco/tdx/tdx.c:124:9: note: in expansion of macro 'strtomem_pad' 124 | strtomem_pad(message.str, msg, '\0'); | ^~~~~~~~~~~~ Use the smaller of the two buffer sizes when calling strnlen(). When src length is unknown (SIZE_MAX), it is adjusted to use dest length, which is what the original code did. Reported-by: Arnd Bergmann Fixes: dfbafa70bde2 ("string: Introduce strtomem() and strtomem_pad()") Tested-by: Arnd Bergmann Cc: Andy Shevchenko Cc: linux-hardening@vger.kernel.org Signed-off-by: Kees Cook Signed-off-by: Sasha Levin --- include/linux/string.h | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/include/linux/string.h b/include/linux/string.h index cf7607b321027..26ab8928d8661 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -276,10 +276,12 @@ void memcpy_and_pad(void *dest, size_t dest_len, const void *src, size_t count, */ #define strtomem_pad(dest, src, pad) do { \ const size_t _dest_len = __builtin_object_size(dest, 1); \ + const size_t _src_len = __builtin_object_size(src, 1); \ \ BUILD_BUG_ON(!__builtin_constant_p(_dest_len) || \ _dest_len == (size_t)-1); \ - memcpy_and_pad(dest, _dest_len, src, strnlen(src, _dest_len), pad); \ + memcpy_and_pad(dest, _dest_len, src, \ + strnlen(src, min(_src_len, _dest_len)), pad); \ } while (0) /** @@ -297,10 +299,11 @@ void memcpy_and_pad(void *dest, size_t dest_len, const void *src, size_t count, */ #define strtomem(dest, src) do { \ const size_t _dest_len = __builtin_object_size(dest, 1); \ + const size_t _src_len = __builtin_object_size(src, 1); \ \ BUILD_BUG_ON(!__builtin_constant_p(_dest_len) || \ _dest_len == (size_t)-1); \ - memcpy(dest, src, min(_dest_len, strnlen(src, _dest_len))); \ + memcpy(dest, src, strnlen(src, min(_src_len, _dest_len))); \ } while (0) /** -- 2.42.0