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 8831AE57D for ; Sun, 9 Jul 2023 15:16:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 25FA6C433C8; Sun, 9 Jul 2023 15:16:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1688915798; bh=BmgDoqmmR/0aTtaSlsk8FtTiOkTJEmegsMp0yEKSxUg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ho3gRI3z9J6GKrt221Go42+ut1AIgMuBIiwZ8Yimz2KEpo3AKab1eTc5qOynk3q6t 6Vf3ooN9dpsLlPioDoLI00eK4MjbSdeHfDFNZ1eGJatKakN6GXFxqfAeiG/0ioie+A Wl8uWoLSNHJWaw5wZTcudaX+BQn2o16OlmPCuDlOgB1YoM89ZzQasIXZv1TXGpQT5/ DuVAs1Pscy93DqjpOEnodEJRQWghL8AVMlzlMyAl1HyyvAVoDOCA/C91YzD3iRfUjk 5Ih+rES+vkp++Ea0XQzxSUq0I5axqOjujBxQAdPixxCKZZzISeAD6+XL+O+0n1N8FP +SWnBIvOw3MFA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Gustavo A. R. Silva" , Simon Horman , Johannes Berg , Sasha Levin , johannes@sipsolutions.net, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, linux-wireless@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 3/5] wifi: wext-core: Fix -Wstringop-overflow warning in ioctl_standard_iw_point() Date: Sun, 9 Jul 2023 11:16:28 -0400 Message-Id: <20230709151632.514098-3-sashal@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230709151632.514098-1-sashal@kernel.org> References: <20230709151632.514098-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 4.19.288 Content-Transfer-Encoding: 8bit From: "Gustavo A. R. Silva" [ Upstream commit 71e7552c90db2a2767f5c17c7ec72296b0d92061 ] -Wstringop-overflow is legitimately warning us about extra_size pontentially being zero at some point, hence potenially ending up _allocating_ zero bytes of memory for extra pointer and then trying to access such object in a call to copy_from_user(). Fix this by adding a sanity check to ensure we never end up trying to allocate zero bytes of data for extra pointer, before continue executing the rest of the code in the function. Address the following -Wstringop-overflow warning seen when built m68k architecture with allyesconfig configuration: from net/wireless/wext-core.c:11: In function '_copy_from_user', inlined from 'copy_from_user' at include/linux/uaccess.h:183:7, inlined from 'ioctl_standard_iw_point' at net/wireless/wext-core.c:825:7: arch/m68k/include/asm/string.h:48:25: warning: '__builtin_memset' writing 1 or more bytes into a region of size 0 overflows the destination [-Wstringop-overflow=] 48 | #define memset(d, c, n) __builtin_memset(d, c, n) | ^~~~~~~~~~~~~~~~~~~~~~~~~ include/linux/uaccess.h:153:17: note: in expansion of macro 'memset' 153 | memset(to + (n - res), 0, res); | ^~~~~~ In function 'kmalloc', inlined from 'kzalloc' at include/linux/slab.h:694:9, inlined from 'ioctl_standard_iw_point' at net/wireless/wext-core.c:819:10: include/linux/slab.h:577:16: note: at offset 1 into destination object of size 0 allocated by '__kmalloc' 577 | return __kmalloc(size, flags); | ^~~~~~~~~~~~~~~~~~~~~~ This help with the ongoing efforts to globally enable -Wstringop-overflow. Link: https://github.com/KSPP/linux/issues/315 Signed-off-by: Gustavo A. R. Silva Reviewed-by: Simon Horman Link: https://lore.kernel.org/r/ZItSlzvIpjdjNfd8@work Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin --- net/wireless/wext-core.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/wireless/wext-core.c b/net/wireless/wext-core.c index 76a80a41615be..a57f54bc0e1a7 100644 --- a/net/wireless/wext-core.c +++ b/net/wireless/wext-core.c @@ -796,6 +796,12 @@ static int ioctl_standard_iw_point(struct iw_point *iwp, unsigned int cmd, } } + /* Sanity-check to ensure we never end up _allocating_ zero + * bytes of data for extra. + */ + if (extra_size <= 0) + return -EFAULT; + /* kzalloc() ensures NULL-termination for essid_compat. */ extra = kzalloc(extra_size, GFP_KERNEL); if (!extra) -- 2.39.2