From patchwork Sun Aug 4 07:56:15 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yafang Shao X-Patchwork-Id: 13752571 Received: from mail-oi1-f176.google.com (mail-oi1-f176.google.com [209.85.167.176]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A69BCEAC6; Sun, 4 Aug 2024 07:58:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.176 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722758285; cv=none; b=lyL+G+xipIn5hRi+pZQkeS9U0x0JM3Ix+u7Dk0jNZwnvGOYr1DYounSp1Cl/zOx78g09cZKqha86mSIpHcgmtSpNrfUt103+fMegvHXWy+HcFU2z4Y3/2rFTUMq2GB1hl8sjt38d/2OYHsX3K2YQ1nSqjdOFhPkRNmj18FD8G80= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722758285; c=relaxed/simple; bh=3Y0PjEqG6S3Uvz9FkBUvWOex8hIkmnI1AqczpSovQ98=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=GYcbtmGaLgMEfY85yuRkNFkkcWTi8YbHd2DSS1kGAGSSH7SApNZqiFOF++pPNHpm09/Alfb39XuTu/7lUKCVtQEkYpaFI84ihAKQviyhaH8QxyMcz4iDIa9xiLDzdDmUPRKusH6Kv8KxJDIMKiF3DzCx4Oeyy2poJBJWuZF3hhA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=ehA1WynY; arc=none smtp.client-ip=209.85.167.176 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ehA1WynY" Received: by mail-oi1-f176.google.com with SMTP id 5614622812f47-3db23a60850so5266164b6e.0; Sun, 04 Aug 2024 00:58:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1722758283; x=1723363083; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=FVkI7ws3sH8SytGBGHon98LlMkqoO/ooAo5HpqnjZFY=; b=ehA1WynYJNijz9rguNRGQul9+hEqRcKwGkUBi7G+SlH6Gxf1XY1ZMdc5ta0Mhe5eMo BoAFrcWqMcWJ0KxuMTP9VCeiQtgJ5SZSk219p/nVUD6ZAl5Qheud2bnNUupkFHukwmM+ tH/o6YLURm0/XJobTCp+epqf3nd/th/ExECHwsewel3Tp5Mchy14q1jaJOE57iVqJhe6 Aio7G62gdjjHRTwEsRtZg59DfC5tMQAThaiD4VbkUuAkWqr+nnw3MVMfHDFEs2mFosve mGRI1vaL31pzmZbq+s6Wevu2gWi5l4M7f1ZnCmom9UiCUP3lY67SeoOuBEd1lkoWLhaf UzPg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1722758283; x=1723363083; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=FVkI7ws3sH8SytGBGHon98LlMkqoO/ooAo5HpqnjZFY=; b=IxNMJa5ESY0k+MNEUvOEc8pW9oakpmA5EnGCUVlIfKHSAVoza+bOS33fH3VUknALuS MwwDnL3lA2kMUNeWblAmt1XG+/IItfXxCbrMimiD+8u+YoD80hB026aG4Ll4DYvWjNQH jfg5QZHGSFj/XO5sqOSdkZDQs1mFPFJ3cM2ff70esmAqsh/5zSVYAE0byKwYHMgfoYeV 24NCY+fSHTKcH0kUlgG7ww6XxyCgfSV3BNn+BRndacfdjoun1VUaEv3yJpBK/+ejD72k lqBXz+rzoUTnIjUIzV5Rjn3ub4mq6aFslfHVr2p0gj1q++u27w5IljHwQCiYTMc5VQsC zJaQ== X-Forwarded-Encrypted: i=1; AJvYcCXc2fvKDIMR4SQoIbSPRfC4Zx7iqUxPTfnKcM/3h9yXw6/gfzBhdiKkAuoEMpvtn0cLtACSw+2ocS4ttVXgvBnlEb04UM7FVjjXLDUHQIe8WRqAmHvpUz780le4sGJFJlUQ82srwKnjJn/Zzd4wPVZRZeYKANgSJ2vzWOuLLhYp0Y783N4Uk0mX76NRp13I/iAs+6VIq5EH8l5f6+Q082w9GKBRXArRyfLAR5IZi6ZSmOf/KqYG35jwM21BmLCbdcCFxoV/+hdxC8Lq9Dzogmt3bYpAyGNtYG7sin5K2n64NANXF1m5xnjRt2PldHKnuTQn2vALOA== X-Gm-Message-State: AOJu0YxkeOkQx/IiDkOtKfu9G1Q6ljUSS1RJ08Eas/F5HCGxTA5vUSR1 EJNO2zXLVt6TfDesF3aqcvODeMSqJ8hnwRMCkwvquMlrxklf0nR0 X-Google-Smtp-Source: AGHT+IGvj96nN6G8dNTQwO1gCnAi0LCFIOOEmeeyoUDneJo+nlGiP3jzVP2As4CYicNVTrPVKHFDvw== X-Received: by 2002:a05:6808:16ac:b0:3da:e587:3e1d with SMTP id 5614622812f47-3db557fc2cfmr11867023b6e.4.1722758282670; Sun, 04 Aug 2024 00:58:02 -0700 (PDT) Received: from localhost.localdomain ([39.144.105.172]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1ff59178248sm46387605ad.202.2024.08.04.00.57.50 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sun, 04 Aug 2024 00:58:02 -0700 (PDT) From: Yafang Shao To: akpm@linux-foundation.org Cc: torvalds@linux-foundation.org, ebiederm@xmission.com, alexei.starovoitov@gmail.com, rostedt@goodmis.org, catalin.marinas@arm.com, penguin-kernel@i-love.sakura.ne.jp, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, audit@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org, dri-devel@lists.freedesktop.org, Yafang Shao Subject: [PATCH v5 5/9] mm/util: Fix possible race condition in kstrdup() Date: Sun, 4 Aug 2024 15:56:15 +0800 Message-Id: <20240804075619.20804-6-laoar.shao@gmail.com> X-Mailer: git-send-email 2.30.1 (Apple Git-130) In-Reply-To: <20240804075619.20804-1-laoar.shao@gmail.com> References: <20240804075619.20804-1-laoar.shao@gmail.com> Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In kstrdup(), it is critical to ensure that the dest string is always NUL-terminated. However, potential race condidtion can occur between a writer and a reader. Consider the following scenario involving task->comm: reader writer len = strlen(s) + 1; strlcpy(tsk->comm, buf, sizeof(tsk->comm)); memcpy(buf, s, len); In this case, there is a race condition between the reader and the writer. The reader calculate the length of the string `s` based on the old value of task->comm. However, during the memcpy(), the string `s` might be updated by the writer to a new value of task->comm. If the new task->comm is larger than the old one, the `buf` might not be NUL-terminated. This can lead to undefined behavior and potential security vulnerabilities. Let's fix it by explicitly adding a NUL-terminator. Signed-off-by: Yafang Shao Cc: Andrew Morton --- mm/util.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/mm/util.c b/mm/util.c index 678c647b778f..912d64ede234 100644 --- a/mm/util.c +++ b/mm/util.c @@ -62,8 +62,14 @@ char *kstrdup(const char *s, gfp_t gfp) len = strlen(s) + 1; buf = kmalloc_track_caller(len, gfp); - if (buf) + if (buf) { memcpy(buf, s, len); + /* During memcpy(), the string might be updated to a new value, + * which could be longer than the string when strlen() is + * called. Therefore, we need to add a null termimator. + */ + buf[len - 1] = '\0'; + } return buf; } EXPORT_SYMBOL(kstrdup);