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Wed, 07 Feb 2024 00:35:33 +0800 X-QQ-mid: xmsmtpt1707237333tgwzpj2kr Message-ID: X-QQ-XMAILINFO: NKv2G1wnhDBn0Qeh0KEAELRU5PYymkJtjrJl0x9WPh7uY2FwQzhHGIHIUWLC+F 9FTchisw4zfIsnJod27XT91951dwj1nw8gua0iYpm6z0susMJjdrMtjZZ380LYrjlX+wNkPNlwde TQTebx3ih0f7TTayCpVB7ENm9xf9Ki0WaEUxp7YRYSjQavgepJwA2JnHxoDAKDgk0eKPZ/JNqv9G CR7ShxvokbDpzgW+VokAJiZXd1nM8JovPS0kKNJpS5Z4Z/cSi7EhwYBAjH5am2NV3af9BtaCO66W Qi8N5E6gjB1esSulFhp2DI/hxozXirRN1mItweYx/XMhH+QWPFiiPWeck/wFORWpriUNw0vzYgG5 r5vcQemzDaAZ5bUW5Q0ae1rPpTXxyU+wi+Q1YF8+cB08622la1N3exP8lA+Am6jkBQ5+R8t1/zgt Yr4eVxROlPP9bimPPbxciyq2/pLLX8xJDKxervzmf9IIq1UDWQV/Kgw0ua9BuDqaldOL8MikkCQw x8Op2sQfD97ORuELvNyL95EdMAmfz5bKvCEJDeeH8Zh1agCqXhunlmfQbBHi2KjlrEHP7+s1jx+G 08K8b27J2cOqszbAYygspb1E3z+zQW2pNgtcr7k1hvjFAkbvCNN3T9bNd2R4m7jgSkIf9+6mzayT 0TSstqJusKSZ04oc3V6N1kI+4SZ5jhykzHX4wVRoVuxE5RP9hG9Xqa2IwFIv55Dx/7YJKLC5F5l5 im5iVya06TUKbVd44+DkEYyD8mUZV6Hnmha3A9n63ZR5LwTINrg5EMyzzka1kPS/WL2/2N0nAJ1r g+WjIT6jPeTiVi3Cb0lZPh2AB/Uxad7X3ePSmCd+I6BFX+qOUMyV6N3vm1pYpdG0U+geAvMXAziu 88jC5oa8XQRL+NAUsfUnciGliz+W5x+tP/SzPQ5q5ye2xudAAnriscZhHdUa9qSKypxtQcH/2njb gq2nVhigbnxNUSH8Rf1JhVyDRTUaVWmy4Kiflf9IarASsirh88Fi9BCsFzAfEgYCfyHn6lzFoWGj /JgsXFqZAMK1IX9+o6JTAu5hNlXCcHQ0lypBVY3w== X-QQ-XMRINFO: Nq+8W0+stu50PRdwbJxPCL0= From: wenyang.linux@foxmail.com To: Christian Brauner , Jens Axboe , Alexander Viro Cc: Wen Yang , Jan Kara , David Woodhouse , Matthew Wilcox , Eric Biggers , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] eventfd: strictly check the count parameter of eventfd_write to avoid inputting illegal strings Date: Wed, 7 Feb 2024 00:35:18 +0800 X-OQ-MSGID: <20240206163518.3811-1-wenyang.linux@foxmail.com> X-Mailer: git-send-email 2.25.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1790170230199334312 X-GMAIL-MSGID: 1790170230199334312 From: Wen Yang Since eventfd's document has clearly stated: A write(2) call adds the 8-byte integer value supplied in its buffer to the counter. However, in the current implementation, the following code snippet did not cause an error: char str[16] = "hello world"; uint64_t value; ssize_t size; int fd; fd = eventfd(0, 0); size = write(fd, &str, strlen(str)); printf("eventfd: test writing a string, size=%ld\n", size); size = read(fd, &value, sizeof(value)); printf("eventfd: test reading as uint64, size=%ld, valus=0x%lX\n", size, value); close(fd); And its output is: eventfd: test writing a string, size=8 eventfd: test reading as uint64, size=8, valus=0x6F77206F6C6C6568 By checking whether count is equal to sizeof(ucnt), such errors could be detected. It also follows the requirements of the manual. Signed-off-by: Wen Yang Cc: Alexander Viro Cc: Jens Axboe Cc: Christian Brauner Cc: Jan Kara Cc: David Woodhouse Cc: Matthew Wilcox Cc: Eric Biggers Cc: Cc: --- fs/eventfd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/eventfd.c b/fs/eventfd.c index fc4d81090763..9afdb722fa92 100644 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -251,7 +251,7 @@ static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t c ssize_t res; __u64 ucnt; - if (count < sizeof(ucnt)) + if (count != sizeof(ucnt)) return -EINVAL; if (copy_from_user(&ucnt, buf, sizeof(ucnt))) return -EFAULT;