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Thu, 28 May 2026 00:00:21 -0700 (PDT) Date: Thu, 28 May 2026 10:00:17 +0300 From: Dan Carpenter To: Lucas Faria Mendes Cc: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-staging@lists.linux.dev Subject: Re: [PATCH] vme_user: tighten slave window bounds and validate offsets Message-ID: References: <20260527211425.569038-1-lucas.fariamo08@gmail.com> 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=us-ascii Content-Disposition: inline In-Reply-To: <20260527211425.569038-1-lucas.fariamo08@gmail.com> On Wed, May 27, 2026 at 06:14:24PM -0300, Lucas Faria Mendes wrote: > Limit slave read/write operations to the allocated buffer size to > prevent out-of-bounds access when a slave window is > configured larger than its buffer. > Treat zero-sized windows and invalid file positions as errors, > and reject VME_SET_SLAVE requests that exceed the slave buffer. > This makes the user access driver more robust and avoids > silent EOF on invalid offsets. > > Signed-off-by: Lucas Faria Mendes No Fixes tag. This is a grab bag of changes. It needs to be split up into multiple changes. > > diff --git a/drivers/staging/vme_user/vme_user.c b/drivers/staging/vme_user/vme_user.c > index 11e25c2f6..ca65cb57c 100644 > --- a/drivers/staging/vme_user/vme_user.c > +++ b/drivers/staging/vme_user/vme_user.c > @@ -181,6 +181,7 @@ static ssize_t vme_user_read(struct file *file, char __user *buf, size_t count, > unsigned int minor = iminor(file_inode(file)); > ssize_t retval; > size_t image_size; > + size_t max_size; > > if (minor == CONTROL_MINOR) > return 0; > @@ -189,16 +190,24 @@ static ssize_t vme_user_read(struct file *file, char __user *buf, size_t count, > > /* XXX Do we *really* want this helper - we can use vme_*_get ? */ > image_size = vme_get_size(image[minor].resource); > + if (!image_size) { > + mutex_unlock(&image[minor].mutex); > + return -EINVAL; The original code looks pretty shady. Sure. This is fine. > + } > + > + max_size = image_size; > + if (type[minor] == SLAVE_MINOR && max_size > image[minor].size_buf) > + max_size = image[minor].size_buf; I don't understand this chunk. It seems unrelated to a zero return from vme_get_size(). It needs to be in a separate patch. > > /* Ensure we are starting at a valid location */ > - if ((*ppos < 0) || (*ppos > (image_size - 1))) { > + if ((*ppos < 0) || (*ppos >= max_size)) { Fine. The zero size - 1 is no good. > mutex_unlock(&image[minor].mutex); > - return 0; > + return -EINVAL; No. You can't change this because it's API. Also unrelated. > } > > /* Ensure not reading past end of the image */ > - if (*ppos + count > image_size) > - count = image_size - *ppos; > + if (*ppos + count > max_size) > + count = max_size - *ppos; This is unrelated to zero size so it would go in the other patch. > > switch (type[minor]) { > case MASTER_MINOR: > @@ -224,6 +233,7 @@ static ssize_t vme_user_write(struct file *file, const char __user *buf, > unsigned int minor = iminor(file_inode(file)); > ssize_t retval; > size_t image_size; > + size_t max_size; > > if (minor == CONTROL_MINOR) > return 0; > @@ -231,16 +241,24 @@ static ssize_t vme_user_write(struct file *file, const char __user *buf, > mutex_lock(&image[minor].mutex); > > image_size = vme_get_size(image[minor].resource); > + if (!image_size) { > + mutex_unlock(&image[minor].mutex); > + return -EINVAL; > + } > + > + max_size = image_size; > + if (type[minor] == SLAVE_MINOR && max_size > image[minor].size_buf) > + max_size = image[minor].size_buf; > > /* Ensure we are starting at a valid location */ > - if ((*ppos < 0) || (*ppos > (image_size - 1))) { > + if ((*ppos < 0) || (*ppos >= max_size)) { > mutex_unlock(&image[minor].mutex); > - return 0; > + return -EINVAL; > } > > /* Ensure not reading past end of the image */ > - if (*ppos + count > image_size) > - count = image_size - *ppos; > + if (*ppos + count > max_size) > + count = max_size - *ppos; > > switch (type[minor]) { > case MASTER_MINOR: Same review comments. > @@ -394,6 +412,9 @@ static int vme_user_ioctl(struct inode *inode, struct file *file, > return -EFAULT; > } > > + if (slave.size > image[minor].size_buf) > + return -EINVAL; This change is not explained well. It would need to be in it's own commit message. The size is supposed to be checked in vme_check_window() so this is the wrong place. I looked at the checking and it seems okay to me. The rest is just more of the same. regards, dan carpenter