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Donenfeld" , LKML References: From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/19/22 9:01 PM, Al Viro wrote: > On Thu, May 19, 2022 at 05:43:15PM -0600, Jens Axboe wrote: > >> -static int write_pool(const char __user *ubuf, size_t len) >> +static size_t write_pool(struct iov_iter *iter) >> { >> size_t block_len; >> int ret = 0; >> >> - while (len) { >> - block_len = min(len, sizeof(block)); >> - if (copy_from_user(block, ubuf, block_len)) { >> - ret = -EFAULT; >> + while (iov_iter_count(iter)) { >> + block_len = min(iov_iter_count(iter), sizeof(block)); >> + if (!copy_from_iter(block, block_len, iter)) { >> + if (!ret) >> + ret = -EFAULT; >> goto out; >> } > > Feed it a buffer with only 1 byte mapped, watch it'll pass to mix_pool_bytes(). > And see how much of 'block' has been used uninitialized... I don't follow? Buffer with 1 byte, iter setup with 1 byte. We copy 1 byte, and we pass 1 byte to mix_pool_bytes(). What am I missing? > And why bother with that min thing, anyway? > > ssize_t ret = 0; > > while (iov_iter_count(iter)) { > u8 block[BLAKE2S_BLOCK_SIZE]; > size_t copied = copy_from_iter(block, sizeof(block), iter); > if (!copied) { > if (!ret) > ret = -EFAULT; > break; > } > mix_pool_bytes(block, copied); > ret += copied; > } > return ret; > > and be done with that... Agree, that does look better, the min() part could've been killed with the conversion indeed. >> @@ -1382,11 +1378,16 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) >> return -EINVAL; >> if (get_user(size, p++)) >> return -EFAULT; >> - retval = write_pool((const char __user *)p, size); >> + >> + iov.iov_base = p; >> + iov.iov_len = size; >> + iov_iter_init(&iter, WRITE, &iov, 1, size); > > That'd be > import_single_range(WRITE, p, size, &iov, &iter); Yep that'd be a simpler equivalent. -- Jens Axboe