On Sun, Mar 22, 2020 at 8:11 AM Rohit Sarkar <rohitsarkar5398@xxxxxxxxx> wrote: > > On Sun, Mar 22, 2020 at 02:25:42AM +0200, Andy Shevchenko wrote: > > On Wed, Mar 18, 2020 at 08:25:22PM +0530, Rohit Sarkar wrote: > > > scnprintf returns the actual number of bytes written into the buffer as > > > opposed to snprintf which returns the number of bytes that would have > > > been written if the buffer was big enough. Using the output of snprintf > > > may lead to difficult to detect bugs. > > > > Nice. Have you investigate the code? > > > > > @@ -96,7 +96,7 @@ static ssize_t adis16136_show_serial(struct file *file, > > > if (ret) > > > return ret; > > > > > > - len = snprintf(buf, sizeof(buf), "%.4x%.4x%.4x-%.4x\n", lot1, lot2, > > > + len = scnprintf(buf, sizeof(buf), "%.4x%.4x%.4x-%.4x\n", lot1, lot2, > > > lot3, serial); > > > > > > return simple_read_from_buffer(userbuf, count, ppos, buf, len); > > > > The buffer size is 20, the pattern size I count to 19. Do you think snprintf() > > can fail? > That might be the case, but IMO using scnprintf can be considered as a > best practice. There is no overhead with this change and further if the > pattern is changed by someone in the future they might overlook the > buffersize If we cut the string above we will give wrong information to the user space. I think scnprintf() change is a noise and does not improve the situation anyhow. So, when anybody modifying such code the test should be performed. -- With Best Regards, Andy Shevchenko
