On Wed, Nov 11, 2015 at 05:30:07AM +0000, Seymour, Shane M wrote: > A quick question about this part of the patch: > > > + uint64_t end = start + len - 1; > > > + if (end >= i_size_read(bdev->bd_inode)) > return -EINVAL; > > > + /* Invalidate the page cache, including dirty pages */ > > + mapping = bdev->bd_inode->i_mapping; > > + truncate_inode_pages_range(mapping, start, end); > > blk_ioctl_zeroout accepts unsigned values for start and end (uint64_t) but > loff_t types are turned from i_size_read() and passed as the 2nd and 3rd > values to truncate_inode_pages_range() and loff_t is a signed value. It > should be possible to pass in some values would overflow the calculation of > end causing the test on the value of end and the result of i_size_read to > pass but then end up passing a large unsigned value for in start that would > be implicitly converted to signed in truncate_inode_pages_range. I was > wondering if you'd tested passing in data that would cause sign conversion > issues when passed into truncate_inode_pages_range (does it handle it > gracefully?) or should this code: > > if (start & 511) > return -EINVAL; > if (len & 511) > return -EINVAL; > > be something more like this (for better sanity checking of your arguments) > which will ensure that you don't have implicit conversion issues from > unsigned to signed and ensure that the result of adding them together won't > either: > > if ((start & 511) || (start > (uint64_t)LLONG_MAX)) > return -EINVAL; > if ((len & 511) ) || (len > (uint64_t)LLONG_MAX)) > return -EINVAL; > if (end > (uint64_t)LLONG_MAX) > return -EINVAL; > > My apologies in advance if I've made a mistake when looking at this and my > concerns about unsigned values being implicitly converted to signed are > unfounded (I would have hoped for compiler warnings about any implicit > conversions though). I don't have a device large enough to test for signedness errors, since passing huge values for start and len never make it past the i_size_read check. However, I do see that I forgot to check the padding values, so I'll update that. --D > > Thanks > Shane -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
