RE: [PATCH] block: create ioctl to discard-or-zeroout a range of blocks

From: Seymour, Shane M
Date: Thu Nov 12 2015 - 22:38:49 EST

> 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.

If you have someone trying to bypass your sanity checks then if start=18446744073709551104 and len=1024 the result of adding them together will be 512 (subtracting an extra 1 in the patched code to get 511 for end). That will pass the i_size_read check won't it? If so that would cause lstart in truncate_inode_pages_range() to be -512. I don't know what truncate_inode_pages_range() will do with a negative lstart value like that but it seems like an unusual value for your code to be willing to pass into truncate_inode_pages_range().

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