[PATCH] xfs: catch invalid negative blknos in _xfs_buf_find()

[Eric Sandeen]

On 11/19/14 4:12 PM, Eric Sandeen wrote:
> Here blkno is a daddr_t, which is a __s64; it's possible to hold
> a value which is negative, and thus pass the (blkno >= eofs)
> test.  Then we try to do a xfs_perag_get() for a ridiculous
> agno via xfs_daddr_to_agno(), and bad things happen when that
> fails, and returns a null pag which is dereferenced shortly
> thereafter.
> 
> Found via a user-supplied fuzzed image...

NAK - this needs a bit more love; if we catch this and fail,
the caller may still do something crazy with this data.

V2 coming in a bit.

-Eric