On Thu, Jun 30, 2016 at 12:34:48AM +0200, Vegard Nossum wrote:
> An extent with lblock = 4294967295 and len = 1 will pass the
> ext4_valid_extent() test:
>
> ext4_lblk_t last = lblock + len - 1;
>
> if (len == 0 || lblock > last)
> return 0;
>
> since last = 4294967295 + 1 - 1 = 4294967295. This would later trigger
> the BUG_ON(es->es_lblk + es->es_len < es->es_lblk) in ext4_es_end().
>
> We can simplify it by removing the - 1 altogether and changing the test
> to use lblock + len <= lblock, since now if len = 0, then lblock + 0 ==
> lblock and it fails, and if len > 0 then lblock + len > lblock in order
> to pass (i.e. it doesn't overflow).
>
> Fixes: 5946d0893 ("ext4: check for overlapping extents in ext4_valid_extent_entries()")
> Fixes: 2f974865f ("ext4: check for zero length extent explicitly")
> Cc: Eryu Guan <guaneryu@xxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Phil Turnbull <phil.turnbull@xxxxxxxxxx>
> Signed-off-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Thanks, applied.
- Ted
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