Re: corrupted log causes infinite loop at mount

[David Chatterton <chatz@melbourne.sgi.com>]

Eric,

Eric Sandeen wrote:
> While playing with some filesystem corruption testers, I ran into this.
> 
> http://sandeen.net/xfs.31.img.bz2
> 
> If you try to mount, it gets into xfs_buf_get_noaddr via log replay with
> a len of 0, and I think this causes an infinite loop in the goto:
> 
>  try_again:
>         data = kmem_alloc(malloc_len, KM_SLEEP | KM_MAYFAIL);
>         if (unlikely(data == NULL))
>                 goto fail_free_buf;
> 
>         /* check whether alignment matches.. */
>         if ((__psunsigned_t)data !=
>             ((__psunsigned_t)data & ~target->bt_smask)) {
>                 /* .. else double the size and try again */
>                 kmem_free(data, malloc_len);
>                 malloc_len <<= 1;
>                 goto try_again;
>         }
> 
> Up the callchain a bit there is an ASSERT that the size is > 0, but of
> course that doesn't help on a non-debug kernel...
> 
> haven't had time to investigate beyond that.
> 
> -Eric
> 

I assume the loop is further up the chain since kmem_alloc should return NULL
when asked to alloc 0. So then the problem also lies further up the chain in
checking for a 0 length before calling down, and/or not assuming we are out of
memory when xfs_buf_get_noaddr fails.

David

-- 
David Chatterton
XFS Engineering Manager
SGI Australia