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SubjectRe: [PATCH][2/2] fix unchecked returns from kmalloc() (in mm/slab.c)
On Tue, Dec 07 2004, Jesper Juhl wrote:
>
> Problem reported by Katrina Tsipenyuk and the Fortify Software engineering
> team in thread with subject "PROBLEM: unchecked returns from kmalloc() in
> linux-2.6.10-rc2".
>
> Unfortunately I'm not very familliar with the code in question, and since
> I didn't find a really good way to deal with a failing kmalloc() here I
> settled for second best which is to add a BUG_ON() in case kmalloc fails.
> This will at least crash in a sane way at the point the problem occoures
> rather than getting strange problems at a (possibly) later time. If
> someone who's familliar with how this code works has a better solution
> then please step forward :) but in the mean time I think this is at least
> a slight improvement over the current situation.
>
> Patch has been compile tested and boot tested and didn't blow up
> instantly, but please review before applying.
>
>
> Signed-off-by: Jesper Juhl <juhl-lkml@dif.dk>
>
> diff -up linux-2.6.10-rc3-bk2-orig/mm/slab.c linux-2.6.10-rc3-bk2/mm/slab.c
> --- linux-2.6.10-rc3-bk2-orig/mm/slab.c 2004-12-06 22:24:56.000000000 +0100
> +++ linux-2.6.10-rc3-bk2/mm/slab.c 2004-12-07 21:27:20.000000000 +0100
> @@ -804,6 +804,7 @@ void __init kmem_cache_init(void)
> void * ptr;
>
> ptr = kmalloc(sizeof(struct arraycache_init), GFP_KERNEL);
> + BUG_ON(ptr == NULL); /* FIXME: Can a failed kmalloc be handled better? */
> local_irq_disable();
> BUG_ON(ac_data(&cache_cache) != &initarray_cache.cache);
> memcpy(ptr, ac_data(&cache_cache), sizeof(struct arraycache_init));

This is pointless, as a NULL deref on memcpy will give you the exact
same info.

--
Jens Axboe

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