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Date: Sat, 15 May 2004 23:07:00 +0200 (CEST) From: Jirka Kosina <jikos@...os.cz> To: Michael Tokarev <mjt@....msk.ru> Cc: bugtraq@...urityfocus.com, full-disclosure@...ts.netsys.com Subject: Re: Re: Linux Kernel sctp_setsockopt() Integer Overflow On Sat, 15 May 2004, Michael Tokarev wrote: > But kmalloc(0) will return NULL, and the whole setsockopt > will finish with errno set to ENOMEM. > > From 2.4 mm/slab.c: > void * kmalloc (size_t size, int flags) > { > cache_sizes_t *csizep = cache_sizes; > > for (; csizep->cs_size; csizep++) { > if (size > csizep->cs_size) > continue; > return __kmem_cache_alloc(flags & GFP_DMA ? > csizep->cs_dmacachep : csizep->cs_cachep, flags); > } > return NULL; > } How did you come from the above snippet of the code to the idea that kmalloc(0) returns NULL? It allocates the number of bytes equal to the closest larger value of cache_sizes->cs_size entries ... so on typical system this would be something like 32 or 64 bytes, depending on the page size (see include/linux/kmalloc_sizes.h) ... and of course returns pointer to this data, which is definitely not NULL. -- JiKos. _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.netsys.com/full-disclosure-charter.html
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