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DKIM_TRACE(0.00)[suse.cz:+] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Flag: NO X-Spam-Level: On 10/14/24 14:52, Feng Tang wrote: > On Mon, Oct 14, 2024 at 10:53:32AM +0200, Vlastimil Babka wrote: >> On 10/14/24 09:52, Feng Tang wrote: >> > On Fri, Oct 04, 2024 at 05:52:10PM +0800, Vlastimil Babka wrote: >> > Thanks for the suggestion! >> > >> > As there were error report about the NULL slab for big kmalloc object, how >> > about the following code for >> > >> > __do_krealloc(const void *p, size_t new_size, gfp_t flags) >> > { >> > void *ret; >> > size_t ks = 0; >> > int orig_size = 0; >> > struct kmem_cache *s = NULL; >> > >> > /* Check for double-free. */ >> > if (likely(!ZERO_OR_NULL_PTR(p))) { >> > if (!kasan_check_byte(p)) >> > return NULL; >> > >> > ks = ksize(p); >> >> I think this will result in __ksize() doing >> skip_orig_size_check(folio_slab(folio)->slab_cache, object); >> and we don't want that? > > I think that's fine. As later code will re-set the orig_size anyway. But you also read it first. >> > /* Some objects have no orig_size, like big kmalloc case */ >> > if (is_kfence_address(p)) { >> > orig_size = kfence_ksize(p); >> > } else if (virt_to_slab(p)) { >> > s = virt_to_cache(p); >> > orig_size = get_orig_size(s, (void *)p); here. >> > } >> Also the checks below repeat some of the checks of ksize(). > > Yes, there is some redundancy, mostly the virt_to_slab() > >> So I think in __do_krealloc() we should do things manually to determine ks >> and not call ksize(). Just not break any of the cases ksize() handles >> (kfence, large kmalloc). > > OK, originally I tried not to expose internals of __ksize(). Let me > try this way. ksize() makes assumptions that a user outside of slab itself is calling it. But we (well mostly Kees) also introduced kmalloc_size_roundup() to avoid querying ksize() for the purposes of writing beyond the original kmalloc(size) up to the bucket size. So maybe we can also investigate if the skip_orig_size_check() mechanism can be removed now? Still I think __do_krealloc() should rather do its own thing and not call ksize(). > Thanks, > Feng > >> >> > >> > } else { >> > goto alloc_new; >> > } >> > >> > /* If the object doesn't fit, allocate a bigger one */ >> > if (new_size > ks) >> > goto alloc_new; >> > >> > /* Zero out spare memory. */ >> > if (want_init_on_alloc(flags)) { >> > kasan_disable_current(); >> > if (orig_size && orig_size < new_size) >> > memset((void *)p + orig_size, 0, new_size - orig_size); >> > else >> > memset((void *)p + new_size, 0, ks - new_size); >> > kasan_enable_current(); >> > } >> > >> > /* Setup kmalloc redzone when needed */ >> > if (s && slub_debug_orig_size(s) && !is_kfence_address(p)) { >> > set_orig_size(s, (void *)p, new_size); >> > if (s->flags & SLAB_RED_ZONE && new_size < ks) >> > memset_no_sanitize_memory((void *)p + new_size, >> > SLUB_RED_ACTIVE, ks - new_size); >> > } >> > >> > p = kasan_krealloc((void *)p, new_size, flags); >> > return (void *)p; >> > >> > alloc_new: >> > ret = kmalloc_node_track_caller_noprof(new_size, flags, NUMA_NO_NODE, _RET_IP_); >> > if (ret && p) { >> > /* Disable KASAN checks as the object's redzone is accessed. */ >> > kasan_disable_current(); >> > memcpy(ret, kasan_reset_tag(p), orig_size ?: ks); >> > kasan_enable_current(); >> > } >> > >> > return ret; >> > }