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2026 at 07:46:14PM +0900, Harry Yoo wrote: > When allocating slabobj_ext array in alloc_slab_obj_exts(), the array > can be allocated from the same slab we're allocating the array for. > This led to obj_exts_in_slab() incorrectly returning true [1], > although the array is not allocated from wasted space of the slab. > > Vlastimil Babka observed that this problem should be fixed even when > ignoring its incompatibility with obj_exts_in_slab(), because it creates > slabs that are never freed as there is always at least one allocated > object. > > To avoid this, use the next kmalloc size or large kmalloc when > kmalloc_slab() returns the same cache we're allocating the array for. > > In case of random kmalloc caches, there are multiple kmalloc caches for > the same size and the cache is selected based on the caller address. > Because it is fragile to ensure the same caller address is passed to > kmalloc_slab(), kmalloc_noprof(), and kmalloc_node_noprof(), fall back > to (s->object_size + 1) when the sizes are equal. > > Note that this doesn't happen when memory allocation profiling is > disabled, as when the allocation of the array is triggered by memory > cgroup (KMALLOC_CGROUP), the array is allocated from KMALLOC_NORMAL. > > Reported-by: kernel test robot > Closes: https://lore.kernel.org/oe-lkp/202601231457.f7b31e09-lkp@intel.com [1] > Cc: stable@vger.kernel.org > Fixes: 4b8736964640 ("mm/slab: add allocation accounting into slab allocation and free paths") > Signed-off-by: Harry Yoo > --- I don't think this is urgent enough to be fixed as part of -rcX, as it's been there since the introduction of memory allocation profiling. Perhaps it could be the first patch of slab/for-7.0/obj_metadata branch and -stable folks will pick up after it lands mainline?