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OUNy5UkrMZwS0VbWAtWM-qfHJfdzdHvr On Mon, Mar 09, 2026 at 04:22:19PM +0900, Harry Yoo wrote: > obj_exts_alloc_size() prevents recursive allocation of slabobj_ext > array from the same cache, to avoid creating slabs that are never freed. > > There is one mistake that returns the original size when memory > allocation profiling is disabled. The assumption was that > memcg-triggered slabobj_ext allocation is always served from > KMALLOC_CGROUP type. But this is wrong [1]: when the caller specifies > both __GFP_RECLAIMABLE and __GFP_ACCOUNT with SLUB_TINY enabled, the > allocation is served from normal kmalloc. This is because kmalloc_type() > prioritizes __GFP_RECLAIMABLE over __GFP_ACCOUNT, and SLUB_TINY aliases > KMALLOC_RECLAIM with KMALLOC_NORMAL. > > As a result, the recursion guard is bypassed and the problematic slabs > can be created. Fix this by removing the mem_alloc_profiling_enabled() > check entirely. The remaining is_kmalloc_normal() check is still > sufficient to detect whether the cache is of KMALLOC_NORMAL type and > avoid bumping the size if it's not. > > Without SLUB_TINY, no functional change intended. > With SLUB_TINY, allocations with __GFP_ACCOUNT|__GFP_RECLAIMABLE > now allocate a larger array if the sizes equal. > > Reported-by: Zw Tang > Fixes: 280ea9c3154b ("mm/slab: avoid allocating slabobj_ext array from its own slab") > Closes: https://lore.kernel.org/linux-mm/CAPHJ_VKuMKSke8b11AZQw1PTSFN4n2C0gFxC6xGOG0ZLHgPmnA@mail.gmail.com [1] > Cc: stable@vger.kernel.org > Signed-off-by: Harry Yoo > --- > > Zw Tang, could you please confirm that the warning disappears > on your test environment, with this patch applied? Oops, I think I saw Zw Tang's Tested-by: (thanks!), but appearently it's not sent to linux-mm. Could you please add your Tested-by: by replying to all, again? -- Cheers, Harry / Hyeonggon