mm/mempolicy: fix sleeping allocation in alloc_pages_bulk_weighted_interleave()

Summary

In the Linux kernel, the following vulnerability has been resolved: mm/mempolicy: fix sleeping allocation in alloc_pages_bulk_weighted_interleave() syzbot reported a sleeping function called from invalid context splat in bucket_table_alloc(). When rhashtable_insert_slow() rehashes the table under rcu_read_lock(), it calls bucket_table_alloc(..., GFP_ATOMIC | __GFP_NOWARN). If the bucket table allocation uses vmalloc, __vmalloc_node_range_noprof() invokes vm_area_alloc_pages() -> alloc_pages_bulk_mempolicy_noprof() with the passed GFP_ATOMIC flags. If the current task has an MPOL_WEIGHTED_INTERLEAVE mempolicy, alloc_pages_bulk_weighted_interleave() is called and currently hardcodes GFP_KERNEL when allocating the temporary weights array, triggering a might_alloc() splat in atomic/RCU contexts. Pass the gfp flags (masked with GFP_RECLAIM_MASK to strip page-allocator zone modifiers like __GFP_HIGHMEM) received by alloc_pages_bulk_weighted_interleave() to kmalloc() instead of hardcoding GFP_KERNEL. Since the weights buffer is immediately initialized in full, kmalloc() is sufficient.

Timeline

1. Sep 16, 2026, 10:33 AM UTCCVE published
2. Oct 19, 2026, 8:56 AM UTCRecord last updated

Affected versions

• Linux Linux

  From fa3bea4e1f8202d787709b7e3654eb0a99aed758 · fixed in bcb3d0c867ee40dc48e9c085bf328fbc679b6656; From fa3bea4e1f8202d787709b7e3654eb0a99aed758 · fixed in 0ceda28f371df9e0bbdaa29214f71fe8298f23d8; From fa3bea4e1f8202d787709b7e3654eb0a99aed758 · fixed in 2943f1f4b7f2816177060eb9f551f2e6d8b629ba; From fa3bea4e1f8202d787709b7e3654eb0a99aed758 · fixed in 540e583b66d6402bf556fde5e53c817a54c1afe5

• Linux Linux

  6.9

• KernelLinux

  From 6.9.0 · fixed in 6.12.110; From 6.13.0 · fixed in 6.18.51; From 6.19.0 · fixed in 7.2.5

References 4