+ mm-mempolicy-fix-sleeping-allocation-in-alloc_pages_bulk_weighted_interleave.patch added to mm-hotfixes-unstable branch

The patch titled
     Subject: mm/mempolicy: fix sleeping allocation in alloc_pages_bulk_weighted_interleave()
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-mempolicy-fix-sleeping-allocation-in-alloc_pages_bulk_weighted_interleave.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mempolicy-fix-sleeping-allocation-in-alloc_pages_bulk_weighted_interleave.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Eric Dumazet <[email protected]>
Subject: mm/mempolicy: fix sleeping allocation in alloc_pages_bulk_weighted_interleave()
Date: Fri, 21 Aug 2026 17:04:07 +0000

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.

Link: https://lore.kernel.org/[email protected]
Fixes: fa3bea4e1f82 ("mm/mempolicy: introduce MPOL_WEIGHTED_INTERLEAVE for weighted interleaving")
Signed-off-by: Eric Dumazet <[email protected]>
Reported-by: [email protected]
Closes: https://lore.kernel.org/lkml/[email protected]/T/#u
Reviewed-by: Andrew Morton <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: Byungchul Park <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Gregory Price <[email protected]>
Cc: "Huang, Ying" <[email protected]>
Cc: Joshua Hahn <[email protected]>
Cc: Matthew Brost <[email protected]>
Cc: Rakie Kim <[email protected]>
Cc: Zi Yan <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---

 mm/mempolicy.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/mempolicy.c~mm-mempolicy-fix-sleeping-allocation-in-alloc_pages_bulk_weighted_interleave
+++ a/mm/mempolicy.c
@@ -2683,7 +2683,7 @@ static unsigned long alloc_pages_bulk_we
 	prev_node = node;
 
 	/* create a local copy of node weights to operate on outside rcu */
-	weights = kzalloc(nr_node_ids, GFP_KERNEL);
+	weights = kmalloc(nr_node_ids, gfp & GFP_RECLAIM_MASK);
 	if (!weights)
 		return total_allocated;
 
_

Patches currently in -mm which might be from [email protected] are

mm-mempolicy-fix-sleeping-allocation-in-alloc_pages_bulk_weighted_interleave.patch