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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id af79cd13be357-9372ea69aa0sm392753685a.4.2026.08.21.10.40.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Aug 2026 10:40:05 -0700 (PDT) Date: Fri, 21 Aug 2026 13:40:03 -0400 From: Gregory Price To: Eric Dumazet Cc: Andrew Morton , linux-kernel , syzbot+0dbf6d295b3350944f0b@syzkaller.appspotmail.com, David Hildenbrand , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Ying Huang , Alistair Popple , linux-mm@kvack.org Subject: Re: [PATCH] mm/mempolicy: Fix sleeping allocation in alloc_pages_bulk_weighted_interleave() Message-ID: References: <20260821170407.3721004-1-edumazet@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260821170407.3721004-1-edumazet@google.com> X-Stat-Signature: e78woenqo3ef1nz6m1xjyo9tuwcr9t4s X-Rspamd-Queue-Id: C9DE414000E X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1787334006-826088 X-HE-Meta: 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 50MnUmNP 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Aug 21, 2026 at 05:04:07PM +0000, Eric Dumazet wrote: > 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. > > Fixes: fa3bea4e1f82 ("mm/mempolicy: introduce MPOL_WEIGHTED_INTERLEAVE for weighted interleaving") > Reported-by: syzbot+0dbf6d295b3350944f0b@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/lkml/6a88837e.ae6ddae5.3da009.0040.GAE@google.com/T/#u > Signed-off-by: Eric Dumazet Yup, seems a solid oversight on my part. Reviewed-by: Gregory Price (Meta) ~Gregory