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b=TM9584CoCVWiMFvcZyNQtjeivX2GDfDb6VcM7ie7sC1bRM16H4Aw3UyuMWq/Mi5aZ TvQIv1DaQXfV2Rzjrp6lHg5XVhv0UZf0WPxCpCvlwgxc53NBkeTeYUkWacRCo6tOtz iLz5AHcrgPwfhiKGztT9+tOBaD04R/bmyM5g7nRA= Date: Sat, 4 Jul 2026 17:49:53 -0700 From: Andrew Morton To: Sourav Panda Cc: muchun.song@linux.dev, osalvador@suse.de, david@kernel.org, surenb@google.com, fvdl@google.com, gthelen@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/hugetlb: Fix null nodemask in alloc_fresh_hugetlb_folio Message-Id: <20260704174953.002ee4990c62cec6bbfe4391@linux-foundation.org> In-Reply-To: <20260704174930.2885785-1-souravpanda@google.com> References: <20260704174930.2885785-1-souravpanda@google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: 4ctt6ncei69h4ajquqsbp3rxk5drhp9a X-Rspamd-Queue-Id: 184911C0007 X-Rspamd-Server: rspam01 X-Rspam-User: X-HE-Tag: 1783212595-14400 X-HE-Meta: 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 bH95mkKh S19c80ZIKDvjUH+BXFnZjvNqcxUf9QkwVeKFyjKOldnEXKaj75RXob2elATHiOmbQz/yfrt9/H86e2OByBbcta7FWk4FWuV7FvAsgNSkpg6ewmHfB4MUlzY/zxdSKBhilTbu45DUIR0fvpf9zDBpn6uFiAguLY8dAvA8IMUxHBJ4jaZOq6V3upDF7+Mqh45DHHjJ/XoKL4O2vb+nbslPEumawN40fLwNYxa27chQXmpJZqPza5TpYB1cibhOuGpMU5ol5i0wynecDsvaxz/czv+xkjIE5GIm3KttwU2SFgYGAMRN//sjiEIbH0toVHk4G7Up3jfUUAiTDHyFTNI4NyMRnLdrDBGeSrMX7zGVhkF4NMegy+28XmjrOqlPYtzvhWQKR Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, 4 Jul 2026 17:49:30 +0000 Sourav Panda wrote: > alloc_buddy_hugetlb_folio_with_mpol() can pass a NULL nodemask to > alloc_fresh_hugetlb_folio() as a fallback to allocate from all > nodes. If order is gigantic, alloc_fresh_hugetlb_folio() propagates > the NULL nodemask down to hugetlb_cma_alloc_frozen_folio() which blindly > dereferences it in for_each_node_mask(), leading to a null pointer > dereference. > > Similarly, if the CMA allocation fails, the fallback > alloc_contig_frozen_pages() is also called with a NULL nodemask, > which may cause issues. > > Fix this by explicitly checking if nodemask is NULL in > alloc_fresh_hugetlb_folio() and defaulting to > cpuset_current_mems_allowed. This ensures that both the CMA and > contiguous allocators receive a valid nodemask. > > Additionally, this patch adds a missing node_isset(nid, *nodemask) check > in hugetlb_cma_alloc_frozen_folio() to ensure the initial node allocation > attempt respects the memory policy. Thanks, bu the changelog still doesn't explain the userspace visible effects of the bug :( Important when proposing a cc:stable bugfix. So can you please condense and include the info you sent in reply to my v1 question? Also, Sashiko is saying stuff, as usual: https://sashiko.dev/#/patchset/20260704174930.2885785-1-souravpanda@google.com