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b=ILY5LQrhTZ3NtMNZSWgVDs+k5D6opsKq+ZzeOYdZs0+O/k5H2CR4JN8dpnL8IjU1c hv96auK1r1xc8LiMr48nGjIncVoimPM+MEHwQGHy+1a9E/jLckoRX9Zg0RpjwVG+p6 xP1kZaUUVnxwPSCQ91f702WP62xx9vsWg9mEESV5VQ8MVAmcKmbIL0+FIC9W1NMkpP peKWbGcEAaF01iveYHcOUH7aPaHE8ABlMr6qlagfHwyBo4NaA6u29qwnOGGdFjb4Aw 6ifREqBdkEaYq5XSD1L1JdqfWgu+DC9OxaquZQvl/EJZX+Szn7josgahFK9dgof2ln uiLMv91DE4LAQ== From: "Harry Yoo (Oracle)" To: Andrew Morton , Vlastimil Babka , Alexei Starovoitov , Shakeel Butt , Harry Yoo Cc: Harry Yoo , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH mm-hotfixes 1/2] mm/page_alloc: return NULL early from alloc_frozen_pages_nolock() in NMI on UP Date: Mon, 27 Apr 2026 14:47:34 +0900 Message-ID: <20260427054736.566559-2-harry@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260427054736.566559-1-harry@kernel.org> References: <20260427054736.566559-1-harry@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: A3C82C0008 X-Stat-Signature: ugujxte7z61j6k63ho8enpfiu4eam1nj X-HE-Tag: 1777268863-463018 X-HE-Meta: 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 R+mSZHRc df9LRGdLqL1njfgqiPzrgFJ2wAddA7Y7cSgNnM6A7JFQBoX2evDGhDB2/+3t1xnJ9+6J9cvf8T8Tl24OsF5kF4X/IGvQG2VhS5bi+v369eD6Q9wQ6enK4Zc/yZUZ/zJpQ/wL842oobmcKs4/R0u/s8ZxnnU0390l99VG2akIopvzNri+HNrMCogO7Gd5s5jhgZrlZxwjoS3DV79BobMtn5k0/zpYnfycdvTGreyYX5CknmNcuBmxLTXHsP3kmsbO3Tzg8nDhlR6nAgY6JlGHvmb9TPnHNNOu05nYQ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On UP kernels (!CONFIG_SMP), spin_trylock() is a no-op that unconditionally succeeds even when the lock is already held. As a result, alloc_frozen_pages_nolock() called from NMI context can re-enter rmqueue() and acquire the zone lock that the interrupted context is already holding, corrupting the freelists. With CONFIG_DEBUG_SPINLOCK on UP, the following BUG is triggered with the slub_kunit test module: BUG: spinlock trylock failure on UP on CPU#0, kunit_try_catch/243 [...] Call Trace: dump_stack_lvl+0x3f/0x60 do_raw_spin_trylock+0x41/0x50 _raw_spin_trylock+0x24/0x50 rmqueue.isra.0+0x2a9/0xa70 get_page_from_freelist+0xeb/0x450 alloc_frozen_pages_nolock_noprof+0x111/0x1e0 allocate_slab+0x42a/0x500 ___slab_alloc+0xa7/0x4c0 kmalloc_nolock_noprof+0x164/0x310 [...] Fix this by returning NULL early when invoked from NMI on a UP kernel. Link: https://lore.kernel.org/linux-mm/ad_cqe51pvr1WaDg@hyeyoo Fixes: d7242af86434 ("mm: Introduce alloc_frozen_pages_nolock()") Signed-off-by: Harry Yoo (Oracle) --- mm/page_alloc.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 71859993dd54..23c7298d3be2 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7737,6 +7737,11 @@ struct page *alloc_frozen_pages_nolock_noprof(gfp_t gfp_flags, int nid, unsigned */ if (IS_ENABLED(CONFIG_PREEMPT_RT) && (in_nmi() || in_hardirq())) return NULL; + + /* On UP, spin_trylock() always succeeds even when it is locked */ + if (!IS_ENABLED(CONFIG_SMP) && in_nmi()) + return NULL; + if (!pcp_allowed_order(order)) return NULL; -- 2.43.0