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b=EknsdmMD/enifxH8VPV8H+qG6cwpocmLVCoiW7B+3U7CZljO4P8/YYBWxa1/ROzU8 5ciro/zNJL6+1Ekw1qf5xfG3uc+nh7aJzzgL/TZKhuVnl5kks9BGc5lwmNq5ViRa/w Bf/uZ/gLam1vEH2k5RbicgvTK8CYkGZbyM7chBtwS0Qllmx/Q8HRc3P2RLDvo1t+zH 7Bn6D1RYgkGkRiD6Cvf8RBbVr8vT32IWvqi/NN/jFvut9fFUm+lBC67M2oAFHZNkmh 8LO/IZzH/MFsYY1f/VGTRljSoMJ7Qs5tz5eRiHKLMDLhjE/Nj7H1rIobveui/U+LyO 5elLbmHn4l2gw== From: "Harry Yoo (Oracle)" To: Andrew Morton , Vlastimil Babka , Shakeel Butt , Alexei Starovoitov , 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 14:42:03 +0900 Message-ID: <20260427054205.560734-2-harry@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260427054205.560734-1-harry@kernel.org> References: <20260427054205.560734-1-harry@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: D59ACC0002 X-Stat-Signature: ugujxte7z61j6k63ho8enpfiu4eam1nj X-HE-Tag: 1777268532-388145 X-HE-Meta: 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 a7+r62CJ nVKhohCW3UEJK9Gt00xiPwu8OwTF5NIr/3aLK+uKPpSgaAnLYJvKsZF5xwsNrsv3W6obK4lwfhLWfugxn4RCqdZ65oKcAn+QtzFtVKrznbbhCly3v3MY03wmiID5iziMfcMCgQqqZoiw8I3DGVjXxzpYiNITq7gTN/4cH8QpHUA72ZsA9c1qsyGppeGI4i4TVYPYBt7fmeBF1LuD5sGdLaqUwEwtome4b+vT1ZGu7DihoPir0tM3clZTVTgsNpV4hn8UlIV71+ArSzqr7Fhw+svxJwR40E4ccEN90 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