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b=cUBNH1Da8+rgcNrWLu/NS8WKGa50Nfcmuq/qgpI0tS114WnTsOpODhMiCubEqJOv+ DY8eK0USdbnNsPHRoAsbxIrek+eLAti5oijZpfZDu3HTbgw03OyaM7F5iMfuEU/1I1 yw1vXE0rW/iLqTA1GWfmoV9RewEExjj2BxJvth/uH/4xpVrajB9GWgseBX1QFNLLNy 3m6ZadlQB1q9Ziuounl2qn2BF1fO0NbMl1EqEtXUnYz8/hxsg55Pc0MQ28cn4QNtdD h5NdPjidWU+BuPTD5Bnh9dLYOKmF1clsELiKndcnp8pcJ5PVmLag3BtOFA8hYJK6xI GLtMDrattAWsA== From: "Harry Yoo (Oracle)" To: Vlastimil Babka , Harry Yoo , Andrew Morton , Alexei Starovoitov Cc: Harry Yoo , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH mm-hotfixes 2/2] mm/slub: return NULL early from kmalloc_nolock() in NMI on UP Date: Mon, 27 Apr 2026 14:47:35 +0900 Message-ID: <20260427054736.566559-3-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-Queue-Id: 51A33A0003 X-Rspamd-Server: rspam04 X-Stat-Signature: ggz1jxcd3fw847k1jneemrxzizocqqx7 X-HE-Tag: 1777268866-312276 X-HE-Meta: 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 B+uDFTNk PM0rvhdBaUPto51NXSWUo6RPMKl/2sjrAeUPNOdWuIkn3XjBwXHk4BMt/+dyaaqV1z6yfqM1/AiyZ35GR58WDfeYzFORymnHRLnkKCVDeRK760T72fJLP+jf35ALjq56fMrNAf5nZ+azHl7Dv8UZzfF7UXuK8vCpSrgGLS11nmfCTPYY1qoE6+Di2NGJH9iYaP0X8YFZ/W6A5tI2KokpRkBwFnaI4aEGQ4pUepx3yPj4aVGj8mfb/huGJnvQ0tWdu2Y/dodyZZUM/8sZC4dAXPKFsow== 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, kmalloc_nolock() called from NMI context can re-enter the slab allocator and acquire a lock that the interrupted context is already holding, corrupting slab state. 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 get_from_partial_node+0x120/0x4d0 ___slab_alloc+0x8a/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: af92793e52c3 ("slab: Introduce kmalloc_nolock() and kfree_nolock().") Signed-off-by: Harry Yoo (Oracle) --- mm/slub.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/slub.c b/mm/slub.c index 92362eeb13e5..b4ec15df92f6 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -5339,6 +5339,10 @@ void *kmalloc_nolock_noprof(size_t size, gfp_t gfp_flags, int node) 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; + retry: if (unlikely(size > KMALLOC_MAX_CACHE_SIZE)) return NULL; -- 2.43.0