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mm/page_alloc: return NULL early from alloc_frozen_pages_nolock() in NMI on UP

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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:
   <NMI>
   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
   [...]
   </NMI>

Fix this by returning NULL early when invoked from NMI on a UP kernel.

Link: https://lore.kernel.org/linux-mm/ad_cqe51pvr1WaDg@hyeyoo
Cc: stable@vger.kernel.org
Fixes: d7242af864 ("mm: Introduce alloc_frozen_pages_nolock()")
Signed-off-by: Harry Yoo (Oracle) <harry@kernel.org>
Link: https://patch.msgid.link/20260427-nolock-api-fix-v2-1-a6b83a92d9a4@kernel.org
Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
This commit is contained in:
Harry Yoo (Oracle)
2026-04-27 16:09:52 +09:00
committed by Vlastimil Babka (SUSE)
parent 082a6d03a2
commit 620b46ed6a
1 changed files with 5 additions and 0 deletions
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5
mm/page_alloc.c
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@@ -7775,6 +7775,11 @@ 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;