[merged mm-stable] mm-page_alloc-dont-spin_trylock-in-nmi-on-up.patch removed from -mm tree

The quilt patch titled
     Subject: mm/page_alloc: don't spin_trylock() in NMI on UP
has been removed from the -mm tree.  Its filename was
     mm-page_alloc-dont-spin_trylock-in-nmi-on-up.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Brendan Jackman <[email protected]>
Subject: mm/page_alloc: don't spin_trylock() in NMI on UP
Date: Wed, 15 Jul 2026 09:03:58 +0000

Patch series "mm/page_alloc: fixes for free_pages_nolock() on RT/UP".

Pre-existing bugs found by Sashiko during review of this other series:
https://lore.kernel.org/all/[email protected]/

I have not reproduced these bugs, and I suspect there is no real-world
user that is affected by them.


This patch (of 2):

As noted in can_spin_trylock(), using this is unsafe in this context. 
commit 620b46ed6ae17 ("mm/page_alloc: return NULL early from
alloc_frozen_pages_nolock() in NMI on UP") fixed this on the alloc side
but missed the free side.

Impact: If BPF programs using these features in NMI (probably tracing) are
present on non-SMP builds this might crash the kernel and is probably
exploitable by local attackers for privilege escalation.

Link: https://lore.kernel.org/[email protected]
Link: https://lore.kernel.org/[email protected]
Fixes: 8c57b687e833 ("mm, bpf: Introduce free_pages_nolock()")
Signed-off-by: Brendan Jackman <[email protected]>
Reported-by: [email protected]
Closes: https://sashiko.dev/#/patchset/20260703-alloc-trylock-v5-0-c87b714e19d3%40google.com?part=18
Reviewed-by: Vlastimil Babka (SUSE) <[email protected]>
Reviewed-by: Harry Yoo (Oracle) <[email protected]>
Cc: Brendan Jackman <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Sebastian Andrzej Siewior <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Zi Yan <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---

 mm/page_alloc.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/mm/page_alloc.c~mm-page_alloc-dont-spin_trylock-in-nmi-on-up
+++ a/mm/page_alloc.c
@@ -2979,8 +2979,7 @@ static void __free_frozen_pages(struct p
 		migratetype = MIGRATE_MOVABLE;
 	}
 
-	if (unlikely((fpi_flags & FPI_TRYLOCK) && IS_ENABLED(CONFIG_PREEMPT_RT)
-		     && (in_nmi() || in_hardirq()))) {
+	if (unlikely((fpi_flags & FPI_TRYLOCK) && !can_spin_trylock())) {
 		add_page_to_zone_llist(zone, page, order);
 		return;
 	}
_

Patches currently in -mm which might be from [email protected] are