+ mm-vmalloc-bail-out-if-in-softirq-context.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/vmalloc: bail out if in softirq context
has been added to the -mm mm-unstable branch.  Its filename is
     mm-vmalloc-bail-out-if-in-softirq-context.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmalloc-bail-out-if-in-softirq-context.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Subject: mm/vmalloc: bail out if in softirq context
Date: Mon, 26 Oct 2026 11:25:03 +0100

vmalloc() is not allowed to be invoked from the NMI, hard-irq and softirq
contexts because doing so may deadlock on internal locks.

Commit 04aa71da5f35 ("mm/vmalloc: do not trigger BUG() on BH disabled
context") replaced the deprecated in_interrupt() macro with explicit
in_nmi() and in_hardirq() checks, but unintentionally dropped the softirq
context check.

Example:

<snip>
vzalloc() in a task
 spin_lock(&vn->busy.lock)
  <------ Hard irq
   irq_exit()
    process softirq on the same CPU
     vmalloc()
      spin_lock(&vn->busy.lock)
       spins forever
<snip>

Restore the check by checking the caller's context with the
in_serving_softirq() helper.  Note that, it is still allowed to invoke
vmalloc() with disabled bottom halves.

Replace BUG_ON() with WARN_ON_ONCE() for in_nmi() and
in_hardirq() case.

Link: https://lore.kernel.org/20261026102503.30860-1-urezki@gmail.com
Fixes: 04aa71da5f35 ("mm/vmalloc: do not trigger BUG() on BH disabled context")
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: <stable@vger.kernel.org>
---

 mm/vmalloc.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/mm/vmalloc.c~mm-vmalloc-bail-out-if-in-softirq-context
+++ a/mm/vmalloc.c
@@ -3271,7 +3271,13 @@ struct vm_struct *__get_vm_area_node(uns
 	struct vm_struct *area;
 	unsigned long requested_size = size;
 
-	BUG_ON(in_nmi() || in_hardirq());
+	/* IRQ re-entrancy -> irq_exit() -> process softirq. */
+	if (in_serving_softirq())
+		return NULL;
+
+	if (WARN_ON_ONCE(in_nmi() || in_hardirq()))
+		return NULL;
+
 	size = ALIGN(size, 1ul << shift);
 	if (unlikely(!size))
 		return NULL;
_

Patches currently in -mm which might be from urezki@gmail.com are

mm-vmalloc-use-dedicated-unbound-workqueues-for-vmap-drain.patch
mm-vmalloc-bail-out-if-in-softirq-context.patch