linux-kernel - [PATCH] memblocks: Move late alloc warning down to phys alloc

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Date: Fri, 14 Jun 2024 15:30:16 +0200
From: James Gowans <jgowans@...zon.com>
To: Mike Rapoport <rppt@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>
CC: James Gowans <jgowans@...zon.com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>, Alex Graf <graf@...zon.de>
Subject: [PATCH] memblocks: Move late alloc warning down to phys alloc

If a driver/subsystem tries to do an allocation after memblocks have
been freed and the memory handed to the buddy allocator, it will not
actually be legal to use that allocation - the buddy allocator owns the
memory. This is handled by the memblocks function which does allocations
and returns virtual addresses by printing a warning and doing a kmalloc
instead. However, the physical allocation function does not to do this
check - callers of the physical alloc function are unprotected against
mis-use.

Improve the error catching here by moving the check into the physical
allocation function which is used by the virtual addr allocation
function.

Signed-off-by: James Gowans <jgowans@...zon.com>
Cc: Mike Rapoport <rppt@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Alex Graf <graf@...zon.de>
---
 mm/memblock.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/mm/memblock.c b/mm/memblock.c
index d09136e040d3..dd4f237dc1fc 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1457,6 +1457,17 @@ phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size,
 		align = SMP_CACHE_BYTES;
 	}
 
+	/*
+	 * Detect any accidental use of these APIs after slab is ready, as at
+	 * this moment memblock may be deinitialized already and its
+	 * internal data may be destroyed (after execution of memblock_free_all)
+	 */
+	if (WARN_ON_ONCE(slab_is_available())) {
+		void *vaddr = kzalloc_node(size, GFP_NOWAIT, nid);
+
+		return vaddr ? virt_to_phys(vaddr) : 0;
+	}
+
 again:
 	found = memblock_find_in_range_node(size, align, start, end, nid,
 					    flags);
@@ -1576,13 +1587,6 @@ static void * __init memblock_alloc_internal(
 {
 	phys_addr_t alloc;
 
-	/*
-	 * Detect any accidental use of these APIs after slab is ready, as at
-	 * this moment memblock may be deinitialized already and its
-	 * internal data may be destroyed (after execution of memblock_free_all)
-	 */
-	if (WARN_ON_ONCE(slab_is_available()))
-		return kzalloc_node(size, GFP_NOWAIT, nid);
 
 	if (max_addr > memblock.current_limit)
 		max_addr = memblock.current_limit;
-- 
2.34.1