linux-kernel - Re: [PATCH v2] memblock: Move late alloc warning down to phys alloc

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Message-ID: <20240621011511.cveqjhnpauhze4jl@master>
Date: Fri, 21 Jun 2024 01:15:11 +0000
From: Wei Yang <richard.weiyang@...il.com>
To: James Gowans <jgowans@...zon.com>
Cc: Mike Rapoport <rppt@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Alex Graf <graf@...zon.de>
Subject: Re: [PATCH v2] memblock: Move late alloc warning down to phys alloc

On Wed, Jun 19, 2024 at 11:55:55AM +0200, James Gowans wrote:
>If a driver/subsystem tries to do an allocation after the memblock
>allocations 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. Currently this mis-use is handled by
>the memblock 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>

Reviewed-by: Wei Yang <richard.weiyang@...il.com>

>---
>
>Notes:
>    Changes since v1: https://lore.kernel.org/all/20240614133016.134150-1-jgowans@amazon.com/
>    - Move this late usage check before alignment check
>    - Replace memblocks with memblock
>
> mm/memblock.c | 18 +++++++++++-------
> 1 file changed, 11 insertions(+), 7 deletions(-)
>
>diff --git a/mm/memblock.c b/mm/memblock.c
>index d09136e040d3..dbb3d700247e 100644
>--- a/mm/memblock.c
>+++ b/mm/memblock.c
>@@ -1451,6 +1451,17 @@ phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size,
> 	if (WARN_ONCE(nid == MAX_NUMNODES, "Usage of MAX_NUMNODES is deprecated. Use NUMA_NO_NODE instead\n"))
> 		nid = NUMA_NO_NODE;
> 
>+	/*
>+	 * 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;
>+	}
>+
> 	if (!align) {
> 		/* Can't use WARNs this early in boot on powerpc */
> 		dump_stack();
>@@ -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
>

-- 
Wei Yang
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