linux-kernel - [PATCH v2 1/1] of: reserved_mem: Have kmemleak ignore dynamically allocated reserved mem

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Message-ID: <20230208232001.2052777-2-isaacmanjarres@google.com>
Date:   Wed,  8 Feb 2023 15:20:00 -0800
From:   "Isaac J. Manjarres" <isaacmanjarres@...gle.com>
To:     Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Mike Rapoport <rppt@...nel.org>,
        "Kirill A. Shutemov" <kirill.shtuemov@...ux.intel.com>,
        Nick Kossifidis <mick@....forth.gr>,
        Catalin Marinas <catalin.marinas@....com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Saravana Kannan <saravanak@...gle.com>, linux-mm@...ck.org,
        "Isaac J. Manjarres" <isaacmanjarres@...gle.com>,
        kernel-team@...roid.com,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Rob Herring <robh@...nel.org>
Subject: [PATCH v2 1/1] of: reserved_mem: Have kmemleak ignore dynamically
 allocated reserved mem

Currently, kmemleak ignores dynamically allocated reserved memory
regions that don't have a kernel mapping. However, regions that do
retain a kernel mapping (e.g. CMA regions) do get scanned by kmemleak.

This is not ideal for two reasons:

1. kmemleak works by scanning memory regions for pointers to
allocated objects to determine if those objects have been leaked
or not. However, reserved memory regions can be used between drivers
and peripherals for DMA transfers, and thus, would not contain pointers
to allocated objects, making it unnecessary for kmemleak to scan
these reserved memory regions.

2. When CONFIG_DEBUG_PAGEALLOC is enabled, along with kmemleak, the
CMA reserved memory regions are unmapped from the kernel's address
space when they are freed to buddy at boot. These CMA reserved regions
are still tracked by kmemleak, however, and when kmemleak attempts to
scan them, a crash will happen, as accessing the CMA region will result
in a page-fault, since the regions are unmapped.

Thus, use kmemleak_ignore_phys() for all dynamically allocated reserved
memory regions, instead of those that do not have a kernel mapping
associated with them.

Cc: <stable@...r.kernel.org>    # 5.15+
Fixes: a7259df76702 ("memblock: make memblock_find_in_range method private")
Signed-off-by: Isaac J. Manjarres <isaacmanjarres@...gle.com>
---
 drivers/of/of_reserved_mem.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index 65f3b02a0e4e..f90975e00446 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -48,9 +48,10 @@ static int __init early_init_dt_alloc_reserved_memory_arch(phys_addr_t size,
 		err = memblock_mark_nomap(base, size);
 		if (err)
 			memblock_phys_free(base, size);
-		kmemleak_ignore_phys(base);
 	}

+	kmemleak_ignore_phys(base);
+
 	return err;
 }

-- 
2.39.1.581.gbfd45094c4-goog