The patch titled Subject: of: reserved_mem: Have kmemleak ignore dynamically allocated reserved mem has been added to the -mm mm-hotfixes-unstable branch. Its filename is of-reserved_mem-have-kmemleak-ignore-dynamically-allocated-reserved-mem.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

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

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------------------------------------------------------ From: "Isaac J. Manjarres" isaacmanjarres@google.com Subject: of: reserved_mem: Have kmemleak ignore dynamically allocated reserved mem Date: Wed, 8 Feb 2023 15:20:00 -0800

Patch series "Fix kmemleak crashes when scanning CMA regions", v2.

When trying to boot a device with an ARM64 kernel with the following config options enabled:

CONFIG_DEBUG_PAGEALLOC=y CONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT=y CONFIG_DEBUG_KMEMLEAK=y

a crash is encountered when kmemleak starts to scan the list of gray or allocated objects that it maintains. Upon closer inspection, it was observed that these page-faults always occurred when kmemleak attempted to scan a CMA region.

At the moment, kmemleak is made aware of CMA regions that are specified through the devicetree to be dynamically allocated within a range of addresses. However, kmemleak should not need to scan CMA regions or any reserved memory region, as those regions can be used for DMA transfers between drivers and peripherals, and thus wouldn't contain anything useful for kmemleak.

Additionally, since CMA regions are unmapped from the kernel's address space when they are freed to the buddy allocator at boot when CONFIG_DEBUG_PAGEALLOC is enabled, kmemleak shouldn't attempt to access those memory regions, as that will trigger a crash. Thus, kmemleak should ignore all dynamically allocated reserved memory regions.

This patch (of 1):

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.

Link: https://lkml.kernel.org/r/20230208232001.2052777-1-isaacmanjarres@google.com Link: https://lkml.kernel.org/r/20230208232001.2052777-2-isaacmanjarres@google.com Fixes: a7259df76702 ("memblock: make memblock_find_in_range method private") Signed-off-by: Isaac J. Manjarres isaacmanjarres@google.com Cc: stable@vger.kernel.org [5.15+] Cc: Catalin Marinas catalin.marinas@arm.com Cc: Frank Rowand frowand.list@gmail.com Cc: Kirill A. Shutemov kirill.shtuemov@linux.intel.com Cc: Mike Rapoport (IBM) rppt@kernel.org Cc: Nick Kossifidis mick@ics.forth.gr Cc: Rafael J. Wysocki rafael.j.wysocki@intel.com Cc: Rob Herring robh@kernel.org Cc: Russell King (Oracle) rmk+kernel@armlinux.org.uk Cc: Saravana Kannan saravanak@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

--- a/drivers/of/of_reserved_mem.c~of-reserved_mem-have-kmemleak-ignore-dynamically-allocated-reserved-mem +++ a/drivers/of/of_reserved_mem.c @@ -48,9 +48,10 @@ static int __init early_init_dt_alloc_re err = memblock_mark_nomap(base, size); if (err) memblock_phys_free(base, size); - kmemleak_ignore_phys(base); }

+ kmemleak_ignore_phys(base); + return err; }

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Patches currently in -mm which might be from isaacmanjarres@google.com are

of-reserved_mem-have-kmemleak-ignore-dynamically-allocated-reserved-mem.patch