[PATCH v1 0/2] Fixes for kmemleak tracking with CMA regions

Isaac J. Manjarres
2023-01-09T22:16:34Z

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 page-fault 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 created at specific memory addresses or
dynamically allocated within a range of addresses. However, if the
CMA region is constrained to a certain range of addresses through the
command line, the region is reserved through the memblock_reserve()
function, but kmemleak_alloc_phys() is not invoked. Furthermore,
kmemleak is never informed about CMA regions being freed to buddy at
boot, which is problematic when CONFIG_DEBUG_PAGEALLOC is enabled, as
all CMA regions are unmapped from the kernel's address space, and
subsequently causes a page-fault when kmemleak attempts to scan any
of them.

This series makes it so that kmemleak is aware of every CMA region before
they are freed to the buddy allocator, so that at that time, kmemleak
can be informed that each region is about to be freed, and thus it
should not attempt to scan those regions.

Isaac J. Manjarres (2):
mm/cma.c: Make kmemleak aware of all CMA regions
mm/cma.c: Delete kmemleak objects when freeing CMA areas to buddy at
boot

mm/cma.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)

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2.39.0.314.g84b9a713c41-goog