mm: kmemleak: fix upper boundary check for physical address objects

commit 488b5b9
Author: Catalin Marinas <[email protected]>
Date:   Mon Jan 27 18:42:33 2025 +0000

    mm: kmemleak: fix upper boundary check for physical address objects

    Memblock allocations are registered by kmemleak separately, based on their
    physical address.  During the scanning stage, it checks whether an object
    is within the min_low_pfn and max_low_pfn boundaries and ignores it
    otherwise.

    With the recent addition of __percpu pointer leak detection (commit
    6c99d4e ("kmemleak: enable tracking for percpu pointers")), kmemleak
    started reporting leaks in setup_zone_pageset() and
    setup_per_cpu_pageset().  These were caused by the node_data[0] object
    (initialised in alloc_node_data()) ending on the PFN_PHYS(max_low_pfn)
    boundary.  The non-strict upper boundary check introduced by commit
    84c3262 ("mm: kmemleak: check physical address when scan") causes the
    pg_data_t object to be ignored (not scanned) and the __percpu pointers it
    contains to be reported as leaks.

    Make the max_low_pfn upper boundary check strict when deciding whether to
    ignore a physical address object and not scan it.

    Link: https://lkml.kernel.org/r/[email protected]
    Fixes: 84c3262 ("mm: kmemleak: check physical address when scan")
    Signed-off-by: Catalin Marinas <[email protected]>
    Reported-by: Jakub Kicinski <[email protected]>
    Tested-by: Matthieu Baerts (NGI0) <[email protected]>
    Cc: Patrick Wang <[email protected]>
    Cc: <[email protected]>    [6.0.x]
    Signed-off-by: Andrew Morton <[email protected]>

JIRA: https://issues.redhat.com/browse/RHEL-77742
Signed-off-by: Nico Pache <[email protected]>

Author: PacheNico

mm/kmemleak.c

@@ -1689,7 +1689,7 @@ static void kmemleak_scan(void)
 			unsigned long phys = object->pointer;
 
 			if (PHYS_PFN(phys) < min_low_pfn ||
-			    PHYS_PFN(phys + object->size) >= max_low_pfn)
+			    PHYS_PFN(phys + object->size) > max_low_pfn)
 				__paint_it(object, KMEMLEAK_BLACK);
 		}