+ kexec-fix-a-memory-leak-in-crash_shrink_memory.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: kexec: fix a memory leak in crash_shrink_memory()
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     kexec-fix-a-memory-leak-in-crash_shrink_memory.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kexec-fix-a-memory-leak-in-crash_shrink_memory.patch

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

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------------------------------------------------------
From: Zhen Lei <thunder.leizhen@huawei.com>
Subject: kexec: fix a memory leak in crash_shrink_memory()
Date: Sat, 27 May 2023 20:34:34 +0800

Patch series "kexec: enable kexec_crash_size to support two crash kernel
regions".

When crashkernel=X fails to reserve region under 4G, it will fall back to
reserve region above 4G and a region of the default size will also be
reserved under 4G.  Unfortunately, /sys/kernel/kexec_crash_size only
supports one crash kernel region now, the user cannot sense the low memory
reserved by reading /sys/kernel/kexec_crash_size.  Also, low memory cannot
be freed by writing this file.

For example:
resource_size(crashk_res) = 512M
resource_size(crashk_low_res) = 256M

The result of 'cat /sys/kernel/kexec_crash_size' is 512M, but it should be
768M.  When we execute 'echo 0 > /sys/kernel/kexec_crash_size', the size
of crashk_res becomes 0 and resource_size(crashk_low_res) is still 256 MB,
which is incorrect.

Since crashk_res manages the memory with high address and crashk_low_res
manages the memory with low address, crashk_low_res is shrunken only when
all crashk_res is shrunken.  And because when there is only one crash
kernel region, crashk_res is always used.  Therefore, if all crashk_res is
shrunken and crashk_low_res still exists, swap them.


This patch (of 6):

If the value of parameter 'new_size' is in the semi-open and semi-closed
interval (crashk_res.end - KEXEC_CRASH_MEM_ALIGN + 1, crashk_res.end], the
calculation result of ram_res is:

	ram_res->start = crashk_res.end + 1
	ram_res->end   = crashk_res.end

The operation of insert_resource() fails, and ram_res is not added to
iomem_resource.  As a result, the memory of the control block ram_res is
leaked.

In fact, on all architectures, the start address and size of crashk_res
are already aligned by KEXEC_CRASH_MEM_ALIGN.  Therefore, we do not need
to round up crashk_res.start again.  Instead, we should round up
'new_size' in advance.

Link: https://lkml.kernel.org/r/20230527123439.772-1-thunder.leizhen@huawei.com
Link: https://lkml.kernel.org/r/20230527123439.772-2-thunder.leizhen@huawei.com
Fixes: 6480e5a09237 ("kdump: add missing RAM resource in crash_shrink_memory()")
Fixes: 06a7f711246b ("kexec: premit reduction of the reserved memory size")
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Cong Wang <amwang@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/kexec_core.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/kernel/kexec_core.c~kexec-fix-a-memory-leak-in-crash_shrink_memory
+++ a/kernel/kexec_core.c
@@ -1122,6 +1122,7 @@ int crash_shrink_memory(unsigned long ne
 	start = crashk_res.start;
 	end = crashk_res.end;
 	old_size = (end == 0) ? 0 : end - start + 1;
+	new_size = roundup(new_size, KEXEC_CRASH_MEM_ALIGN);
 	if (new_size >= old_size) {
 		ret = (new_size == old_size) ? 0 : -EINVAL;
 		goto unlock;
@@ -1133,9 +1134,7 @@ int crash_shrink_memory(unsigned long ne
 		goto unlock;
 	}
 
-	start = roundup(start, KEXEC_CRASH_MEM_ALIGN);
-	end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN);
-
+	end = start + new_size;
 	crash_free_reserved_phys_range(end, crashk_res.end);
 
 	if ((start == end) && (crashk_res.parent != NULL))
_

Patches currently in -mm which might be from thunder.leizhen@huawei.com are

kexec-fix-a-memory-leak-in-crash_shrink_memory.patch
kexec-delete-a-useless-check-in-crash_shrink_memory.patch
kexec-clear-crashk_res-if-all-its-memory-has-been-released.patch
kexec-improve-the-readability-of-crash_shrink_memory.patch
kexec-add-helper-__crash_shrink_memory.patch
kexec-enable-kexec_crash_size-to-support-two-crash-kernel-regions.patch