The patch titled
Subject: mm/sparsemem: fix race in accessing memory_section->usage
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-sparsemem-fix-race-in-accessing-memory_section-usage-v2.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-sparsemem-fix-race-in-accessing-memory_section-usage-v2.patch
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: Charan Teja Kalla <quic_charante@xxxxxxxxxxx>
Subject: mm/sparsemem: fix race in accessing memory_section->usage
Date: Fri, 27 Oct 2023 16:19:38 +0530
use kfree_rcu() in place of synchronize_rcu(), per David
Link: https://lkml.kernel.org/r/1698403778-20938-1-git-send-email-quic_charante@xxxxxxxxxxx
Fixes: f46edbd1b151 ("mm/sparsemem: add helpers track active portions of a section at boot")
Signed-off-by: Charan Teja Kalla <quic_charante@xxxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mmzone.h | 3 ++-
mm/sparse.c | 5 ++---
2 files changed, 4 insertions(+), 4 deletions(-)
--- a/include/linux/mmzone.h~mm-sparsemem-fix-race-in-accessing-memory_section-usage-v2
+++ a/include/linux/mmzone.h
@@ -1770,6 +1770,7 @@ static inline unsigned long section_nr_t
#define SUBSECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SUBSECTION_MASK)
struct mem_section_usage {
+ struct rcu_head rcu;
#ifdef CONFIG_SPARSEMEM_VMEMMAP
DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION);
#endif
@@ -1963,7 +1964,7 @@ static inline int pfn_section_valid(stru
{
int idx = subsection_map_index(pfn);
- return test_bit(idx, ms->usage->subsection_map);
+ return test_bit(idx, READ_ONCE(ms->usage)->subsection_map);
}
#else
static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn)
--- a/mm/sparse.c~mm-sparsemem-fix-race-in-accessing-memory_section-usage-v2
+++ a/mm/sparse.c
@@ -806,9 +806,8 @@ static void section_deactivate(unsigned
* was allocated during boot.
*/
if (!PageReserved(virt_to_page(ms->usage))) {
- synchronize_rcu();
- kfree(ms->usage);
- ms->usage = NULL;
+ kfree_rcu(ms->usage, rcu);
+ WRITE_ONCE(ms->usage, NULL);
}
memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
}
_
Patches currently in -mm which might be from quic_charante@xxxxxxxxxxx are
mm-sparsemem-fix-race-in-accessing-memory_section-usage.patch
mm-sparsemem-fix-race-in-accessing-memory_section-usage-v2.patch
