Re: [PATCH] mm/sparse: Fix kernel crash with pfn_section_valid check
From: Aneesh Kumar K.V <hidden>
Date: 2020-03-25 08:12:54
Also in:
linux-mm, lkml
On 3/25/20 1:07 PM, Baoquan He wrote:
quoted hunk ↗ jump to hunk
On 03/25/20 at 03:06pm, Baoquan He wrote:quoted
On 03/25/20 at 08:49am, Aneesh Kumar K.V wrote:quoted
quoted
mm/sparse.c | 2 ++ 1 file changed, 2 insertions(+)diff --git a/mm/sparse.c b/mm/sparse.c index aadb7298dcef..3012d1f3771a 100644 --- a/mm/sparse.c +++ b/mm/sparse.c@@ -781,6 +781,8 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages, ms->usage = NULL; } memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr); + /* Mark the section invalid */ + ms->section_mem_map &= ~SECTION_HAS_MEM_MAP;Not sure if we should add checking in valid_section() or pfn_valid(), e.g check ms->usage validation too. Otherwise, this fix looks good to me.With SPASEMEM_VMEMAP enabled, we should do validation check on ms->usage before checking any subsection is valid. Since now we do have case in which ms->usage is released, people still try to check it.diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index f0a2c184eb9a..d79bd938852e 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h@@ -1306,6 +1306,8 @@ static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn) { int idx = subsection_map_index(pfn); + if (!ms->usage) + return 0; return test_bit(idx, ms->usage->subsection_map); } #else
We always check for section valid, before we check if pfn_section_valid(). static inline int pfn_valid(unsigned long pfn) struct mem_section *ms; if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS) return 0; ms = __nr_to_section(pfn_to_section_nr(pfn)); if (!valid_section(ms)) return 0; /* * Traditionally early sections always returned pfn_valid() for * the entire section-sized span. */ return early_section(ms) || pfn_section_valid(ms, pfn); } IMHO adding that if (!ms->usage) is redundant. -aneesh