Messages in this thread | | | Subject | Re: [PATCH] mm/sparse: Fix kernel crash with pfn_section_valid check | From | "Aneesh Kumar K.V" <> | Date | Wed, 25 Mar 2020 13:42:25 +0530 |
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On 3/25/20 1:07 PM, Baoquan He wrote: > On 03/25/20 at 03:06pm, Baoquan He wrote: >> On 03/25/20 at 08:49am, Aneesh Kumar K.V wrote: > >>> 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
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