| Message ID | 20250401202354.103501-2-sweettea-kernel@dorminy.me (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/khugepaged: fix a tracepoint for error cases | expand |
On Tue, 1 Apr 2025 16:23:53 -0400 Sweet Tea Dorminy <sweettea-kernel@dorminy.me> wrote: > Fix a potential NULL pointer dereference in trace_mm_khugepaged_scan_pmd() > when folio is NULL. This is possible if vm_normal_page() returned a NULL > page -- which is unlikely, but was hit in testing. > > (The tracepoint in include/trace/events/huge_memory.h can already deal > with a NULL page.) > > ... > > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1435,8 +1435,9 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm, > *mmap_locked = false; > } > out: > - trace_mm_khugepaged_scan_pmd(mm, &folio->page, writable, referenced, > - none_or_zero, result, unmapped); > + trace_mm_khugepaged_scan_pmd(mm, folio ? &folio->page : NULL, > + writable, referenced, none_or_zero, > + result, unmapped); > return result; Confused. If folio==NULL then &folio->page==NULL also. The patch appears to be a no-op? Do you have the messages from that oops?
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index cc945c6ab3bd..eb7b019159d4 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1435,8 +1435,9 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm, *mmap_locked = false; } out: - trace_mm_khugepaged_scan_pmd(mm, &folio->page, writable, referenced, - none_or_zero, result, unmapped); + trace_mm_khugepaged_scan_pmd(mm, folio ? &folio->page : NULL, + writable, referenced, none_or_zero, + result, unmapped); return result; }
Fix a potential NULL pointer dereference in trace_mm_khugepaged_scan_pmd() when folio is NULL. This is possible if vm_normal_page() returned a NULL page -- which is unlikely, but was hit in testing. (The tracepoint in include/trace/events/huge_memory.h can already deal with a NULL page.) Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me> --- Based on akpm/mm-unstable. mm/khugepaged.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) base-commit: e026356e4192ff5a52c1d535e6b9e3fa50def2c4