[PATCH 6.9 084/143] s390/mm: Add NULL pointer check to crst_table_free() base_crst_free()

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6.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Heiko Carstens <hca@xxxxxxxxxxxxx>

commit b5efb63acf7bddaf20eacfcac654c25c446eabe8 upstream.

crst_table_free() used to work with NULL pointers before the conversion
to ptdescs.  Since crst_table_free() can be called with a NULL pointer
(error handling in crst_table_upgrade() add an explicit check.

Also add the same check to base_crst_free() for consistency reasons.

In real life this should not happen, since order two GFP_KERNEL
allocations will not fail, unless FAIL_PAGE_ALLOC is enabled and used.

Reported-by: Yunseong Kim <yskelg@xxxxxxxxx>
Fixes: 6326c26c1514 ("s390: convert various pgalloc functions to use ptdescs")
Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
Acked-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxx
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/s390/mm/pgalloc.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/arch/s390/mm/pgalloc.c
+++ b/arch/s390/mm/pgalloc.c
@@ -55,6 +55,8 @@ unsigned long *crst_table_alloc(struct m
 
 void crst_table_free(struct mm_struct *mm, unsigned long *table)
 {
+	if (!table)
+		return;
 	pagetable_free(virt_to_ptdesc(table));
 }
 
@@ -262,6 +264,8 @@ static unsigned long *base_crst_alloc(un
 
 static void base_crst_free(unsigned long *table)
 {
+	if (!table)
+		return;
 	pagetable_free(virt_to_ptdesc(table));
 }
 






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