Patch "vmalloc: fix __GFP_HIGHMEM usage for vmalloc_32 on 32b systems" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

vmalloc: fix __GFP_HIGHMEM usage for vmalloc_32 on 32b systems

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:

     vmalloc-fix-__gfp_highmem-usage-for-vmalloc_32-on-32b-systems.patch

and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Michal Hocko <[email protected]>
Date: Wed, 21 Feb 2018 14:46:01 -0800
Subject: vmalloc: fix __GFP_HIGHMEM usage for vmalloc_32 on 32b systems
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From: Michal Hocko <[email protected]>

commit 698d0831ba87b92ae10b15e8203cfd59f5a59a35 upstream.

Kai Heng Feng has noticed that BUG_ON(PageHighMem(pg)) triggers in drivers/media/common/saa7146/saa7146_core.c since 19809c2da28a ("mm,
vmalloc: use __GFP_HIGHMEM implicitly").

saa7146_vmalloc_build_pgtable uses vmalloc_32 and it is reasonable to expect that the resulting page is not in highmem. The above commit aimed to add __GFP_HIGHMEM only for those requests which do not specify any zone modifier gfp flag. vmalloc_32 relies on GFP_VMALLOC32 which should do the right thing. Except it has been missed that GFP_VMALLOC32 is an alias for GFP_KERNEL on 32b architectures. Thanks to Matthew to notice this.

Fix the problem by unconditionally setting GFP_DMA32 in GFP_VMALLOC32 for !64b arches (as a bailout). This should do the right thing and use ZONE_NORMAL which should be always below 4G on 32b systems.

Debugged by Matthew Wilcox.

---
 mm/vmalloc.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

@@ -1943,11 +1943,15 @@ void *vmalloc_exec(unsigned long size)
 }
 
 #if defined(CONFIG_64BIT) && defined(CONFIG_ZONE_DMA32)
-#define GFP_VMALLOC32 GFP_DMA32 | GFP_KERNEL
+#define GFP_VMALLOC32 (GFP_DMA32 | GFP_KERNEL)
 #elif defined(CONFIG_64BIT) && defined(CONFIG_ZONE_DMA)
-#define GFP_VMALLOC32 GFP_DMA | GFP_KERNEL
+#define GFP_VMALLOC32 (GFP_DMA | GFP_KERNEL)
 #else
-#define GFP_VMALLOC32 GFP_KERNEL
+/*
+ * 64b systems should always have either DMA or DMA32 zones. For others
+ * GFP_DMA32 should do the right thing and use the normal zone.
+ */
+#define GFP_VMALLOC32 GFP_DMA32 | GFP_KERNEL
 #endif
 
 /**

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/vmalloc-fix-__gfp_highmem-usage-for-vmalloc_32-on-32b-systems.patch