[SRU] [Artful] [PATCH 1/1] vmalloc: fix __GFP_HIGHMEM usage for vmalloc_32 on 32b systems

[Kai-Heng Feng]

From: Michal Hocko <mhocko at suse.com>

BugLink: https://bugs.launchpad.net/bugs/1742316

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.

[akpm at linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20180212095019.GX21609@dhcp22.suse.cz
Fixes: 19809c2da28a ("mm, vmalloc: use __GFP_HIGHMEM implicitly”)
Signed-off-by: Michal Hocko <mhocko at suse.com>
Reported-by: Kai Heng Feng <kai.heng.feng at canonical.com>
Cc: Matthew Wilcox <willy at infradead.org>
Cc: Laura Abbott <labbott at redhat.com>
Cc: <stable at vger.kernel.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
(cherry picked from commit 698d0831ba87b92ae10b15e8203cfd59f5a59a35)
Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
---
 mm/vmalloc.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index ceacc6e01904..07b4deef6faa 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1945,11 +1945,15 @@ 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
 
 /**
-- 
2.15.1