[tip:x86/urgent] x86/dma-mapping: Fix arch_dma_alloc_attrs() oops with NULL dev

From: tip-bot for Ville SyrjÃlÃ
Date: Mon Oct 26 2015 - 02:04:01 EST

Commit-ID: 298a96c12b2d8fd845ae0c2c21c0a1c0b470f99e
Gitweb: http://git.kernel.org/tip/298a96c12b2d8fd845ae0c2c21c0a1c0b470f99e
Author: Ville SyrjÃlà <ville.syrjala@xxxxxxxxxxxxxxx>
AuthorDate: Sun, 25 Oct 2015 23:11:43 +0200
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Mon, 26 Oct 2015 14:59:36 +0900

x86/dma-mapping: Fix arch_dma_alloc_attrs() oops with NULL dev

Commit 6894258eda2f broke drivers that pass NULL as the device pointer
to dma_alloc. The reason is that arch_dma_alloc_attrs() now calls
dma_alloc_coherent_gfp_flags() which in turn calls
dma_alloc_coherent_mask(), where the device pointer is dereferenced

Fix things by moving the ISA DMA fallback device assignment before the
call to dma_alloc_coherent_gfp_flags().

Fixes: 6894258eda2f ("dma-mapping: consolidate dma_{alloc,free}_{attrs,coherent}")
Reported-and-tested-by: Meelis Roos <mroos@xxxxxxxx>
Signed-off-by: Ville SyrjÃlà <ville.syrjala@xxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Link: http://lkml.kernel.org/r/1445807503-8920-1-git-send-email-ville.syrjala@xxxxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
arch/x86/kernel/pci-dma.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 1b55de1..cd99433 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -131,11 +131,12 @@ void dma_generic_free_coherent(struct device *dev, size_t size, void *vaddr,

bool arch_dma_alloc_attrs(struct device **dev, gfp_t *gfp)
+ if (!*dev)
+ *dev = &x86_dma_fallback_dev;
*gfp &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
*gfp = dma_alloc_coherent_gfp_flags(*dev, *gfp);

- if (!*dev)
- *dev = &x86_dma_fallback_dev;
if (!is_device_dma_capable(*dev))
return false;
return true;
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