[08/12] dax: Fix bogus fault return value on cow faults
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Message ID 1457637535-21633-9-git-send-email-jack@suse.cz
State New
Headers show

Commit Message

Jan Kara March 10, 2016, 7:18 p.m. UTC
In case of cow fault when there is no page mapped at cow location, we
return VM_FAULT_LOCKED despite we don't return any page from the fault.
The code in do_cow_fault() carefully handled the case when no page was
actually returned so no harm was done but still this is a bug waiting to
happen.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Patch
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diff --git a/fs/dax.c b/fs/dax.c
index 4aa440f9305b..bf39f16e5390 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -680,7 +680,9 @@  int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		if (error)
 			goto unlock_page;
 		vmf->page = page;
-		return VM_FAULT_LOCKED;
+		if (page)
+			return VM_FAULT_LOCKED;
+		return 0;
 	}
 
 	/* Check we didn't race with a read fault installing a new page */