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Subject[PATCH 1/1] dax: initialize variable pfn before using it
Date
Function dax_pmd_insert_mapping() contains the following code:

pfn_t pfn;
if (bdev_dax_pgoff(bdev, sector, size, &pgoff) != 0)
goto fallback;
/* ... */
fallback:
trace_dax_pmd_insert_mapping_fallback(inode, vmf, length, pfn, ret);

When the condition in the if statement fails, the function calls
trace_dax_pmd_insert_mapping_fallback() with an uninitialized pfn value.

This issue has been found while building the kernel with clang. The
compiler reported:

fs/dax.c:1280:6: error: variable 'pfn' is used uninitialized
whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
if (bdev_dax_pgoff(bdev, sector, size, &pgoff) != 0)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fs/dax.c:1310:60: note: uninitialized use occurs here
trace_dax_pmd_insert_mapping_fallback(inode, vmf, length, pfn, ret);
^~~

Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
---
fs/dax.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/dax.c b/fs/dax.c
index ab925dc6647a..20e6d76d6fff 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1283,7 +1283,7 @@ static int dax_pmd_insert_mapping(struct vm_fault *vmf, struct iomap *iomap,
void *ret = NULL, *kaddr;
long length = 0;
pgoff_t pgoff;
- pfn_t pfn;
+ pfn_t pfn = {};
int id;

if (bdev_dax_pgoff(bdev, sector, size, &pgoff) != 0)
--
2.14.1
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