[PATCH 1/1] libxl: Fix uninitialized pointer when passing an empty cdrom

[PATCH 1/1] libxl: Fix uninitialized pointer when passing an empty cdrom

[George Dunlap]

Commit 3fec17d4bb56567d139d7806392f4d8702d3f6a7 introduced a bug where
an empty cdrom would cause target_path to be uninitialized.  Initialize
target_path to NULL instead.

The other option here would have been to set target_path to NULL only
on the LIBXL_DISK_FORMAT_EMPTY path.  That would potentially enable
the compiler to catch future uninitialized paths, rather than having
those paths (potentially) dereference a NULL pointer.  But given that
a bunch of our compilers failed to catch *this* uninitialized path,
setting it to NULL at declaration seems the safer option for now.

Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: George Dunlap <george.dunlap@citrix.com>
---
CC: Ian Jackson <ian.jackson@citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Andrew Cooper <andrew.cooper3@citrix.com>
---
 tools/libxl/libxl_dm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 5b79aa2..eac5501 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -1307,7 +1307,7 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
                 libxl__device_disk_dev_number(disks[i].vdev, &disk, &part);
             const char *format;
             char *drive;
-            const char *target_path;
+            const char *target_path = NULL;
             int colo_mode;
 
             if (dev_number == -1) {
-- 
2.1.4


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Re: [PATCH 1/1] libxl: Fix uninitialized pointer when passing an empty cdrom

[Andrew Cooper]

On 06/04/16 12:34, George Dunlap wrote:
> Commit 3fec17d4bb56567d139d7806392f4d8702d3f6a7 introduced a bug where
> an empty cdrom would cause target_path to be uninitialized.  Initialize
> target_path to NULL instead.
>
> The other option here would have been to set target_path to NULL only
> on the LIBXL_DISK_FORMAT_EMPTY path.  That would potentially enable
> the compiler to catch future uninitialized paths, rather than having
> those paths (potentially) dereference a NULL pointer.  But given that
> a bunch of our compilers failed to catch *this* uninitialized path,
> setting it to NULL at declaration seems the safer option for now.
>
> Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Signed-off-by: George Dunlap <george.dunlap@citrix.com>

This looks like it will work.  Reviewed-by: Andrew Cooper
<andrew.cooper3@citrix.com>

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Re: [PATCH 1/1] libxl: Fix uninitialized pointer when passing an empty cdrom

[Ian Jackson]

Andrew Cooper writes ("Re: [PATCH 1/1] libxl: Fix uninitialized pointer when passing an empty cdrom"):
> On 06/04/16 12:34, George Dunlap wrote:
> > Commit 3fec17d4bb56567d139d7806392f4d8702d3f6a7 introduced a bug where
> > an empty cdrom would cause target_path to be uninitialized.  Initialize
> > target_path to NULL instead.
> >
> > The other option here would have been to set target_path to NULL only
> > on the LIBXL_DISK_FORMAT_EMPTY path.  That would potentially enable
> > the compiler to catch future uninitialized paths, rather than having
> > those paths (potentially) dereference a NULL pointer.  But given that
> > a bunch of our compilers failed to catch *this* uninitialized path,
> > setting it to NULL at declaration seems the safer option for now.

This reasoning is plausible.

> > Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
> > Signed-off-by: George Dunlap <george.dunlap@citrix.com>
> 
> This looks like it will work.  Reviewed-by: Andrew Cooper
> <andrew.cooper3@citrix.com>

Thanks.  Queued.

Ian.

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