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Subject[PATCH] xen/privcmd: fix static checker warning
Date
Commit 3ad0876554ca ("xen/privcmd: add IOCTL_PRIVCMD_MMAP_RESOURCE")
introduced a static checker warning:

drivers/xen/privcmd.c:827 privcmd_ioctl_mmap_resource()
warn: passing casted pointer 'pfns' to 'xen_remap_domain_mfn_array()'
64 vs 32.

caused by this cast:

827 num = xen_remap_domain_mfn_array(vma,
828 kdata.addr & PAGE_MASK,
829 pfns, kdata.num, (int *)pfns,
^^^^^^^^^^^

The reason for the cast is that xen_remap_domain_mfn_array() requires an
array of ints to store error codes. It is actually safe to re-use the
pfns array for this purpose but it does look odd (as well as leading to
the warning). It would also be easy for a future implementation change
to make this re-use unsafe so this patch modifies privcmd to use a
separately allocated array for error codes.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
---
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
---
drivers/xen/privcmd.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index 8ae0349..8507c13 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -822,11 +822,18 @@ static long privcmd_ioctl_mmap_resource(struct file *file, void __user *udata)
unsigned int domid =
(xdata.flags & XENMEM_rsrc_acq_caller_owned) ?
DOMID_SELF : kdata.dom;
+ int *errs;
int num;

+ errs = kcalloc(kdata.num, sizeof(*errs), GFP_KERNEL);
+ if (!errs) {
+ rc = -ENOMEM;
+ goto out;
+ }
+
num = xen_remap_domain_mfn_array(vma,
kdata.addr & PAGE_MASK,
- pfns, kdata.num, (int *)pfns,
+ pfns, kdata.num, errs,
vma->vm_page_prot,
domid,
vma->vm_private_data);
@@ -836,12 +843,14 @@ static long privcmd_ioctl_mmap_resource(struct file *file, void __user *udata)
unsigned int i;

for (i = 0; i < num; i++) {
- rc = pfns[i];
+ rc = errs[i];
if (rc < 0)
break;
}
} else
rc = 0;
+
+ kfree(errs);
}

out:
--
2.1.4
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