xen/privcmd: Fix a possible warning in privcmd_ioctl_mmap_resource()

[PATCH] xen/privcmd: Fix a possible warning in privcmd_ioctl_mmap_resource()

Posted by Harshit Mogalapalli 1 year, 4 months ago

As 'kdata.num' is user-controlled data, if user tries to allocate
memory larger than(>=) MAX_ORDER, then kcalloc() will fail, it
creates a stack trace and messes up dmesg with a warning.

Call trace:
-> privcmd_ioctl
--> privcmd_ioctl_mmap_resource

Add __GFP_NOWARN in order to avoid too large allocation warning.
This is detected by static analysis using smatch.

Fixes: 3ad0876554ca ("xen/privcmd: add IOCTL_PRIVCMD_MMAP_RESOURCE")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
---
 drivers/xen/privcmd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index fae50a24630b..1edf45ee9890 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -760,7 +760,7 @@ static long privcmd_ioctl_mmap_resource(struct file *file,
 		goto out;
 	}
 
-	pfns = kcalloc(kdata.num, sizeof(*pfns), GFP_KERNEL);
+	pfns = kcalloc(kdata.num, sizeof(*pfns), GFP_KERNEL | __GFP_NOWARN);
 	if (!pfns) {
 		rc = -ENOMEM;
 		goto out;
-- 
2.38.1

Re: [PATCH] xen/privcmd: Fix a possible warning in privcmd_ioctl_mmap_resource()

Posted by Juergen Gross 1 year, 4 months ago

On 26.11.22 06:07, Harshit Mogalapalli wrote:
> As 'kdata.num' is user-controlled data, if user tries to allocate
> memory larger than(>=) MAX_ORDER, then kcalloc() will fail, it
> creates a stack trace and messes up dmesg with a warning.
> 
> Call trace:
> -> privcmd_ioctl
> --> privcmd_ioctl_mmap_resource
> 
> Add __GFP_NOWARN in order to avoid too large allocation warning.
> This is detected by static analysis using smatch.
> 
> Fixes: 3ad0876554ca ("xen/privcmd: add IOCTL_PRIVCMD_MMAP_RESOURCE")
> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen