linux-kernel - [PATCH] xen/privcmd: Fix a possible warning in privcmd_ioctl_mmap

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Date:   Fri, 25 Nov 2022 21:07:45 -0800
From:   Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     harshit.m.mogalapalli@...cle.com, error27@...il.com,
        harshit.m.mogalapalli@...il.com, Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        Paul Durrant <paul.durrant@...rix.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Subject: [PATCH] xen/privcmd: Fix a possible warning in privcmd_ioctl_mmap_resource()

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@...cle.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