From 29d650f7e3ab55283b89c9f5883d0c256ce478b5 Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <djwong@kernel.org>
Date: Mon, 24 Jan 2022 15:48:31 -0800
Subject: [PATCH] xfs: reject crazy array sizes being fed to XFS_IOC_GETBMAP*
Git-commit: 29d650f7e3ab55283b89c9f5883d0c256ce478b5
Patch-mainline: v5.17-rc3
References: git-fixes

Syzbot tripped over the following complaint from the kernel:

Warning: CPU: 2 PID: 15402 at mm/util.c:597 kvmalloc_node+0x11e/0x125 mm/util.c:597

While trying to run XFS_IOC_GETBMAP against the following structure:

struct getbmap fubar = {
	.bmv_count	= 0x22dae649,
};

Obviously, this is a crazy huge value since the next thing that the
ioctl would do is allocate 37GB of memory.  This is enough to make
kvmalloc mad, but isn't large enough to trip the validation functions.
In other words, I'm fussing with checks that were **already sufficient**
because that's easier than dealing with 644 internal bug reports.  Yes,
that's right, six hundred and forty-four.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Catherine Hoang <catherine.hoang@oracle.com>
Acked-by: Anthony Iliopoulos <ailiop@suse.com>

---
 fs/xfs/xfs_ioctl.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1546,7 +1546,7 @@ xfs_ioc_getbmap(
 
 	if (bmx.bmv_count < 2)
 		return -EINVAL;
-	if (bmx.bmv_count > ULONG_MAX / recsize)
+	if (bmx.bmv_count >= INT_MAX / recsize)
 		return -ENOMEM;
 
 	buf = kvzalloc(bmx.bmv_count * sizeof(*buf), GFP_KERNEL);