linux-kernel - [PATCH 5.4 05/22] btrfs: validate qgroup inherit for SNAP_CREATE

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Date:   Mon,  8 Mar 2021 13:30:22 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dan Carpenter <dan.carpenter@...cle.com>,
        David Sterba <dsterba@...e.com>
Subject: [PATCH 5.4 05/22] btrfs: validate qgroup inherit for SNAP_CREATE_V2 ioctl

From: Dan Carpenter <dancarpenter@...cle.com>

commit 5011c5a663b9c6d6aff3d394f11049b371199627 upstream.

The problem is we're copying "inherit" from user space but we don't
necessarily know that we're copying enough data for a 64 byte
struct.  Then the next problem is that 'inherit' has a variable size
array at the end, and we have to verify that array is the size we
expected.

Fixes: 6f72c7e20dba ("Btrfs: add qgroup inheritance")
CC: stable@...r.kernel.org # 4.4+
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Reviewed-by: David Sterba <dsterba@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/btrfs/ioctl.c |   19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1907,7 +1907,10 @@ static noinline int btrfs_ioctl_snap_cre
 	if (vol_args->flags & BTRFS_SUBVOL_RDONLY)
 		readonly = true;
 	if (vol_args->flags & BTRFS_SUBVOL_QGROUP_INHERIT) {
-		if (vol_args->size > PAGE_SIZE) {
+		u64 nums;
+
+		if (vol_args->size < sizeof(*inherit) ||
+		    vol_args->size > PAGE_SIZE) {
 			ret = -EINVAL;
 			goto free_args;
 		}
@@ -1916,6 +1919,20 @@ static noinline int btrfs_ioctl_snap_cre
 			ret = PTR_ERR(inherit);
 			goto free_args;
 		}
+
+		if (inherit->num_qgroups > PAGE_SIZE ||
+		    inherit->num_ref_copies > PAGE_SIZE ||
+		    inherit->num_excl_copies > PAGE_SIZE) {
+			ret = -EINVAL;
+			goto free_inherit;
+		}
+
+		nums = inherit->num_qgroups + 2 * inherit->num_ref_copies +
+		       2 * inherit->num_excl_copies;
+		if (vol_args->size != struct_size(inherit, qgroups, nums)) {
+			ret = -EINVAL;
+			goto free_inherit;
+		}
 	}
 
 	ret = btrfs_ioctl_snap_create_transid(file, vol_args->name,