linux-ext4 - [PATCH 1/2] fibmap: Warn and return an error in case of block > INT

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Date:   Fri, 24 Apr 2020 12:52:17 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     linux-fsdevel@...r.kernel.org, linux-xfs@...r.kernel.org
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        Christoph Hellwig <hch@...radead.org>,
        Jan Kara <jack@...e.com>, tytso@....edu,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        linux-ext4@...r.kernel.org, Ritesh Harjani <riteshh@...ux.ibm.com>
Subject: [PATCH 1/2] fibmap: Warn and return an error in case of block > INT_MAX

We better warn the fibmap user and not return a truncated and therefore
an incorrect block map address if the bmap() returned block address
is greater than INT_MAX (since user supplied integer pointer).

It's better to WARN all user of ioctl_fibmap() and return a proper error
code rather than silently letting a FS corruption happen if the user tries
to fiddle around with the returned block map address.

We fix this by returning an error code of -ERANGE and returning 0 as the
block mapping address in case if it is > INT_MAX.

Signed-off-by: Ritesh Harjani <riteshh@...ux.ibm.com>
---
 fs/ioctl.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/ioctl.c b/fs/ioctl.c
index f1d93263186c..3489f3a12c1d 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -71,6 +71,11 @@ static int ioctl_fibmap(struct file *filp, int __user *p)
 	block = ur_block;
 	error = bmap(inode, &block);

+	if (block > INT_MAX) {
+		error = -ERANGE;
+		WARN(1, "would truncate fibmap result\n");
+	}
+
 	if (error)
 		ur_block = 0;
 	else
-- 
2.21.0