linux-kernel - [PATCH V2] squashfs: Add length check in squashfs_symlink_read

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Message-ID: <20240801151740.339272-1-lizhi.xu@windriver.com>
Date: Thu, 1 Aug 2024 23:17:40 +0800
From: Lizhi Xu <lizhi.xu@...driver.com>
To: <viro@...iv.linux.org.uk>
CC: <brauner@...nel.org>, <jack@...e.cz>, <linux-fsdevel@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <lizhi.xu@...driver.com>,
        <phillip@...ashfs.org.uk>, <squashfs-devel@...ts.sourceforge.net>,
        <syzbot+24ac24ff58dc5b0d26b9@...kaller.appspotmail.com>,
        <syzkaller-bugs@...glegroups.com>
Subject: [PATCH V2] squashfs: Add length check in squashfs_symlink_read_folio

syzbot report KMSAN: uninit-value in pick_link, the root cause is that
squashfs_symlink_read_folio did not check the length, resulting in folio
not being initialized and did not return the corresponding error code.

The incorrect value of length is due to the incorrect value of inode->i_size.

Reported-and-tested-by: syzbot+24ac24ff58dc5b0d26b9@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=24ac24ff58dc5b0d26b9
Signed-off-by: Lizhi Xu <lizhi.xu@...driver.com>
---
 fs/squashfs/symlink.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/squashfs/symlink.c b/fs/squashfs/symlink.c
index 6ef735bd841a..d5fa5165ddd6 100644
--- a/fs/squashfs/symlink.c
+++ b/fs/squashfs/symlink.c
@@ -61,6 +61,12 @@ static int squashfs_symlink_read_folio(struct file *file, struct folio *folio)
 		}
 	}
 
+	if (length < 0) {
+		ERROR("Unable to read symlink, wrong length [%d]\n", length);
+		error = -EINVAL;
+		goto out;
+	}
+
 	/*
 	 * Read length bytes from symlink metadata.  Squashfs_read_metadata
 	 * is not used here because it can sleep and we want to use
-- 
2.43.0