linux-kernel - [PATCH 5/6] fs/ntfs3: Additional check in ntfs_file

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Message-ID: <20241001090104.15313-6-almaz.alexandrovich@paragon-software.com>
Date: Tue, 1 Oct 2024 12:01:03 +0300
From: Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
To: <ntfs3@...ts.linux.dev>
CC: <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
	Konstantin Komarov <almaz.alexandrovich@...agon-software.com>,
	<syzbot+8c652f14a0fde76ff11d@...kaller.appspotmail.com>
Subject: [PATCH 5/6] fs/ntfs3: Additional check in ntfs_file_release

Reported-by: syzbot+8c652f14a0fde76ff11d@...kaller.appspotmail.com
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
---
 fs/ntfs3/file.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/ntfs3/file.c b/fs/ntfs3/file.c
index 4fdcb5177ea1..eb935d4180c0 100644
--- a/fs/ntfs3/file.c
+++ b/fs/ntfs3/file.c
@@ -1314,7 +1314,14 @@ static int ntfs_file_release(struct inode *inode, struct file *file)
 	/* If we are last writer on the inode, drop the block reservation. */
 	if (sbi->options->prealloc &&
 	    ((file->f_mode & FMODE_WRITE) &&
-	     atomic_read(&inode->i_writecount) == 1)) {
+	     atomic_read(&inode->i_writecount) == 1)
+	   /*
+	    * The only file when inode->i_fop = &ntfs_file_operations and
+	    * init_rwsem(&ni->file.run_lock) is not called explicitly is MFT.
+	    *
+	    * Add additional check here.
+	    */
+	    && inode->i_ino != MFT_REC_MFT) {
 		ni_lock(ni);
 		down_write(&ni->file.run_lock);
 
-- 
2.34.1