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fs/ntfs3: prevent infinite loops caused by the next valid being the same

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When processing valid within the range [valid : pos), if valid cannot
be retrieved correctly, for example, if the retrieved valid value is
always the same, this can trigger a potential infinite loop, similar
to the hung problem reported by syzbot [1].

Adding a check for the valid value within the loop body, and terminating
the loop and returning -EINVAL if the value is the same as the current
value, can prevent this.

[1]
INFO: task syz.4.21:6056 blocked for more than 143 seconds.
Call Trace:
 rwbase_write_lock+0x14f/0x750 kernel/locking/rwbase_rt.c:244
 inode_lock include/linux/fs.h:1027 [inline]
 ntfs_file_write_iter+0xe6/0x870 fs/ntfs3/file.c:1284

Fixes: 4342306f0f ("fs/ntfs3: Add file operations and implementation")
Reported-by: syzbot+bcf9e1868c1a0c7e04f1@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=bcf9e1868c1a0c7e04f1
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
This commit is contained in:
Edward Adam Davis 2025-12-28 11:53:25 +08:00 committed by Konstantin Komarov
parent 1dad2fff02
commit 27b75ca4e5
No known key found for this signature in database
GPG Key ID: A9B0331F832407B6
1 changed files with 6 additions and 2 deletions
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8
fs/ntfs3/file.c
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@ -1016,8 +1016,12 @@ static ssize_t ntfs_compress_write(struct kiocb *iocb, struct iov_iter *from)
goto out;
if (lcn == SPARSE_LCN) {
ni->i_valid = valid =
frame_vbo + ((u64)clen << sbi->cluster_bits);
valid = frame_vbo + ((u64)clen << sbi->cluster_bits);
if (ni->i_valid == valid) {
err = -EINVAL;
goto out;
}
ni->i_valid = valid;
continue;
}