🛡️ CVE-2025-71265 — kernel

fs: ntfs3: fix infinite loop in attr_load_runs_range on inconsistent metadata

In the Linux kernel, the following vulnerability has been resolved:

fs: ntfs3: fix infinite loop in attr_load_runs_range on inconsistent metadata

We found an infinite loop bug in the ntfs3 file system that can lead to a

Denial-of-Service (DoS) condition.

A malformed NTFS image can cause an infinite loop when an attribute header

indicates an empty run list, while directory entries reference it as

containing actual data. In NTFS, setting evcn=-1 with svcn=0 is a valid way

to represent an empty run list, and run_unpack() correctly handles this by

checking if evcn + 1 equals svcn and returning early without parsing any run

data. However, this creates a problem when there is metadata inconsistency,

where the attribute header claims to be empty (evcn=-1) but the caller

expects to read actual data. When run_unpack() immediately returns success

upon seeing this condition, it leaves the runs_tree uninitialized with

run->runs as a NULL. The calling function attr_load_runs_range() assumes

that a successful return means that the runs were loaded and sets clen to 0,

expecting the next run_lookup_entry() call to succeed. Because runs_tree

remains uninitialized, run_lookup_entry() continues to fail, and the loop

increments vcn by zero (vcn += 0), leading to an infinite loop.

This patch adds a retry counter to detect when run_lookup_entry() fails

consecutively after attr_load_runs_vcn(). If the run is still not found on

the second attempt, it indicates corrupted metadata and returns -EINVAL,

preventing the Denial-of-Service (DoS) vulnerability.