Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
fs/ntfs3: validate rec->used in journal-replay file record check
check_file_record() validates rec->total against the record size but never validates rec->used. The do_action() journal-replay handlers read rec->used from disk and use it to compute memmove lengths:
DeleteAttribute: memmove(attr, …, used - asize - roff) CreateAttribute: memmove(…, attr, used - roff) change_attr_size: memmove(…, used - PtrOffset(rec, next))
When rec->used is smaller than the offset of a validated attribute, or larger than the record size, these subtractions can underflow allowing us to copy huge amounts of memory in to a 4kb buffer, generally considered a bad idea overall.
This requires a corrupted filesystem, which isn’t a threat model the kernel really needs to worry about, but checking for such an obvious out-of-bounds value is good to keep things robust, especially on journal replay
Fix this up by bounding rec->used correctly.
This is much like commit b2bc7c44ed17 (“fs/ntfs3: Fix slab-out-of-bounds read in DeleteIndexEntryRoot”) which checked different values in this same switch statement.
Details
- Affected product:
- Ubuntu 20.04 ELS
- Affected packages:
- linux @ 5.4.0 (+1 more)
KernelCare state
Live-patch status from KernelCare for each operating system.
| Operating system | Status | Covered kernels |
|---|---|---|
| Amazon Linux 2023 | Planned | — |
| Debian 12 | Planned | — |
| Debian 13 | Planned | — |
| Ubuntu 22.04 | Planned | — |
| Ubuntu 24.04 | Planned | — |