Description

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

bpf: avoid holding freeze_mutex during mmap operation

We use map->freeze_mutex to prevent races between map_freeze() and
memory mapping BPF map contents with writable permissions. The way we
naively do this means we'll hold freeze_mutex for entire duration of all
the mm and VMA manipulations, which is completely unnecessary. This can
potentially also lead to deadlocks, as reported by syzbot in [0].

So, instead, hold freeze_mutex only during writeability checks, bump
(proactively) "write active" count for the map, unlock the mutex and
proceed with mmap logic. And only if something went wrong during mmap
logic, then undo that "write active" counter increment.

[0] https://lore.kernel.org/bpf/[email protected]/

Classification

CVE ID: CVE-2025-21853

Affected Products

Vendor: Linux, Linux

Product: Linux, Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.02% (probability of being exploited)

EPSS Percentile: 1.79% (scored less or equal to compared to others)

EPSS Date: 2025-04-10 (when was this score calculated)

References

https://nvd.nist.gov/vuln/detail/CVE-2025-21853
https://git.kernel.org/stable/c/29cfda62ab4d92ab94123813db49ab76c1e61b29
https://git.kernel.org/stable/c/d95607a5f2f9bb08194c9deaf4a5f3e8ba59a9d4
https://git.kernel.org/stable/c/271e49f8a58edba65bc2b1250a0abaa98c4bfdbe
https://git.kernel.org/stable/c/bc27c52eea189e8f7492d40739b7746d67b65beb

Timeline