diff options
| author | Kees Cook <[email protected]> | 2024-05-03 13:16:25 -0700 |
|---|---|---|
| committer | Christian Brauner <[email protected]> | 2024-05-04 11:42:01 +0200 |
| commit | f6bdc7865ef4a7a4393c90a550c728231ebc853e (patch) | |
| tree | 133b569d8c2042107a36bb5608ee8f3ef726d838 | |
| parent | e035af9f6ebacd98774b1be2af58a5afd6d0d291 (diff) | |
fs: WARN when f_count resurrection is attempted
It should never happen that get_file() is called on a file with
f_count equal to zero. If this happens, a use-after-free condition
has happened[1], and we need to attempt a best-effort reporting of
the situation to help find the root cause more easily. Additionally,
this serves as a data corruption indicator that system owners using
warn_limit or panic_on_warn would like to have detected.
Link: https://lore.kernel.org/lkml/[email protected]/ [1]
Suggested-by: Peter Zijlstra <[email protected]>
Signed-off-by: Kees Cook <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>
| -rw-r--r-- | include/linux/fs.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h index e5f643e97cfd..5b351c1e6f58 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1034,7 +1034,8 @@ struct file_handle { static inline struct file *get_file(struct file *f) { - atomic_long_inc(&f->f_count); + long prior = atomic_long_fetch_inc_relaxed(&f->f_count); + WARN_ONCE(!prior, "struct file::f_count incremented from zero; use-after-free condition present!\n"); return f; } |