diff options
| author | Petr Pavlu | 2024-07-17 15:00:23 +0200 |
|---|---|---|
| committer | Kees Cook | 2024-08-05 14:34:23 -0700 |
| commit | f91f7ac900e7342e0fd66093dfbf7cb8cb585a99 (patch) | |
| tree | 126191748ddf797d75e0ad3582f64b991295f29a /include | |
| parent | de9c2c66ad8e787abec7c9d7eff4f8c3cdd28aed (diff) | |
refcount: Report UAF for refcount_sub_and_test(0) when counter==0
When a reference counter is at zero and refcount_sub_and_test() is invoked
to subtract zero, the function accepts this request without any warning and
returns true. This behavior does not seem ideal because the counter being
already at zero indicates a use-after-free. Furthermore, returning true by
refcount_sub_and_test() in this case potentially results in a double-free
done by its caller.
Modify the underlying function __refcount_sub_and_test() to warn about this
case as a use-after-free and have it return false to avoid the potential
double-free.
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240717130023.5675-1-petr.pavlu@suse.com
Signed-off-by: Kees Cook <kees@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/refcount.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/refcount.h b/include/linux/refcount.h index 59b3b752394d..35f039ecb272 100644 --- a/include/linux/refcount.h +++ b/include/linux/refcount.h @@ -266,12 +266,12 @@ bool __refcount_sub_and_test(int i, refcount_t *r, int *oldp) if (oldp) *oldp = old; - if (old == i) { + if (old > 0 && old == i) { smp_acquire__after_ctrl_dep(); return true; } - if (unlikely(old < 0 || old - i < 0)) + if (unlikely(old <= 0 || old - i < 0)) refcount_warn_saturate(r, REFCOUNT_SUB_UAF); return false; |