ucounts: fix counter leak in inc_rlimit_get_ucounts()

The inc_rlimit_get_ucounts() increments the specified rlimit counter and
then checks its limit.  If the value exceeds the limit, the function
returns an error without decrementing the counter.

Link: https://lkml.kernel.org/r/20241101191940.3211128-1-roman.gushchin@linux.dev
Fixes: 15bc01effefe ("ucounts: Fix signal ucount refcounting")
Signed-off-by: Andrei Vagin <avagin@google.com>
Co-developed-by: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Tested-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Alexey Gladkov <legion@kernel.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Andrei Vagin <avagin@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Alexey Gladkov <legion@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/kernel/ucount.c b/kernel/ucount.c
index 8c07714ff27d42e16cf24400c6678cd691887dbd..9469102c5ac050c12f357c0fece03d4a07c6024e 100644 (file)
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -317,7 +317,7 @@ long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum rlimit_type type)
        for (iter = ucounts; iter; iter = iter->ns->ucounts) {
                long new = atomic_long_add_return(1, &iter->rlimit[type]);
                if (new < 0 || new > max)
-                       goto unwind;
+                       goto dec_unwind;
                if (iter == ucounts)
                        ret = new;
                max = get_userns_rlimit_max(iter->ns, type);
@@ -334,7 +334,6 @@ long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum rlimit_type type)
 dec_unwind:
        dec = atomic_long_sub_return(1, &iter->rlimit[type]);
        WARN_ON_ONCE(dec < 0);
-unwind:
        do_dec_rlimit_put_ucounts(ucounts, iter, type);
        return 0;
 }