[PATCH bpf-next 1/3] bpf: drop unnecessary bpf_capable() check in BPF_MAP_FREEZE command

[Andrii Nakryiko <andrii@kernel.org>]

Seems like that extra bpf_capable() check in BPF_MAP_FREEZE handler was
unintentionally left when we switched to a model that all BPF map
operations should be allowed regardless of CAP_BPF (or any other
capabilities), as long as process got BPF map FD somehow.

This patch replaces bpf_capable() check in BPF_MAP_FREEZE handler with
writeable access check, given conceptually freezing the map is modifying
it: map becomes unmodifiable for subsequent updates.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 kernel/bpf/syscall.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index c7f6807215e6..c9a201e4c457 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1931,6 +1931,11 @@ static int map_freeze(const union bpf_attr *attr)
 		return -ENOTSUPP;
 	}
 
+	if (!(map_get_sys_perms(map, f) & FMODE_CAN_WRITE)) {
+		err = -EPERM;
+		goto err_put;
+	}
+
 	mutex_lock(&map->freeze_mutex);
 	if (bpf_map_write_active(map)) {
 		err = -EBUSY;
@@ -1940,10 +1945,6 @@ static int map_freeze(const union bpf_attr *attr)
 		err = -EBUSY;
 		goto err_put;
 	}
-	if (!bpf_capable()) {
-		err = -EPERM;
-		goto err_put;
-	}
 
 	WRITE_ONCE(map->frozen, true);
 err_put:
-- 
2.34.1