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authorHou Tao <houtao1@huawei.com>2023-12-04 15:04:20 +0100
committerAlexei Starovoitov <ast@kernel.org>2023-12-05 02:50:26 +0100
commit20c20bd11a0702ce4dc9300c3da58acf551d9725 (patch)
tree4ab874508a5b0c40f1f9671eaf6218ac5241fb5f /kernel/bpf/arraymap.c
parentbpf: Check rcu_read_lock_trace_held() before calling bpf map helpers (diff)
downloadlinux-20c20bd11a0702ce4dc9300c3da58acf551d9725.tar.xz
linux-20c20bd11a0702ce4dc9300c3da58acf551d9725.zip
bpf: Add map and need_defer parameters to .map_fd_put_ptr()
map is the pointer of outer map, and need_defer needs some explanation. need_defer tells the implementation to defer the reference release of the passed element and ensure that the element is still alive before the bpf program, which may manipulate it, exits. The following three cases will invoke map_fd_put_ptr() and different need_defer values will be passed to these callers: 1) release the reference of the old element in the map during map update or map deletion. The release must be deferred, otherwise the bpf program may incur use-after-free problem, so need_defer needs to be true. 2) release the reference of the to-be-added element in the error path of map update. The to-be-added element is not visible to any bpf program, so it is OK to pass false for need_defer parameter. 3) release the references of all elements in the map during map release. Any bpf program which has access to the map must have been exited and released, so need_defer=false will be OK. These two parameters will be used by the following patches to fix the potential use-after-free problem for map-in-map. Signed-off-by: Hou Tao <houtao1@huawei.com> Link: https://lore.kernel.org/r/20231204140425.1480317-3-houtao@huaweicloud.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf/arraymap.c')
-rw-r--r--kernel/bpf/arraymap.c12
1 files changed, 7 insertions, 5 deletions
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 2058e89b5ddd..f9aed5909d6e 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -867,7 +867,7 @@ int bpf_fd_array_map_update_elem(struct bpf_map *map, struct file *map_file,
}
if (old_ptr)
- map->ops->map_fd_put_ptr(old_ptr);
+ map->ops->map_fd_put_ptr(map, old_ptr, true);
return 0;
}
@@ -890,7 +890,7 @@ static long fd_array_map_delete_elem(struct bpf_map *map, void *key)
}
if (old_ptr) {
- map->ops->map_fd_put_ptr(old_ptr);
+ map->ops->map_fd_put_ptr(map, old_ptr, true);
return 0;
} else {
return -ENOENT;
@@ -913,8 +913,9 @@ static void *prog_fd_array_get_ptr(struct bpf_map *map,
return prog;
}
-static void prog_fd_array_put_ptr(void *ptr)
+static void prog_fd_array_put_ptr(struct bpf_map *map, void *ptr, bool need_defer)
{
+ /* bpf_prog is freed after one RCU or tasks trace grace period */
bpf_prog_put(ptr);
}
@@ -1239,8 +1240,9 @@ err_out:
return ee;
}
-static void perf_event_fd_array_put_ptr(void *ptr)
+static void perf_event_fd_array_put_ptr(struct bpf_map *map, void *ptr, bool need_defer)
{
+ /* bpf_perf_event is freed after one RCU grace period */
bpf_event_entry_free_rcu(ptr);
}
@@ -1294,7 +1296,7 @@ static void *cgroup_fd_array_get_ptr(struct bpf_map *map,
return cgroup_get_from_fd(fd);
}
-static void cgroup_fd_array_put_ptr(void *ptr)
+static void cgroup_fd_array_put_ptr(struct bpf_map *map, void *ptr, bool need_defer)
{
/* cgroup_put free cgrp after a rcu grace period */
cgroup_put(ptr);