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authorToshiaki Makita <toshiaki.makita1@gmail.com>2019-06-14 17:20:13 +0900
committerDaniel Borkmann <daniel@iogearbox.net>2019-06-15 00:58:42 +0200
commitd4dd153d551634683fccf8881f606fa9f3dfa1ef (patch)
treed22755648032058eb1fd16f29eb58d32ce5ad683
parent09f6ac2c31f391f754a7bd382e4c0a378662f998 (diff)
bpf, devmap: Fix premature entry free on destroying map
dev_map_free() waits for flush_needed bitmap to be empty in order to ensure all flush operations have completed before freeing its entries. However the corresponding clear_bit() was called before using the entries, so the entries could be used after free. All access to the entries needs to be done before clearing the bit. It seems commit a5e2da6e9787 ("bpf: netdev is never null in __dev_map_flush") accidentally changed the clear_bit() and memory access order. Note that the problem happens only in __dev_map_flush(), not in dev_map_flush_old(). dev_map_flush_old() is called only after nulling out the corresponding netdev_map entry, so dev_map_free() never frees the entry thus no such race happens there. Fixes: a5e2da6e9787 ("bpf: netdev is never null in __dev_map_flush") Signed-off-by: Toshiaki Makita <toshiaki.makita1@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
-rw-r--r--kernel/bpf/devmap.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 1e525d70f833..e001fb1a96b1 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -291,10 +291,10 @@ void __dev_map_flush(struct bpf_map *map)
if (unlikely(!dev))
continue;
- __clear_bit(bit, bitmap);
-
bq = this_cpu_ptr(dev->bulkq);
bq_xmit_all(dev, bq, XDP_XMIT_FLUSH, true);
+
+ __clear_bit(bit, bitmap);
}
}