This is a note to let you know that I've just added the patch titled
bpf: Acquire map uref in .init_seq_private for array map iterator
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bpf-acquire-map-uref-in-.init_seq_private-for-array-map-iterator.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From f76fa6b338055054f80c72b29c97fb95c1becadc Mon Sep 17 00:00:00 2001
From: Hou Tao <houtao1@xxxxxxxxxx>
Date: Wed, 10 Aug 2022 16:05:30 +0800
Subject: bpf: Acquire map uref in .init_seq_private for array map iterator
From: Hou Tao <houtao1@xxxxxxxxxx>
commit f76fa6b338055054f80c72b29c97fb95c1becadc upstream.
bpf_iter_attach_map() acquires a map uref, and the uref may be released
before or in the middle of iterating map elements. For example, the uref
could be released in bpf_iter_detach_map() as part of
bpf_link_release(), or could be released in bpf_map_put_with_uref() as
part of bpf_map_release().
Alternative fix is acquiring an extra bpf_link reference just like
a pinned map iterator does, but it introduces unnecessary dependency
on bpf_link instead of bpf_map.
So choose another fix: acquiring an extra map uref in .init_seq_private
for array map iterator.
Fixes: d3cc2ab546ad ("bpf: Implement bpf iterator for array maps")
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
Acked-by: Yonghong Song <yhs@xxxxxx>
Link: https://lore.kernel.org/r/20220810080538.1845898-2-houtao@xxxxxxxxxxxxxxx
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/bpf/arraymap.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -620,6 +620,11 @@ static int bpf_iter_init_array_map(void
seq_info->percpu_value_buf = value_buf;
}
+ /* bpf_iter_attach_map() acquires a map uref, and the uref may be
+ * released before or in the middle of iterating map elements, so
+ * acquire an extra map uref for iterator.
+ */
+ bpf_map_inc_with_uref(map);
seq_info->map = map;
return 0;
}
@@ -628,6 +633,7 @@ static void bpf_iter_fini_array_map(void
{
struct bpf_iter_seq_array_map_info *seq_info = priv_data;
+ bpf_map_put_with_uref(seq_info->map);
kfree(seq_info->percpu_value_buf);
}
Patches currently in stable-queue which might be from houtao1@xxxxxxxxxx are
queue-5.15/bpf-acquire-map-uref-in-.init_seq_private-for-array-map-iterator.patch
queue-5.15/bpf-acquire-map-uref-in-.init_seq_private-for-sock-map-hash-iterator.patch
queue-5.15/bpf-acquire-map-uref-in-.init_seq_private-for-hash-map-iterator.patch
queue-5.15/bpf-acquire-map-uref-in-.init_seq_private-for-sock-local-storage-map-iterator.patch
queue-5.15/bpf-check-the-validity-of-max_rdwr_access-for-sock-local-storage-map-iterator.patch
