This is a note to let you know that I've just added the patch titled
bpf: fix rcu lockdep warning for lpm_trie map_free callback
to the 4.15-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-fix-rcu-lockdep-warning-for-lpm_trie-map_free-callback.patch
and it can be found in the queue-4.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Fri Mar 9 14:15:30 PST 2018
From: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Date: Thu, 8 Mar 2018 13:16:44 +0100
Subject: bpf: fix rcu lockdep warning for lpm_trie map_free callback
To: gregkh@xxxxxxxxxxxxxxxxxxx
Cc: ast@xxxxxxxxxx, daniel@xxxxxxxxxxxxx, stable@xxxxxxxxxxxxxxx, Yonghong Song <yhs@xxxxxx>
Message-ID: <3181ff4299652cbcfec7f1f2632ce1e486a3a25a.1520507630.git.daniel@xxxxxxxxxxxxx>
From: Yonghong Song <yhs@xxxxxx>
[ upstream commit 6c5f61023c5b0edb0c8a64c902fe97c6453b1852 ]
Commit 9a3efb6b661f ("bpf: fix memory leak in lpm_trie map_free callback function")
fixed a memory leak and removed unnecessary locks in map_free callback function.
Unfortrunately, it introduced a lockdep warning. When lockdep checking is turned on,
running tools/testing/selftests/bpf/test_lpm_map will have:
[ 98.294321] =============================
[ 98.294807] WARNING: suspicious RCU usage
[ 98.295359] 4.16.0-rc2+ #193 Not tainted
[ 98.295907] -----------------------------
[ 98.296486] /home/yhs/work/bpf/kernel/bpf/lpm_trie.c:572 suspicious rcu_dereference_check() usage!
[ 98.297657]
[ 98.297657] other info that might help us debug this:
[ 98.297657]
[ 98.298663]
[ 98.298663] rcu_scheduler_active = 2, debug_locks = 1
[ 98.299536] 2 locks held by kworker/2:1/54:
[ 98.300152] #0: ((wq_completion)"events"){+.+.}, at: [<00000000196bc1f0>] process_one_work+0x157/0x5c0
[ 98.301381] #1: ((work_completion)(&map->work)){+.+.}, at: [<00000000196bc1f0>] process_one_work+0x157/0x5c0
Since actual trie tree removal happens only after no other
accesses to the tree are possible, replacing
rcu_dereference_protected(*slot, lockdep_is_held(&trie->lock))
with
rcu_dereference_protected(*slot, 1)
fixed the issue.
Fixes: 9a3efb6b661f ("bpf: fix memory leak in lpm_trie map_free callback function")
Reported-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Suggested-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: Yonghong Song <yhs@xxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Acked-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/bpf/lpm_trie.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -574,8 +574,7 @@ static void trie_free(struct bpf_map *ma
slot = &trie->root;
for (;;) {
- node = rcu_dereference_protected(*slot,
- lockdep_is_held(&trie->lock));
+ node = rcu_dereference_protected(*slot, 1);
if (!node)
goto out;
Patches currently in stable-queue which might be from daniel@xxxxxxxxxxxxx are
queue-4.15/bpf-fix-mlock-precharge-on-arraymaps.patch
queue-4.15/bpf-x64-implement-retpoline-for-tail-call.patch
queue-4.15/bpf-arm64-fix-out-of-bounds-access-in-tail-call.patch
queue-4.15/bpf-fix-memory-leak-in-lpm_trie-map_free-callback-function.patch
queue-4.15/bpf-ppc64-fix-out-of-bounds-access-in-tail-call.patch
queue-4.15/bpf-add-schedule-points-in-percpu-arrays-management.patch
queue-4.15/bpf-allow-xadd-only-on-aligned-memory.patch
queue-4.15/bpf-fix-rcu-lockdep-warning-for-lpm_trie-map_free-callback.patch