This is a note to let you know that I've just added the patch titled
bpf, sockmap: Prevent lock inversion deadlock in map delete elem
to the 5.4-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-sockmap-prevent-lock-inversion-deadlock-in-map-delete-elem.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ff91059932401894e6c86341915615c5eb0eca48 Mon Sep 17 00:00:00 2001
From: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
Date: Tue, 2 Apr 2024 12:46:21 +0200
Subject: bpf, sockmap: Prevent lock inversion deadlock in map delete elem
From: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
commit ff91059932401894e6c86341915615c5eb0eca48 upstream.
syzkaller started using corpuses where a BPF tracing program deletes
elements from a sockmap/sockhash map. Because BPF tracing programs can be
invoked from any interrupt context, locks taken during a map_delete_elem
operation must be hardirq-safe. Otherwise a deadlock due to lock inversion
is possible, as reported by lockdep:
CPU0 CPU1
---- ----
lock(&htab->buckets[i].lock);
local_irq_disable();
lock(&host->lock);
lock(&htab->buckets[i].lock);
<Interrupt>
lock(&host->lock);
Locks in sockmap are hardirq-unsafe by design. We expects elements to be
deleted from sockmap/sockhash only in task (normal) context with interrupts
enabled, or in softirq context.
Detect when map_delete_elem operation is invoked from a context which is
_not_ hardirq-unsafe, that is interrupts are disabled, and bail out with an
error.
Note that map updates are not affected by this issue. BPF verifier does not
allow updating sockmap/sockhash from a BPF tracing program today.
Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
Reported-by: xingwei lee <xrivendell7@xxxxxxxxx>
Reported-by: yue sun <samsun1006219@xxxxxxxxx>
Reported-by: syzbot+bc922f476bd65abbd466@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: syzbot+d4066896495db380182e@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Tested-by: syzbot+d4066896495db380182e@xxxxxxxxxxxxxxxxxxxxxxxxx
Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
Closes: https://syzkaller.appspot.com/bug?extid=d4066896495db380182e
Closes: https://syzkaller.appspot.com/bug?extid=bc922f476bd65abbd466
Link: https://lore.kernel.org/bpf/20240402104621.1050319-1-jakub@xxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/core/sock_map.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -321,6 +321,9 @@ static int __sock_map_delete(struct bpf_
struct sock *sk;
int err = 0;
+ if (irqs_disabled())
+ return -EOPNOTSUPP; /* locks here are hardirq-unsafe */
+
raw_spin_lock_bh(&stab->lock);
sk = *psk;
if (!sk_test || sk_test == sk)
@@ -654,6 +657,9 @@ static int sock_hash_delete_elem(struct
struct bpf_htab_elem *elem;
int ret = -ENOENT;
+ if (irqs_disabled())
+ return -EOPNOTSUPP; /* locks here are hardirq-unsafe */
+
hash = sock_hash_bucket_hash(key, key_size);
bucket = sock_hash_select_bucket(htab, hash);
Patches currently in stable-queue which might be from jakub@xxxxxxxxxxxxxx are
queue-5.4/bpf-sockmap-prevent-lock-inversion-deadlock-in-map-delete-elem.patch
