6.6-stable review patch. If anyone has any objections, please let me know.
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From: Jakub Sitnicki jakub@cloudflare.com
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@gmail.com Reported-by: yue sun samsun1006219@gmail.com Reported-by: syzbot+bc922f476bd65abbd466@syzkaller.appspotmail.com Reported-by: syzbot+d4066896495db380182e@syzkaller.appspotmail.com Signed-off-by: Jakub Sitnicki jakub@cloudflare.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Tested-by: syzbot+d4066896495db380182e@syzkaller.appspotmail.com Acked-by: John Fastabend john.fastabend@gmail.com 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@cloudflare.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/core/sock_map.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/net/core/sock_map.c +++ b/net/core/sock_map.c @@ -411,6 +411,9 @@ static int __sock_map_delete(struct bpf_ struct sock *sk; int err = 0;
+ if (irqs_disabled()) + return -EOPNOTSUPP; /* locks here are hardirq-unsafe */ + spin_lock_bh(&stab->lock); sk = *psk; if (!sk_test || sk_test == sk) @@ -933,6 +936,9 @@ static long sock_hash_delete_elem(struct struct bpf_shtab_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);