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authorJakub Sitnicki <jakub@cloudflare.com>2024-04-02 12:46:21 +0200
committerDaniel Borkmann <daniel@iogearbox.net>2024-04-02 16:31:05 +0200
commitff91059932401894e6c86341915615c5eb0eca48 (patch)
tree2a7b401e3f18c6df1de80a3833228250aaaa9211 /net
parent8c3fe029d79ada599fa558fdf3da0322fc38de36 (diff)
bpf, sockmap: Prevent lock inversion deadlock in map delete elem
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
Diffstat (limited to 'net')
-rw-r--r--net/core/sock_map.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 27d733c0f65e..8598466a3805 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -411,6 +411,9 @@ static int __sock_map_delete(struct bpf_stab *stab, struct sock *sk_test,
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 bpf_map *map, void *key)
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);