diff options
| author | Kui-Feng Lee <kuifeng@meta.com> | 2023-01-26 16:17:32 -0800 |
|---|---|---|
| committer | Martin KaFai Lau <martin.lau@kernel.org> | 2023-01-26 23:26:40 -0800 |
| commit | 5416c9aea8323583e8696f0500b6142dfae80821 (patch) | |
| tree | d5a11ee11600569fb81abefc6611c24180a79e4d /kernel/bpf/bpf_lsm.c | |
| parent | e8c8fd9b8393d7064152c8806f5ac446d760a23e (diff) | |
| download | lwn-5416c9aea8323583e8696f0500b6142dfae80821.tar.gz lwn-5416c9aea8323583e8696f0500b6142dfae80821.zip | |
bpf: Fix the kernel crash caused by bpf_setsockopt().
The kernel crash was caused by a BPF program attached to the
"lsm_cgroup/socket_sock_rcv_skb" hook, which performed a call to
`bpf_setsockopt()` in order to set the TCP_NODELAY flag as an
example. Flags like TCP_NODELAY can prompt the kernel to flush a
socket's outgoing queue, and this hook
"lsm_cgroup/socket_sock_rcv_skb" is frequently triggered by
softirqs. The issue was that in certain circumstances, when
`tcp_write_xmit()` was called to flush the queue, it would also allow
BH (bottom-half) to run. This could lead to our program attempting to
flush the same socket recursively, which caused a `skbuff` to be
unlinked twice.
`security_sock_rcv_skb()` is triggered by `tcp_filter()`. This occurs
before the sock ownership is checked in `tcp_v4_rcv()`. Consequently,
if a bpf program runs on `security_sock_rcv_skb()` while under softirq
conditions, it may not possess the lock needed for `bpf_setsockopt()`,
thus presenting an issue.
The patch fixes this issue by ensuring that a BPF program attached to
the "lsm_cgroup/socket_sock_rcv_skb" hook is not allowed to call
`bpf_setsockopt()`.
The differences from v1 are
- changing commit log to explain holding the lock of the sock,
- emphasizing that TCP_NODELAY is not the only flag, and
- adding the fixes tag.
v1: https://lore.kernel.org/bpf/20230125000244.1109228-1-kuifeng@meta.com/
Signed-off-by: Kui-Feng Lee <kuifeng@meta.com>
Fixes: 9113d7e48e91 ("bpf: expose bpf_{g,s}etsockopt to lsm cgroup")
Link: https://lore.kernel.org/r/20230127001732.4162630-1-kuifeng@meta.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Diffstat (limited to 'kernel/bpf/bpf_lsm.c')
| -rw-r--r-- | kernel/bpf/bpf_lsm.c | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c index a4a41ee3e80b..e14c822f8911 100644 --- a/kernel/bpf/bpf_lsm.c +++ b/kernel/bpf/bpf_lsm.c @@ -51,7 +51,6 @@ BTF_SET_END(bpf_lsm_current_hooks) */ BTF_SET_START(bpf_lsm_locked_sockopt_hooks) #ifdef CONFIG_SECURITY_NETWORK -BTF_ID(func, bpf_lsm_socket_sock_rcv_skb) BTF_ID(func, bpf_lsm_sock_graft) BTF_ID(func, bpf_lsm_inet_csk_clone) BTF_ID(func, bpf_lsm_inet_conn_established) |