diff mbox series

[v7,bpf-next,01/10] bpf: tcp: Avoid taking fast sock lock in iterator

Message ID 20230503225351.3700208-2-aditi.ghag@isovalent.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series bpf: Add socket destroy capability | expand

Checks

Context Check Description
bpf/vmtest-bpf-next-PR success PR summary
bpf/vmtest-bpf-next-VM_Test-4 fail Logs for build for aarch64 with llvm-17
bpf/vmtest-bpf-next-VM_Test-8 success Logs for set-matrix
bpf/vmtest-bpf-next-VM_Test-9 success Logs for veristat
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 28 this patch: 27
netdev/cc_maintainers fail 6 maintainers not CCed: kuba@kernel.org dsahern@kernel.org netdev@vger.kernel.org davem@davemloft.net pabeni@redhat.com edumazet@google.com
netdev/build_clang success Errors and warnings before: 8 this patch: 8
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 28 this patch: 27
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 23 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next-VM_Test-1 success Logs for ShellCheck
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bpf/vmtest-bpf-next-VM_Test-2 success Logs for build for aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-3 fail Logs for build for aarch64 with llvm-17
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bpf/vmtest-bpf-next-VM_Test-5 success Logs for build for x86_64 with gcc

Commit Message

Aditi Ghag May 3, 2023, 10:53 p.m. UTC 
Previously, BPF TCP iterator was acquiring fast version of sock lock that
disables the BH. This introduced a circular dependency with code paths that
later acquire sockets hash table bucket lock.
Replace the fast version of sock lock with slow that faciliates BPF
programs executed from the iterator to destroy TCP listening sockets
using the bpf_sock_destroy kfunc (implemened in follow-up commits).

Here is a stack trace that motivated this change:

```
lock_acquire+0xcd/0x330
_raw_spin_lock+0x33/0x40
------> sock lock acquired with BH enabled
sk_clone_lock+0x146/0x520
inet_csk_clone_lock+0x1b/0x110
tcp_create_openreq_child+0x22/0x3f0
tcp_v6_syn_recv_sock+0x96/0x940


lock_acquire+0xcd/0x330
_raw_spin_lock+0x33/0x40
------> Acquire (bucket) lhash2.lock (may cause deadlock if interrupted)
__inet_hash+0x4b/0x210
inet_csk_listen_start+0xe6/0x100
inet_listen+0x95/0x1d0
__sys_listen+0x69/0xb0
__x64_sys_listen+0x14/0x20
do_syscall_64+0x3c/0x90
entry_SYSCALL_64_after_hwframe+0x72/0xdc


lock_acquire+0xcd/0x330
_raw_spin_lock+0x33/0x40
------> Acquire (bucket) lhash2.lock
inet_unhash+0x9a/0x110
tcp_set_state+0x6a/0x210
tcp_abort+0x10d/0x200
bpf_prog_6793c5ca50c43c0d_iter_tcp6_server+0xa4/0xa9
bpf_iter_run_prog+0x1ff/0x340
------> Release (bucket) lhash2.lock
bpf_iter_tcp_seq_show+0xca/0x190
------> Acquire (bucket) lhash2.lock
------> sock lock acquired with BH disabled
bpf_seq_read+0x177/0x450

```

Acked-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Aditi Ghag <aditi.ghag@isovalent.com>
---
 net/ipv4/tcp_ipv4.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index ea370afa70ed..f2d370a9450f 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2962,7 +2962,6 @@  static int bpf_iter_tcp_seq_show(struct seq_file *seq, void *v)
 	struct bpf_iter_meta meta;
 	struct bpf_prog *prog;
 	struct sock *sk = v;
-	bool slow;
 	uid_t uid;
 	int ret;
 
@@ -2970,7 +2969,7 @@  static int bpf_iter_tcp_seq_show(struct seq_file *seq, void *v)
 		return 0;
 
 	if (sk_fullsock(sk))
-		slow = lock_sock_fast(sk);
+		lock_sock(sk);
 
 	if (unlikely(sk_unhashed(sk))) {
 		ret = SEQ_SKIP;
@@ -2994,7 +2993,7 @@  static int bpf_iter_tcp_seq_show(struct seq_file *seq, void *v)
 
 unlock:
 	if (sk_fullsock(sk))
-		unlock_sock_fast(sk, slow);
+		release_sock(sk);
 	return ret;
 
 }