6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Paolo Abeni pabeni@redhat.com
[ Upstream commit d109a7767273d1706b541c22b83a0323823dfde4 ]
After the blamed commit below, the MPTCP release callback can dereference the first subflow pointer via __mptcp_set_connected() and send buffer auto-tuning. Such pointer is always expected to be valid, except at socket destruction time, when the first subflow is deleted and the pointer zeroed.
If the connect event is handled by the release callback while the msk socket is finally released, MPTCP hits the following splat:
general protection fault, probably for non-canonical address 0xdffffc00000000f2: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000790-0x0000000000000797] CPU: 1 PID: 26719 Comm: syz-executor.2 Not tainted 6.6.0-syzkaller-10102-gff269e2cd5ad #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 RIP: 0010:mptcp_subflow_ctx net/mptcp/protocol.h:542 [inline] RIP: 0010:__mptcp_propagate_sndbuf net/mptcp/protocol.h:813 [inline] RIP: 0010:__mptcp_set_connected+0x57/0x3e0 net/mptcp/subflow.c:424 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff8a62323c RDX: 00000000000000f2 RSI: ffffffff8a630116 RDI: 0000000000000790 RBP: ffff88803334b100 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000034 R12: ffff88803334b198 R13: ffff888054f0b018 R14: 0000000000000000 R15: ffff88803334b100 FS: 0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fbcb4f75198 CR3: 000000006afb5000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> mptcp_release_cb+0xa2c/0xc40 net/mptcp/protocol.c:3405 release_sock+0xba/0x1f0 net/core/sock.c:3537 mptcp_close+0x32/0xf0 net/mptcp/protocol.c:3084 inet_release+0x132/0x270 net/ipv4/af_inet.c:433 inet6_release+0x4f/0x70 net/ipv6/af_inet6.c:485 __sock_release+0xae/0x260 net/socket.c:659 sock_close+0x1c/0x20 net/socket.c:1419 __fput+0x270/0xbb0 fs/file_table.c:394 task_work_run+0x14d/0x240 kernel/task_work.c:180 exit_task_work include/linux/task_work.h:38 [inline] do_exit+0xa92/0x2a20 kernel/exit.c:876 do_group_exit+0xd4/0x2a0 kernel/exit.c:1026 get_signal+0x23ba/0x2790 kernel/signal.c:2900 arch_do_signal_or_restart+0x90/0x7f0 arch/x86/kernel/signal.c:309 exit_to_user_mode_loop kernel/entry/common.c:168 [inline] exit_to_user_mode_prepare+0x11f/0x240 kernel/entry/common.c:204 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline] syscall_exit_to_user_mode+0x1d/0x60 kernel/entry/common.c:296 do_syscall_64+0x4b/0x110 arch/x86/entry/common.c:88 entry_SYSCALL_64_after_hwframe+0x63/0x6b RIP: 0033:0x7fb515e7cae9 Code: Unable to access opcode bytes at 0x7fb515e7cabf. RSP: 002b:00007fb516c560c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: 000000000000003c RBX: 00007fb515f9c120 RCX: 00007fb515e7cae9 RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000006 RBP: 00007fb515ec847a R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 000000000000006e R14: 00007fb515f9c120 R15: 00007ffc631eb968 </TASK>
To avoid sparkling unneeded conditionals, address the issue explicitly checking msk->first only in the critical place.
Fixes: 8005184fd1ca ("mptcp: refactor sndbuf auto-tuning") Cc: stable@vger.kernel.org Reported-by: syzbot+9dfbaedb6e6baca57a32@syzkaller.appspotmail.com Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/454 Reported-by: Eric Dumazet edumazet@google.com Closes: https://lore.kernel.org/netdev/CANn89iLZUA6S2a=K8GObnS62KK6Jt4B7PsAs7meMFooM... Signed-off-by: Paolo Abeni pabeni@redhat.com Reviewed-by: Eric Dumazet edumazet@google.com Reviewed-by: Mat Martineau martineau@kernel.org Signed-off-by: Matthieu Baerts matttbe@kernel.org Link: https://lore.kernel.org/r/20231114-upstream-net-20231113-mptcp-misc-fixes-6-... Signed-off-by: Jakub Kicinski kuba@kernel.org Stable-dep-of: 4fd19a307016 ("mptcp: fix inconsistent state on fastopen race") Signed-off-by: Sasha Levin sashal@kernel.org --- net/mptcp/protocol.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 44499e49d76e6..dc030551cac13 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -3397,10 +3397,11 @@ static void mptcp_release_cb(struct sock *sk) if (__test_and_clear_bit(MPTCP_CLEAN_UNA, &msk->cb_flags)) __mptcp_clean_una_wakeup(sk); if (unlikely(msk->cb_flags)) { - /* be sure to set the current sk state before tacking actions - * depending on sk_state, that is processing MPTCP_ERROR_REPORT + /* be sure to set the current sk state before taking actions + * depending on sk_state (MPTCP_ERROR_REPORT) + * On sk release avoid actions depending on the first subflow */ - if (__test_and_clear_bit(MPTCP_CONNECTED, &msk->cb_flags)) + if (__test_and_clear_bit(MPTCP_CONNECTED, &msk->cb_flags) && msk->first) __mptcp_set_connected(sk); if (__test_and_clear_bit(MPTCP_ERROR_REPORT, &msk->cb_flags)) __mptcp_error_report(sk);