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b2c5b614ca
syzbot triggered following lockdep splat:
ffffffff82d2cd40 (rtnl_mutex){+.+.}, at: ip_mc_drop_socket+0x52/0x180
but task is already holding lock:
ffff8881187a2310 (sk_lock-AF_INET){+.+.}, at: mptcp_close+0x18/0x30
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (sk_lock-AF_INET){+.+.}:
lock_acquire+0xee/0x230
lock_sock_nested+0x89/0xc0
do_ip_setsockopt.isra.0+0x335/0x22f0
ip_setsockopt+0x35/0x60
tcp_setsockopt+0x5d/0x90
__sys_setsockopt+0xf3/0x190
__x64_sys_setsockopt+0x61/0x70
do_syscall_64+0x72/0x300
entry_SYSCALL_64_after_hwframe+0x49/0xbe
-> #0 (rtnl_mutex){+.+.}:
check_prevs_add+0x2b7/0x1210
__lock_acquire+0x10b6/0x1400
lock_acquire+0xee/0x230
__mutex_lock+0x120/0xc70
ip_mc_drop_socket+0x52/0x180
inet_release+0x36/0xe0
__sock_release+0xfd/0x130
__mptcp_close+0xa8/0x1f0
inet_release+0x7f/0xe0
__sock_release+0x69/0x130
sock_close+0x18/0x20
__fput+0x179/0x400
task_work_run+0xd5/0x110
do_exit+0x685/0x1510
do_group_exit+0x7e/0x170
__x64_sys_exit_group+0x28/0x30
do_syscall_64+0x72/0x300
entry_SYSCALL_64_after_hwframe+0x49/0xbe
The trigger is:
socket(AF_INET, SOCK_STREAM, 0x106 /* IPPROTO_MPTCP */) = 4
setsockopt(4, SOL_IP, MCAST_JOIN_GROUP, {gr_interface=7, gr_group={sa_family=AF_INET, sin_port=htons(20003), sin_addr=inet_addr("224.0.0.2")}}, 136) = 0
exit(0)
Which results in a call to rtnl_lock while we are holding
the parent mptcp socket lock via
mptcp_close -> lock_sock(msk) -> inet_release -> ip_mc_drop_socket -> rtnl_lock().
>From lockdep point of view we thus have both
'rtnl_lock; lock_sock' and 'lock_sock; rtnl_lock'.
Fix this by stealing the msk conn_list and doing the subflow close
without holding the msk lock.
Fixes:
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||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.