forked from Minki/linux
mainlining shenanigans
0a889b9404
a recursive lock warning [1] can be observed with the following script, # $TC actions add action ife encode allow prio pass index 42 IFE type 0xED3E # $TC actions replace action ife encode allow tcindex pass index 42 in case the kernel was unable to run the last command (e.g. because of the impossibility to load 'act_meta_skbtcindex'). For a similar reason, the kernel can leak idr in the error path of tcf_ife_init(), because tcf_idr_release() is not called after successful idr reservation: # $TC actions add action ife encode allow tcindex index 47 IFE type 0xED3E RTNETLINK answers: No such file or directory We have an error talking to the kernel # $TC actions add action ife encode allow tcindex index 47 IFE type 0xED3E RTNETLINK answers: No space left on device We have an error talking to the kernel # $TC actions add action ife encode use mark 7 type 0xfefe pass index 47 IFE type 0xFEFE RTNETLINK answers: No space left on device We have an error talking to the kernel Since tcfa_lock is already taken when the action is being edited, a call to tcf_idr_release() wrongly makes tcf_idr_cleanup() take the same lock again. On the other hand, tcf_idr_release() needs to be called in the error path of tcf_ife_init(), to undo the last tcf_idr_create() invocation. Fix both problems in tcf_ife_init(). Since the cleanup() routine can now be called when ife->params is NULL, also add a NULL pointer check to avoid calling kfree_rcu(NULL, rcu). [1] ============================================ WARNING: possible recursive locking detected 4.17.0-rc4.kasan+ #417 Tainted: G E -------------------------------------------- tc/3932 is trying to acquire lock: 000000005097c9a6 (&(&p->tcfa_lock)->rlock){+...}, at: tcf_ife_cleanup+0x19/0x80 [act_ife] but task is already holding lock: 000000005097c9a6 (&(&p->tcfa_lock)->rlock){+...}, at: tcf_ife_init+0xf6d/0x13c0 [act_ife] other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&(&p->tcfa_lock)->rlock); lock(&(&p->tcfa_lock)->rlock); *** DEADLOCK *** May be due to missing lock nesting notation 2 locks held by tc/3932: #0: 000000007ca8e990 (rtnl_mutex){+.+.}, at: tcf_ife_init+0xf61/0x13c0 [act_ife] #1: 000000005097c9a6 (&(&p->tcfa_lock)->rlock){+...}, at: tcf_ife_init+0xf6d/0x13c0 [act_ife] stack backtrace: CPU: 3 PID: 3932 Comm: tc Tainted: G E 4.17.0-rc4.kasan+ #417 Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 Call Trace: dump_stack+0x9a/0xeb __lock_acquire+0xf43/0x34a0 ? debug_check_no_locks_freed+0x2b0/0x2b0 ? debug_check_no_locks_freed+0x2b0/0x2b0 ? debug_check_no_locks_freed+0x2b0/0x2b0 ? __mutex_lock+0x62f/0x1240 ? kvm_sched_clock_read+0x1a/0x30 ? sched_clock+0x5/0x10 ? sched_clock_cpu+0x18/0x170 ? find_held_lock+0x39/0x1d0 ? lock_acquire+0x10b/0x330 lock_acquire+0x10b/0x330 ? tcf_ife_cleanup+0x19/0x80 [act_ife] _raw_spin_lock_bh+0x38/0x70 ? tcf_ife_cleanup+0x19/0x80 [act_ife] tcf_ife_cleanup+0x19/0x80 [act_ife] __tcf_idr_release+0xff/0x350 tcf_ife_init+0xdde/0x13c0 [act_ife] ? ife_exit_net+0x290/0x290 [act_ife] ? __lock_is_held+0xb4/0x140 tcf_action_init_1+0x67b/0xad0 ? tcf_action_dump_old+0xa0/0xa0 ? sched_clock+0x5/0x10 ? sched_clock_cpu+0x18/0x170 ? kvm_sched_clock_read+0x1a/0x30 ? sched_clock+0x5/0x10 ? sched_clock_cpu+0x18/0x170 ? memset+0x1f/0x40 tcf_action_init+0x30f/0x590 ? tcf_action_init_1+0xad0/0xad0 ? memset+0x1f/0x40 tc_ctl_action+0x48e/0x5e0 ? mutex_lock_io_nested+0x1160/0x1160 ? tca_action_gd+0x990/0x990 ? sched_clock+0x5/0x10 ? find_held_lock+0x39/0x1d0 rtnetlink_rcv_msg+0x4da/0x990 ? validate_linkmsg+0x680/0x680 ? sched_clock_cpu+0x18/0x170 ? find_held_lock+0x39/0x1d0 netlink_rcv_skb+0x127/0x350 ? validate_linkmsg+0x680/0x680 ? netlink_ack+0x970/0x970 ? __kmalloc_node_track_caller+0x304/0x3a0 netlink_unicast+0x40f/0x5d0 ? netlink_attachskb+0x580/0x580 ? _copy_from_iter_full+0x187/0x760 ? import_iovec+0x90/0x390 netlink_sendmsg+0x67f/0xb50 ? netlink_unicast+0x5d0/0x5d0 ? copy_msghdr_from_user+0x206/0x340 ? netlink_unicast+0x5d0/0x5d0 sock_sendmsg+0xb3/0xf0 ___sys_sendmsg+0x60a/0x8b0 ? copy_msghdr_from_user+0x340/0x340 ? lock_downgrade+0x5e0/0x5e0 ? tty_write_lock+0x18/0x50 ? kvm_sched_clock_read+0x1a/0x30 ? sched_clock+0x5/0x10 ? sched_clock_cpu+0x18/0x170 ? find_held_lock+0x39/0x1d0 ? lock_downgrade+0x5e0/0x5e0 ? lock_acquire+0x10b/0x330 ? __audit_syscall_entry+0x316/0x690 ? current_kernel_time64+0x6b/0xd0 ? __fget_light+0x55/0x1f0 ? __sys_sendmsg+0xd2/0x170 __sys_sendmsg+0xd2/0x170 ? __ia32_sys_shutdown+0x70/0x70 ? syscall_trace_enter+0x57a/0xd60 ? rcu_read_lock_sched_held+0xdc/0x110 ? __bpf_trace_sys_enter+0x10/0x10 ? do_syscall_64+0x22/0x480 do_syscall_64+0xa5/0x480 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7fd646988ba0 RSP: 002b:00007fffc9fab3c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007fffc9fab4f0 RCX: 00007fd646988ba0 RDX: 0000000000000000 RSI: 00007fffc9fab440 RDI: 0000000000000003 RBP: 000000005b28c8b3 R08: 0000000000000002 R09: 0000000000000000 R10: 00007fffc9faae20 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fffc9fab504 R14: 0000000000000001 R15: 000000000066c100 Fixes: |
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| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| 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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.