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Nikolay Aleksandrov 6555d5440b ip6mr: fix stale iterator [ Upstream commit `4adfa79fc2` ] When we dump the ip6mr mfc entries via proc, we initialize an iterator with the table to dump but we don't clear the cache pointer which might be initialized from a prior read on the same descriptor that ended. This can result in lock imbalance (an unnecessary unlock) leading to other crashes and hangs. Clear the cache pointer like ipmr does to fix the issue. Thanks for the reliable reproducer. Here's syzbot's trace: WARNING: bad unlock balance detected! 4.15.0-rc3+ #128 Not tainted syzkaller971460/3195 is trying to release lock (mrt_lock) at: [<000000006898068d>] ipmr_mfc_seq_stop+0xe1/0x130 net/ipv6/ip6mr.c:553 but there are no more locks to release! other info that might help us debug this: 1 lock held by syzkaller971460/3195: #0: (&p->lock){+.+.}, at: [<00000000744a6565>] seq_read+0xd5/0x13d0 fs/seq_file.c:165 stack backtrace: CPU: 1 PID: 3195 Comm: syzkaller971460 Not tainted 4.15.0-rc3+ #128 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:53 print_unlock_imbalance_bug+0x12f/0x140 kernel/locking/lockdep.c:3561 __lock_release kernel/locking/lockdep.c:3775 [inline] lock_release+0x5f9/0xda0 kernel/locking/lockdep.c:4023 __raw_read_unlock include/linux/rwlock_api_smp.h:225 [inline] _raw_read_unlock+0x1a/0x30 kernel/locking/spinlock.c:255 ipmr_mfc_seq_stop+0xe1/0x130 net/ipv6/ip6mr.c:553 traverse+0x3bc/0xa00 fs/seq_file.c:135 seq_read+0x96a/0x13d0 fs/seq_file.c:189 proc_reg_read+0xef/0x170 fs/proc/inode.c:217 do_loop_readv_writev fs/read_write.c:673 [inline] do_iter_read+0x3db/0x5b0 fs/read_write.c:897 compat_readv+0x1bf/0x270 fs/read_write.c:1140 do_compat_preadv64+0xdc/0x100 fs/read_write.c:1189 C_SYSC_preadv fs/read_write.c:1209 [inline] compat_SyS_preadv+0x3b/0x50 fs/read_write.c:1203 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline] do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389 entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:125 RIP: 0023:0xf7f73c79 RSP: 002b:00000000e574a15c EFLAGS: 00000292 ORIG_RAX: 000000000000014d RAX: ffffffffffffffda RBX: 000000000000000f RCX: 0000000020a3afb0 RDX: 0000000000000001 RSI: 0000000000000067 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 BUG: sleeping function called from invalid context at lib/usercopy.c:25 in_atomic(): 1, irqs_disabled(): 0, pid: 3195, name: syzkaller971460 INFO: lockdep is turned off. CPU: 1 PID: 3195 Comm: syzkaller971460 Not tainted 4.15.0-rc3+ #128 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:53 ___might_sleep+0x2b2/0x470 kernel/sched/core.c:6060 __might_sleep+0x95/0x190 kernel/sched/core.c:6013 __might_fault+0xab/0x1d0 mm/memory.c:4525 _copy_to_user+0x2c/0xc0 lib/usercopy.c:25 copy_to_user include/linux/uaccess.h:155 [inline] seq_read+0xcb4/0x13d0 fs/seq_file.c:279 proc_reg_read+0xef/0x170 fs/proc/inode.c:217 do_loop_readv_writev fs/read_write.c:673 [inline] do_iter_read+0x3db/0x5b0 fs/read_write.c:897 compat_readv+0x1bf/0x270 fs/read_write.c:1140 do_compat_preadv64+0xdc/0x100 fs/read_write.c:1189 C_SYSC_preadv fs/read_write.c:1209 [inline] compat_SyS_preadv+0x3b/0x50 fs/read_write.c:1203 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline] do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389 entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:125 RIP: 0023:0xf7f73c79 RSP: 002b:00000000e574a15c EFLAGS: 00000292 ORIG_RAX: 000000000000014d RAX: ffffffffffffffda RBX: 000000000000000f RCX: 0000000020a3afb0 RDX: 0000000000000001 RSI: 0000000000000067 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 WARNING: CPU: 1 PID: 3195 at lib/usercopy.c:26 _copy_to_user+0xb5/0xc0 lib/usercopy.c:26 Reported-by: syzbot <bot+eceb3204562c41a438fa1f2335e0fe4f6886d669@syzkaller.appspotmail.com> Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		History 2018-02-12 07:07:18 +01:00
arch	KVM/SVM: Allow direct access to MSR_IA32_SPEC_CTRL	2018-02-07 11:14:14 -08:00
block	block: drain queue before waiting for q_usage_counter becoming zero	2018-01-05 09:09:48 -07:00
certs	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
crypto	crypto: af_alg - whitelist mask and type	2018-02-03 17:58:33 +01:00
Documentation	x86/paravirt: Remove 'noreplace-paravirt' cmdline option	2018-02-07 11:14:13 -08:00
drivers	fpga: region: release of_parse_phandle nodes after use	2018-02-07 11:14:15 -08:00
firmware	kbuild: remove all dummy assignments to obj-	2017-11-18 11:46:06 +09:00
fs	orangefs: fix deadlock; do not write i_size in read_iter	2018-01-25 17:26:24 -08:00
include	x86/retpoline: Avoid retpolines for built-in __init functions	2018-02-07 11:14:13 -08:00
init	Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2018-01-12 10:23:59 -08:00
ipc	Rename superblock flags (MS_xyz -> SB_xyz)	2017-11-27 13:05:09 -08:00
kernel	module/retpoline: Warn about missing retpoline in module	2018-02-07 11:14:06 -08:00
lib	test_firmware: fix missing unlock on error in config_num_requests_store()	2018-02-03 17:58:43 +01:00
mm	mm, page_vma_mapped: Introduce pfn_in_hpage()	2018-01-22 12:15:57 -08:00
net	ip6mr: fix stale iterator	2018-02-12 07:07:18 +01:00
samples	Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf	2017-12-03 13:08:30 -05:00
scripts	module/retpoline: Warn about missing retpoline in module	2018-02-07 11:14:06 -08:00
security	ima/policy: fix parsing of fsuuid	2018-02-03 17:58:35 +01:00
sound	ASoC: pcm512x: add missing MODULE_DESCRIPTION/AUTHOR/LICENSE	2018-02-07 11:14:09 -08:00
tools	objtool: Warn on stripped section symbol	2018-02-07 11:14:09 -08:00
usr	initramfs: fix initramfs rebuilds w/ compression after disabling	2017-11-03 07:39:19 -07:00
virt	KVM/ARM Fixes for v4.15, Round 3 (v2)	2018-01-17 14:59:27 +01:00
.cocciconfig	scripts: add Linux .cocciconfig for coccinelle	2016-07-22 12:13:39 +02:00
.get_maintainer.ignore	Add hch to .get_maintainer.ignore	2015-08-21 14:30:10 -07:00
.gitattributes	.gitattributes: set git diff driver for C source code files	2016-10-07 18:46:30 -07:00
.gitignore	Kbuild misc updates for v4.15	2017-11-17 17:51:33 -08:00
.mailmap	mailmap: update Mark Yao's email address	2018-01-04 16:45:09 -08:00
COPYING	[PATCH] update FSF address in COPYING	2005-09-10 10:06:29 -07:00
CREDITS	MAINTAINERS: update TPM driver infrastructure changes	2017-11-09 17:58:40 -08:00
Kbuild	Kbuild updates for v4.15	2017-11-17 17:45:29 -08:00
Kconfig	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
MAINTAINERS	Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2018-01-28 12:19:23 -08:00
Makefile	Linux 4.15.2	2018-02-07 11:14:15 -08:00
README	README: add a new README file, pointing to the Documentation/	2016-10-24 08:12:35 -02:00

README

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

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.