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Eric W. Biederman f7cfd871ae exec: Transform exec_update_mutex into a rw_semaphore 
Recently syzbot reported[0] that there is a deadlock amongst the users
of exec_update_mutex.  The problematic lock ordering found by lockdep
was:

   perf_event_open  (exec_update_mutex -> ovl_i_mutex)
   chown            (ovl_i_mutex       -> sb_writes)
   sendfile         (sb_writes         -> p->lock)
     by reading from a proc file and writing to overlayfs
   proc_pid_syscall (p->lock           -> exec_update_mutex)

While looking at possible solutions it occured to me that all of the
users and possible users involved only wanted to state of the given
process to remain the same.  They are all readers.  The only writer is
exec.

There is no reason for readers to block on each other.  So fix
this deadlock by transforming exec_update_mutex into a rw_semaphore
named exec_update_lock that only exec takes for writing.

Cc: Jann Horn <jannh@google.com>
Cc: Vasiliy Kulikov <segoon@openwall.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Bernd Edlinger <bernd.edlinger@hotmail.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Christopher Yeoh <cyeoh@au1.ibm.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Sargun Dhillon <sargun@sargun.me>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Fixes: eea9673250 ("exec: Add exec_update_mutex to replace cred_guard_mutex")
[0] https://lkml.kernel.org/r/00000000000063640c05ade8e3de@google.com
Reported-by: syzbot+db9cdf3dd1f64252c6ef@syzkaller.appspotmail.com
Link: https://lkml.kernel.org/r/87ft4mbqen.fsf@x220.int.ebiederm.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
 		2020-12-10 13:13:32 -06:00
..
bpf bpf: Relax return code check for subprograms 2020-11-14 08:17:27 -08:00
cgroup kernel/: fix repeated words in comments 2020-10-16 11:11:19 -07:00
configs
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debug kdb: Fix pager search for multi-line strings 2020-10-01 14:44:08 +01:00
dma swiotlb: remove the tbl_dma_addr argument to swiotlb_tbl_map_single 2020-11-02 10:10:39 -05:00
entry entry: Fix the incorrect ordering of lockdep and RCU check 2020-11-04 18:06:14 +01:00
events exec: Transform exec_update_mutex into a rw_semaphore 2020-12-10 13:13:32 -06:00
gcov gcov: add support for GCC 10.1 2020-09-11 09:33:54 -07:00
irq A set of fixes for interrupt chip drivers: 2020-11-08 09:52:57 -08:00
kcsan kernel/: fix repeated words in comments 2020-10-16 11:11:19 -07:00
livepatch kernel/: fix repeated words in comments 2020-10-16 11:11:19 -07:00
locking rwsem: Implement down_read_interruptible 2020-12-09 17:08:42 +01:00
power PM: sleep: fix typo in kernel/power/process.c 2020-10-27 19:11:44 +01:00
printk Urgent printk fix for 5.10 2020-11-27 10:38:36 -08:00
rcu Merge branch 'urgent-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu 2020-11-17 10:31:56 -08:00
sched Yet two more places which invoke tracing from RCU disabled regions in the 2020-11-29 11:19:26 -08:00
time time: Prevent undefined behaviour in timespec64_to_ns() 2020-10-26 11:48:11 +01:00
trace Tracing fixes for 5.10-rc6 2020-12-01 15:30:18 -08:00
.gitignore
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Kconfig.freezer
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Kconfig.hz
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Kconfig.locks
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Kconfig.preempt
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Makefile Kbuild updates for v5.10 2020-10-22 13:13:57 -07:00
acct.c kernel: acct.c: fix some kernel-doc nits 2020-10-16 11:11:19 -07:00
async.c treewide: Remove uninitialized_var() usage 2020-07-16 12:35:15 -07:00
audit.c audit: Remove redundant null check 2020-08-26 09:10:39 -04:00
audit.h audit: change unnecessary globals into statics 2020-08-17 20:26:58 -04:00
audit_fsnotify.c fsnotify: create method handle_inode_event() in fsnotify_operations 2020-07-27 23:25:50 +02:00
audit_tree.c \n 2020-08-06 19:29:51 -07:00
audit_watch.c fsnotify: create method handle_inode_event() in fsnotify_operations 2020-07-27 23:25:50 +02:00
auditfilter.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
auditsc.c audit/stable-5.9 PR 20200803 2020-08-04 14:20:26 -07:00
backtracetest.c treewide: Replace DECLARE_TASKLET() with DECLARE_TASKLET_OLD() 2020-07-30 11:15:58 -07:00
bounds.c
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capability.c LSM: Signal to SafeSetID when setting group IDs 2020-10-13 09:17:34 -07:00
compat.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
configs.c
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context_tracking.c context_tracking: Ensure that the critical path cannot be instrumented 2020-06-11 15:14:36 +02:00
cpu.c The changes in this cycle are: 2020-06-03 13:06:42 -07:00
cpu_pm.c notifier: Fix broken error handling pattern 2020-09-01 09:58:03 +02:00
crash_core.c kdump: append kernel build-id string to VMCOREINFO 2020-08-12 10:58:01 -07:00
crash_dump.c crash_dump: Remove no longer used saved_max_pfn 2020-04-15 11:21:54 +02:00
cred.c exec: Teach prepare_exec_creds how exec treats uids & gids 2020-05-20 14:44:21 -05:00
delayacct.c
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dma.c
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elfcore.c
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exec_domain.c
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exit.c don't dump the threads that had been already exiting when zapped. 2020-10-28 16:39:49 -04:00
extable.c
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fail_function.c fail_function: Remove a redundant mutex unlock 2020-11-19 11:58:16 -08:00
fork.c exec: Transform exec_update_mutex into a rw_semaphore 2020-12-10 13:13:32 -06:00
freezer.c
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futex.c futex: Don't enable IRQs unconditionally in put_pi_state() 2020-11-09 14:30:30 +01:00
gen_kheaders.sh kbuild: add variables for compression tools 2020-06-06 23:42:01 +09:00
groups.c LSM: Signal to SafeSetID when setting group IDs 2020-10-13 09:17:34 -07:00
hung_task.c kernel/hung_task.c: make type annotations consistent 2020-11-02 12:14:19 -08:00
iomem.c
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irq_work.c irq_work, smp: Allow irq_work on call_single_queue 2020-05-28 10:54:15 +02:00
jump_label.c kernel/: fix repeated words in comments 2020-10-16 11:11:19 -07:00
kallsyms.c treewide: Convert macro and uses of __section(foo) to __section("foo") 2020-10-25 14:51:49 -07:00
kcmp.c exec: Transform exec_update_mutex into a rw_semaphore 2020-12-10 13:13:32 -06:00
kcov.c kcov: make some symbols static 2020-08-12 10:58:02 -07:00
kexec.c LSM: Introduce kernel_post_load_data() hook 2020-10-05 13:37:03 +02:00
kexec_core.c kernel/: fix repeated words in comments 2020-10-16 11:11:19 -07:00
kexec_elf.c
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kexec_file.c kernel/resource: move and rename IORESOURCE_MEM_DRIVER_MANAGED 2020-10-16 11:11:18 -07:00
kexec_internal.h
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kheaders.c
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kmod.c kmod: remove redundant "be an" in the comment 2020-08-12 10:58:01 -07:00
kprobes.c kprobes: Tell lockdep about kprobe nesting 2020-11-04 09:46:06 -05:00
ksysfs.c
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kthread.c kthread_worker: prevent queuing delayed work from timer_fn when it is being canceled 2020-11-02 12:14:19 -08:00
latencytop.c sysctl: pass kernel pointers to ->proc_handler 2020-04-27 02:07:40 -04:00
module-internal.h
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module.c Modules updates for v5.10 2020-10-22 13:08:57 -07:00
module_signature.c
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module_signing.c
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notifier.c notifier: Fix broken error handling pattern 2020-09-01 09:58:03 +02:00
nsproxy.c nsproxy: support CLONE_NEWTIME with setns() 2020-07-08 11:14:22 +02:00
padata.c padata: fix possible padata_works_lock deadlock 2020-09-04 17:51:55 +10:00
panic.c panic: don't dump stack twice on warn 2020-11-14 11:26:04 -08:00
params.c params: Replace zero-length array with flexible-array member 2020-10-29 17:22:59 -05:00
pid.c exec: Transform exec_update_mutex into a rw_semaphore 2020-12-10 13:13:32 -06:00
pid_namespace.c kernel/: fix repeated words in comments 2020-10-16 11:11:19 -07:00
profile.c
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ptrace.c ptrace: Set PF_SUPERPRIV when checking capability 2020-11-17 12:53:22 -08:00
range.c kernel.h: split out min()/max() et al. helpers 2020-10-16 11:11:19 -07:00
reboot.c reboot: fix overflow parsing reboot cpu number 2020-11-14 11:26:03 -08:00
regset.c regset: kill ->get() 2020-07-27 14:31:12 -04:00
relay.c kernel/relay.c: drop unneeded initialization 2020-10-16 11:11:22 -07:00
resource.c kernel/resource: make iomem_resource implicit in release_mem_region_adjustable() 2020-10-16 11:11:18 -07:00
rseq.c
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scftorture.c scftorture: Add cond_resched() to test loop 2020-08-24 18:38:38 -07:00
scs.c mm: memcontrol: account kernel stack per node 2020-08-07 11:33:25 -07:00
seccomp.c seccomp: Set PF_SUPERPRIV when checking capability 2020-11-17 12:53:22 -08:00
signal.c ptrace: fix task_join_group_stop() for the case when current is traced 2020-11-02 12:14:19 -08:00
smp.c Merge tag 'core-rcu-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2020-10-18 14:34:50 -07:00
smpboot.c
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smpboot.h
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softirq.c softirq: Add debug check to __raise_softirq_irqoff() 2020-09-16 15:18:56 +02:00
stackleak.c stackleak: let stack_erasing_sysctl take a kernel pointer buffer 2020-09-19 13:13:39 -07:00
stacktrace.c stacktrace: Remove reliable argument from arch_stack_walk() callback 2020-09-18 14:24:16 +01:00
static_call.c static_call: Fix return type of static_call_init 2020-10-02 21:18:25 +02:00
stop_machine.c stop_machine, rcu: Mark functions as notrace 2020-10-26 12:12:27 +01:00
sys.c kernel/sys.c: fix prototype of prctl_get_tid_address() 2020-10-25 11:44:16 -07:00
sys_ni.c mm/madvise: introduce process_madvise() syscall: an external memory hinting API 2020-10-18 09:27:10 -07:00
sysctl-test.c
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sysctl.c mm: allow a controlled amount of unfairness in the page lock 2020-09-17 10:26:41 -07:00
task_work.c task_work: cleanup notification modes 2020-10-17 15:05:30 -06:00
taskstats.c taskstats: move specifying netlink policy back to ops 2020-10-02 19:11:12 -07:00
test_kprobes.c
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torture.c torture: Dump ftrace at shutdown only if requested 2020-06-29 12:01:45 -07:00
tracepoint.c tracepoint: Replace zero-length array with flexible-array member 2020-10-29 17:22:59 -05:00
tsacct.c
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ucount.c
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uid16.c
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uid16.h
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umh.c usermodehelper: reset umask to default before executing user process 2020-10-06 10:31:52 -07:00
up.c
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user-return-notifier.c
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user.c user.c: make uidhash_table static 2020-06-04 19:06:24 -07:00
user_namespace.c kernel/: fix repeated words in comments 2020-10-16 11:11:19 -07:00
usermode_driver.c umd: Stop using split_argv 2020-07-07 11:58:59 -05:00
utsname.c nsproxy: add struct nsset 2020-05-09 13:57:12 +02:00
utsname_sysctl.c sysctl: pass kernel pointers to ->proc_handler 2020-04-27 02:07:40 -04:00
watch_queue.c watch_queue: Limit the number of watches a user can hold 2020-08-17 09:39:18 -07:00
watchdog.c kernel/watchdog: fix watchdog_allowed_mask not used warning 2020-11-14 11:26:03 -08:00
watchdog_hld.c
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workqueue.c workqueue: fix a kernel-doc warning 2020-10-16 07:28:20 +02:00
workqueue_internal.h
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