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linux/kernel
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Rusty Russell 6fb5717048 UPSTREAM: modules: fix longstanding /proc/kallsyms vs module insertion race. 
commit 8244062ef1 upstream.

For CONFIG_KALLSYMS, we keep two symbol tables and two string tables.
There's one full copy, marked SHF_ALLOC and laid out at the end of the
module's init section.  There's also a cut-down version that only
contains core symbols and strings, and lives in the module's core
section.

After module init (and before we free the module memory), we switch
the mod->symtab, mod->num_symtab and mod->strtab to point to the core
versions.  We do this under the module_mutex.

However, kallsyms doesn't take the module_mutex: it uses
preempt_disable() and rcu tricks to walk through the modules, because
it's used in the oops path.  It's also used in /proc/kallsyms.
There's nothing atomic about the change of these variables, so we can
get the old (larger!) num_symtab and the new symtab pointer; in fact
this is what I saw when trying to reproduce.

By grouping these variables together, we can use a
carefully-dereferenced pointer to ensure we always get one or the
other (the free of the module init section is already done in an RCU
callback, so that's safe).  We allocate the init one at the end of the
module init section, and keep the core one inside the struct module
itself (it could also have been allocated at the end of the module
core, but that's probably overkill).

Reported-by: Weilong Chen <chenweilong@huawei.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=111541
Cc: stable@kernel.org
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
[AmitP: LTS backport is reverted earlier in lsk-android commit
        3f237b5bfda5 ("Revert "modules: fix longstanding /proc/kallsyms vs module insertion race."),
        Re-apply the upstream version instead along with related
        set of dependent patches.]
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
2017-08-11 19:31:04 +05:30
..
bpf Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android 2017-07-22 12:02:06 +08:00
configs kconfig: tinyconfig: provide whole choice blocks to avoid warnings 2016-09-24 10:07:42 +02:00
debug UPSTREAM: module: use a structure to encapsulate layout. 2017-08-11 19:31:04 +05:30
events Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android 2017-07-28 12:01:36 +08:00
gcov UPSTREAM: gcov: use within_module() helper. 2017-08-11 19:31:04 +05:30
irq genirq: Release resources in __setup_irq() error path 2017-06-26 07:13:10 +02:00
livepatch livepatch: x86: fix relocation computation with kASLR 2015-11-11 17:36:04 +01:00
locking UPSTREAM: locking: avoid passing around 'thread_info' in mutex debugging code 2017-08-11 19:31:04 +05:30
power UPSTREAM: PM / sleep: make PM notifiers called symmetrically 2017-05-01 15:02:13 +05:30
printk UPSTREAM: printk: when dumping regs, show the stack, not thread_info 2017-08-11 19:31:04 +05:30
rcu Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android 2016-12-12 22:17:37 +08:00
sched UPSTREAM: sched/core: Allow putting thread_info into task_struct 2017-08-11 19:31:04 +05:30
time UPSTREAM: cpufreq: schedutil: Avoid reducing frequency of busy CPUs prematurely 2017-08-11 19:31:04 +05:30
trace Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android 2017-07-28 12:01:36 +08:00
.gitignore certs: add .gitignore to stop git nagging about x509_certificate_list 2015-10-21 15:18:35 +01:00
acct.c
async.c
audit_fsnotify.c
audit_tree.c audit: audit_tree_match can be boolean 2015-11-04 08:23:51 -05:00
audit_watch.c audit: fix exe_file access in audit_exe_compare 2016-09-24 10:07:36 +02:00
audit.c BACKPORT: audit: consistently record PIDs with task_tgid_nr() 2016-10-12 17:34:22 +05:30
audit.h audit: audit_tree_match can be boolean 2015-11-04 08:23:51 -05:00
auditfilter.c audit: fix comment block whitespace 2015-11-04 08:23:51 -05:00
auditsc.c BACKPORT: audit: consistently record PIDs with task_tgid_nr() 2016-10-12 17:34:22 +05:30
backtracetest.c
bounds.c
capability.c exec: Ensure mm->user_ns contains the execed files 2017-01-06 11:16:14 +01:00
cgroup_freezer.c cgroup: fix handling of multi-destination migration from subtree_control enabling 2015-12-03 10:18:21 -05:00
cgroup_pids.c cgroup_pids: don't account for the root cgroup 2015-12-03 10:18:21 -05:00
cgroup.c Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android 2017-04-23 12:02:14 +08:00
compat.c
configs.c
context_tracking.c context_tracking: avoid irq_save/irq_restore on guest entry and exit 2015-11-10 12:06:23 +01:00
cpu_pm.c
cpu.c Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android 2017-01-13 12:01:52 +08:00
cpuset.c Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android 2017-07-11 16:22:22 +08:00
crash_dump.c
cred.c cred: Reject inodes with invalid ids in set_create_file_as() 2016-09-15 08:27:49 +02:00
delayacct.c
dma.c
elfcore.c
exec_domain.c
exit.c FIXUP: sched/tune: fix accounting for runnable tasks 2016-09-14 14:59:32 +05:30
extable.c kernel/extable.c: mark core_kernel_text notrace 2017-07-21 07:44:56 +02:00
fork.c UPSTREAM: Clarify naming of thread info/stack allocators 2017-08-11 19:31:04 +05:30
freezer.c
futex_compat.c ptrace: use fsuid, fsgid, effective creds for fs access checks 2016-02-25 12:01:16 -08:00
futex.c Merge tag 'v4.4.56' into linux-linaro-lsk-v4.4 2017-03-23 12:00:54 +08:00
groups.c
hung_task.c
irq_work.c treewide: Remove old email address 2015-11-23 09:44:58 +01:00
jump_label.c jump_labels: API for flushing deferred jump label updates 2017-01-19 20:17:19 +01:00
kallsyms.c
kcmp.c ptrace: use fsuid, fsgid, effective creds for fs access checks 2016-02-25 12:01:16 -08:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kexec_core.c kexec: use file name as the output message prefix 2015-11-06 17:50:42 -08:00
kexec_file.c kexec: fix double-free when failing to relocate the purgatory 2016-09-24 10:07:36 +02:00
kexec_internal.h kexec: split kexec_file syscall code to kexec_file.c 2015-09-10 13:29:01 -07:00
kexec.c kexec: use file name as the output message prefix 2015-11-06 17:50:42 -08:00
kmod.c kmod: don't run async usermode helper as a child of kworker thread 2015-10-23 17:55:10 +09:00
kprobes.c tracing/kprobes: Enforce kprobes teardown after testing 2017-05-25 14:30:17 +02:00
ksysfs.c kexec: split kexec_load syscall from kexec core code 2015-09-10 13:29:01 -07:00
kthread.c UPSTREAM: kthread: Pin the stack via try_get_task_stack()/put_task_stack() in to_live_kthread() function 2017-08-11 19:31:04 +05:30
latencytop.c
Makefile sys_membarrier(): system-wide memory barrier (generic, x86) 2015-09-11 15:21:34 -07:00
membarrier.c Fix: Disable sys_membarrier when nohz_full is enabled 2017-03-12 06:37:26 +01:00
memremap.c mm: fix devm_memremap_pages crash, use mem_hotplug_{begin, done} 2017-01-19 20:17:18 +01:00
module_signing.c KEYS: Merge the type-specific data with the payload data 2015-10-21 15:18:36 +01:00
module-internal.h
module.c UPSTREAM: modules: fix longstanding /proc/kallsyms vs module insertion race. 2017-08-11 19:31:04 +05:30
notifier.c
nsproxy.c
padata.c padata: free correct variable 2017-05-20 14:27:02 +02:00
panic.c kernel/panic.c: add missing \n 2017-07-05 14:37:19 +02:00
params.c Nothing exciting, minor tweaks and cleanups. 2015-11-09 15:53:39 -08:00
pid_namespace.c pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes 2017-05-25 14:30:11 +02:00
pid.c pidns: fix NULL dereference in __task_pid_nr_ns() 2015-11-24 12:03:55 -08:00
profile.c mm: rename alloc_pages_exact_node() to __alloc_pages_node() 2015-09-08 15:35:28 -07:00
ptrace.c ptrace: Properly initialize ptracer_cred on fork 2017-06-14 13:16:20 +02:00
range.c
reboot.c kexec: split kexec_load syscall from kexec core code 2015-09-10 13:29:01 -07:00
relay.c
resource.c /proc/iomem: only expose physical resource addresses to privileged users 2017-08-06 19:19:42 -07:00
seccomp.c seccomp: always propagate NO_NEW_PRIVS on tsync 2016-03-03 15:07:25 -08:00
signal.c signal: Only reschedule timers on signals timers have sent 2017-06-29 12:48:51 +02:00
smp.c mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd 2015-11-06 17:50:42 -08:00
smpboot.c stop_machine: Kill smp_hotplug_thread->pre_unpark, introduce stop_machine_unpark() 2015-10-20 10:23:55 +02:00
smpboot.h
softirq.c
stacktrace.c
stop_machine.c kernel: remove stop_machine() Kconfig dependency 2015-12-12 10:15:34 -08:00
sys_ni.c mm: mlock: add new mlock system call 2015-11-05 19:34:48 -08:00
sys.c BACKPORT: timer: convert timer_slack_ns from unsigned long to u64 2016-07-11 12:43:04 +05:30
sysctl_binary.c fs/coredump: prevent fsuid=0 dumps into user-controlled directories 2016-04-12 09:08:58 -07:00
sysctl.c Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android 2017-07-18 14:31:54 +08:00
task_work.c task_work: remove fifo ordering guarantee 2015-09-05 13:46:58 -07:00
taskstats.c
test_kprobes.c
torture.c torture: Consolidate cond_resched_rcu_qs() into stutter_wait() 2015-10-06 11:25:01 -07:00
tracepoint.c tracepoint: Give priority to probes of tracepoints 2015-10-25 21:33:54 -04:00
tsacct.c
uid16.c
up.c
user_namespace.c capabilities: ambient capabilities 2015-09-04 16:54:41 -07:00
user-return-notifier.c
user.c
utsname_sysctl.c
utsname.c
watchdog.c Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android 2017-01-09 12:01:35 +08:00
workqueue_internal.h
workqueue.c workqueue: fix rebind bound workers warning 2016-05-18 17:06:50 -07:00