linux.git/kernel/module.c, branch v3.10.103

module: Invalidate signatures on force-loaded modules

2016-08-27T09:40:39+00:00

commit bca014caaa6130e57f69b5bf527967aa8ee70fdd upstream.

Signing a module should only make it trusted by the specific kernel it
was built for, not anything else.  Loading a signed module meant for a
kernel with a different ABI could have interesting effects.
Therefore, treat all signatures as invalid when a module is
force-loaded.

Signed-off-by: Ben Hutchings 
Signed-off-by: Rusty Russell 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Willy Tarreau

modules: fix longstanding /proc/kallsyms vs module insertion race.

2016-03-16T15:41:37+00:00

commit 8244062ef1e54502ef55f54cced659913f244c3e 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).

[ Rebased for 4.4-stable and older, because the following changes aren't
  in the older trees:
  - e0224418516b4d8a6c2160574bac18447c354ef0: adds arg to is_core_symbol
  - 7523e4dc5057e157212b4741abd6256e03404cf1: module_init/module_core/init_size/core_size
    become init_layout.base/core_layout.base/init_layout.size/core_layout.size.

  Original commit: 8244062ef1e54502ef55f54cced659913f244c3e
]

Reported-by: Weilong Chen 
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=111541
Signed-off-by: Rusty Russell 
Signed-off-by: Greg Kroah-Hartman

module: wrapper for symbol name.

2016-02-25T19:57:50+00:00

commit 2e7bac536106236104e9e339531ff0fcdb7b8147 upstream.

This trivial wrapper adds clarity and makes the following patch
smaller.

Signed-off-by: Rusty Russell 
Signed-off-by: Greg Kroah-Hartman

module: Fix locking in symbol_put_addr()

2015-11-09T18:12:59+00:00

commit 275d7d44d802ef271a42dc87ac091a495ba72fc5 upstream.

Poma (on the way to another bug) reported an assertion triggering:

  [] module_assert_mutex_or_preempt+0x49/0x90
  [] __module_address+0x32/0x150
  [] __module_text_address+0x16/0x70
  [] symbol_put_addr+0x29/0x40
  [] dvb_frontend_detach+0x7d/0x90 [dvb_core]

Laura Abbott  produced a patch which lead us to
inspect symbol_put_addr(). This function has a comment claiming it
doesn't need to disable preemption around the module lookup
because it holds a reference to the module it wants to find, which
therefore cannot go away.

This is wrong (and a false optimization too, preempt_disable() is really
rather cheap, and I doubt any of this is on uber critical paths,
otherwise it would've retained a pointer to the actual module anyway and
avoided the second lookup).

While its true that the module cannot go away while we hold a reference
on it, the data structure we do the lookup in very much _CAN_ change
while we do the lookup. Therefore fix the comment and add the
required preempt_disable().

Reported-by: poma 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Rusty Russell 
Fixes: a6e6abd575fc ("module: remove module_text_address()")
Signed-off-by: Greg Kroah-Hartman

modules, lock around setting of MODULE_STATE_UNFORMED

2014-11-14T16:47:55+00:00

commit d3051b489aa81ca9ba62af366149ef42b8dae97c upstream.

A panic was seen in the following sitation.

There are two threads running on the system. The first thread is a system
monitoring thread that is reading /proc/modules. The second thread is
loading and unloading a module (in this example I'm using my simple
dummy-module.ko).  Note, in the "real world" this occurred with the qlogic
driver module.

When doing this, the following panic occurred:

 ------------[ cut here ]------------
 kernel BUG at kernel/module.c:3739!
 invalid opcode: 0000 [#1] SMP
 Modules linked in: binfmt_misc sg nfsv3 rpcsec_gss_krb5 nfsv4 dns_resolver nfs fscache intel_powerclamp coretemp kvm_intel kvm crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel lrw igb gf128mul glue_helper iTCO_wdt iTCO_vendor_support ablk_helper ptp sb_edac cryptd pps_core edac_core shpchp i2c_i801 pcspkr wmi lpc_ich ioatdma mfd_core dca ipmi_si nfsd ipmi_msghandler auth_rpcgss nfs_acl lockd sunrpc xfs libcrc32c sr_mod cdrom sd_mod crc_t10dif crct10dif_common mgag200 syscopyarea sysfillrect sysimgblt i2c_algo_bit drm_kms_helper ttm isci drm libsas ahci libahci scsi_transport_sas libata i2c_core dm_mirror dm_region_hash dm_log dm_mod [last unloaded: dummy_module]
 CPU: 37 PID: 186343 Comm: cat Tainted: GF          O--------------   3.10.0+ #7
 Hardware name: Intel Corporation S2600CP/S2600CP, BIOS RMLSDP.86I.00.29.D696.1311111329 11/11/2013
 task: ffff8807fd2d8000 ti: ffff88080fa7c000 task.ti: ffff88080fa7c000
 RIP: 0010:[]  [] module_flags+0xb5/0xc0
 RSP: 0018:ffff88080fa7fe18  EFLAGS: 00010246
 RAX: 0000000000000003 RBX: ffffffffa03b5200 RCX: 0000000000000000
 RDX: 0000000000001000 RSI: ffff88080fa7fe38 RDI: ffffffffa03b5000
 RBP: ffff88080fa7fe28 R08: 0000000000000010 R09: 0000000000000000
 R10: 0000000000000000 R11: 000000000000000f R12: ffffffffa03b5000
 R13: ffffffffa03b5008 R14: ffffffffa03b5200 R15: ffffffffa03b5000
 FS:  00007f6ae57ef740(0000) GS:ffff88101e7a0000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000404f70 CR3: 0000000ffed48000 CR4: 00000000001407e0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
 Stack:
  ffffffffa03b5200 ffff8810101e4800 ffff88080fa7fe70 ffffffff810d666c
  ffff88081e807300 000000002e0f2fbf 0000000000000000 ffff88100f257b00
  ffffffffa03b5008 ffff88080fa7ff48 ffff8810101e4800 ffff88080fa7fee0
 Call Trace:
  [] m_show+0x19c/0x1e0
  [] seq_read+0x16e/0x3b0
  [] proc_reg_read+0x3d/0x80
  [] vfs_read+0x9c/0x170
  [] SyS_read+0x58/0xb0
  [] system_call_fastpath+0x16/0x1b
 Code: 48 63 c2 83 c2 01 c6 04 03 29 48 63 d2 eb d9 0f 1f 80 00 00 00 00 48 63 d2 c6 04 13 2d 41 8b 0c 24 8d 50 02 83 f9 01 75 b2 eb cb <0f> 0b 66 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41
 RIP  [] module_flags+0xb5/0xc0
  RSP 

    Consider the two processes running on the system.

    CPU 0 (/proc/modules reader)
    CPU 1 (loading/unloading module)

    CPU 0 opens /proc/modules, and starts displaying data for each module by
    traversing the modules list via fs/seq_file.c:seq_open() and
    fs/seq_file.c:seq_read().  For each module in the modules list, seq_read
    does

            op->start()  <-- this is a pointer to m_start()
            op->show()   <- this is a pointer to m_show()
            op->stop()   <-- this is a pointer to m_stop()

    The m_start(), m_show(), and m_stop() module functions are defined in
    kernel/module.c. The m_start() and m_stop() functions acquire and release
    the module_mutex respectively.

    ie) When reading /proc/modules, the module_mutex is acquired and released
    for each module.

    m_show() is called with the module_mutex held.  It accesses the module
    struct data and attempts to write out module data.  It is in this code
    path that the above BUG_ON() warning is encountered, specifically m_show()
    calls

    static char *module_flags(struct module *mod, char *buf)
    {
            int bx = 0;

            BUG_ON(mod->state == MODULE_STATE_UNFORMED);
    ...

    The other thread, CPU 1, in unloading the module calls the syscall
    delete_module() defined in kernel/module.c.  The module_mutex is acquired
    for a short time, and then released.  free_module() is called without the
    module_mutex.  free_module() then sets mod->state = MODULE_STATE_UNFORMED,
    also without the module_mutex.  Some additional code is called and then the
    module_mutex is reacquired to remove the module from the modules list:

        /* Now we can delete it from the lists */
        mutex_lock(&module_mutex);
        stop_machine(__unlink_module, mod, NULL);
        mutex_unlock(&module_mutex);

This is the sequence of events that leads to the panic.

CPU 1 is removing dummy_module via delete_module().  It acquires the
module_mutex, and then releases it.  CPU 1 has NOT set dummy_module->state to
MODULE_STATE_UNFORMED yet.

CPU 0, which is reading the /proc/modules, acquires the module_mutex and
acquires a pointer to the dummy_module which is still in the modules list.
CPU 0 calls m_show for dummy_module.  The check in m_show() for
MODULE_STATE_UNFORMED passed for dummy_module even though it is being
torn down.

Meanwhile CPU 1, which has been continuing to remove dummy_module without
holding the module_mutex, now calls free_module() and sets
dummy_module->state to MODULE_STATE_UNFORMED.

CPU 0 now calls module_flags() with dummy_module and ...

static char *module_flags(struct module *mod, char *buf)
{
        int bx = 0;

        BUG_ON(mod->state == MODULE_STATE_UNFORMED);

and BOOM.

Acquire and release the module_mutex lock around the setting of
MODULE_STATE_UNFORMED in the teardown path, which should resolve the
problem.

Testing: In the unpatched kernel I can panic the system within 1 minute by
doing

while (true) do insmod dummy_module.ko; rmmod dummy_module.ko; done

and

while (true) do cat /proc/modules; done

in separate terminals.

In the patched kernel I was able to run just over one hour without seeing
any issues.  I also verified the output of panic via sysrq-c and the output
of /proc/modules looks correct for all three states for the dummy_module.

        dummy_module 12661 0 - Unloading 0xffffffffa03a5000 (OE-)
        dummy_module 12661 0 - Live 0xffffffffa03bb000 (OE)
        dummy_module 14015 1 - Loading 0xffffffffa03a5000 (OE+)

Signed-off-by: Prarit Bhargava 
Reviewed-by: Oleg Nesterov 
Signed-off-by: Rusty Russell 
Signed-off-by: Greg Kroah-Hartman

ftrace/module: Hardcode ftrace_module_init() call into load_module()

2014-06-07T20:25:28+00:00

commit a949ae560a511fe4e3adf48fa44fefded93e5c2b upstream.

A race exists between module loading and enabling of function tracer.

	CPU 1				CPU 2
	-----				-----
  load_module()
   module->state = MODULE_STATE_COMING

				register_ftrace_function()
				 mutex_lock(&ftrace_lock);
				 ftrace_startup()
				  update_ftrace_function();
				   ftrace_arch_code_modify_prepare()
				    set_all_module_text_rw();
				   
				    ftrace_arch_code_modify_post_process()
				     set_all_module_text_ro();

				[ here all module text is set to RO,
				  including the module that is
				  loading!! ]

   blocking_notifier_call_chain(MODULE_STATE_COMING);
    ftrace_init_module()

     [ tries to modify code, but it's RO, and fails!
       ftrace_bug() is called]

When this race happens, ftrace_bug() will produces a nasty warning and
all of the function tracing features will be disabled until reboot.

The simple solution is to treate module load the same way the core
kernel is treated at boot. To hardcode the ftrace function modification
of converting calls to mcount into nops. This is done in init/main.c
there's no reason it could not be done in load_module(). This gives
a better control of the changes and doesn't tie the state of the
module to its notifiers as much. Ftrace is special, it needs to be
treated as such.

The reason this would work, is that the ftrace_module_init() would be
called while the module is in MODULE_STATE_UNFORMED, which is ignored
by the set_all_module_text_ro() call.

Link: http://lkml.kernel.org/r/1395637826-3312-1-git-send-email-indou.takao@jp.fujitsu.com

Reported-by: Takao Indoh 
Acked-by: Rusty Russell 
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

module: do percpu allocation after uniqueness check. No, really!

2013-07-13T18:42:26+00:00

commit 8d8022e8aba85192e937f1f0f7450e256d66ae5c upstream.

v3.8-rc1-5-g1fb9341 was supposed to stop parallel kvm loads exhausting
percpu memory on large machines:

    Now we have a new state MODULE_STATE_UNFORMED, we can insert the
    module into the list (and thus guarantee its uniqueness) before we
    allocate the per-cpu region.

In my defence, it didn't actually say the patch did this.  Just that
we "can".

This patch actually *does* it.

Signed-off-by: Rusty Russell 
Tested-by: Jim Hull 
Signed-off-by: Greg Kroah-Hartman

kmemleak: No need for scanning specific module sections

2013-05-17T08:53:36+00:00

As kmemleak now scans all module sections that are allocated, writable
and non executable, there's no need to scan individual sections that
might reference data.

Signed-off-by: Steven Rostedt 
Signed-off-by: Catalin Marinas 
Acked-by: Rusty Russell

kmemleak: Scan all allocated, writeable and not executable module sections

2013-05-17T08:53:07+00:00

Instead of just picking data sections by name (names that start
with .data, .bss or .ref.data), use the section flags and scan all
sections that are allocated, writable and not executable. Which should
cover all sections of a module that might reference data.

Signed-off-by: Steven Rostedt 
[catalin.marinas@arm.com: removed unused 'name' variable]
[catalin.marinas@arm.com: collapsed 'if' blocks]
Signed-off-by: Catalin Marinas 
Acked-by: Rusty Russell

module: don't unlink the module until we've removed all exposure.

2013-04-17T03:53:02+00:00

Otherwise we get a race between unload and reload of the same module:
the new module doesn't see the old one in the list, but then fails because
it can't register over the still-extant entries in sysfs:

 [  103.981925] ------------[ cut here ]------------
 [  103.986902] WARNING: at fs/sysfs/dir.c:536 sysfs_add_one+0xab/0xd0()
 [  103.993606] Hardware name: CrownBay Platform
 [  103.998075] sysfs: cannot create duplicate filename '/module/pch_gbe'
 [  104.004784] Modules linked in: pch_gbe(+) [last unloaded: pch_gbe]
 [  104.011362] Pid: 3021, comm: modprobe Tainted: G        W    3.9.0-rc5+ #5
 [  104.018662] Call Trace:
 [  104.021286]  [] warn_slowpath_common+0x6d/0xa0
 [  104.026933]  [] ? sysfs_add_one+0xab/0xd0
 [  104.031986]  [] ? sysfs_add_one+0xab/0xd0
 [  104.037000]  [] warn_slowpath_fmt+0x2e/0x30
 [  104.042188]  [] sysfs_add_one+0xab/0xd0
 [  104.046982]  [] create_dir+0x5e/0xa0
 [  104.051633]  [] sysfs_create_dir+0x78/0xd0
 [  104.056774]  [] kobject_add_internal+0x83/0x1f0
 [  104.062351]  [] ? kvasprintf+0x46/0x60
 [  104.067231]  [] kobject_add_varg+0x2d/0x50
 [  104.072450]  [] kobject_init_and_add+0x27/0x30
 [  104.078075]  [] mod_sysfs_setup+0x80/0x540
 [  104.083207]  [] ? module_bug_finalize+0x51/0xc0
 [  104.088720]  [] load_module+0x1429/0x18b0

We can teardown sysfs first, then to be sure, put the state in
MODULE_STATE_UNFORMED so it's ignored while we deconstruct it.

Reported-by: Veaceslav Falico 
Tested-by: Veaceslav Falico 
Signed-off-by: Rusty Russell