On 04/21/2017 06:11 PM, Kees Cook wrote:
On Wed, Apr 19, 2017 at 5:36 PM, Laura Abbott <labbott@xxxxxxxxxx> wrote:
On 04/19/2017 01:10 PM, Grygorii Strashko wrote:
The below backtrace can be observed on -rt kernel with CONFIG_DEBUG_RODATA
option enabled:
BUG: sleeping function called from invalid context at
kernel/locking/rtmutex.c:993
in_atomic(): 1, irqs_disabled(): 128, pid: 14, name: migration/0
1 lock held by migration/0/14:
#0: (tasklist_lock){+.+...}, at: [<c01183e8>]
update_sections_early+0x24/0xdc
irq event stamp: 38
hardirqs last enabled at (37): [<c08f6f7c>]
_raw_spin_unlock_irq+0x24/0x68
hardirqs last disabled at (38): [<c01fdfe8>] multi_cpu_stop+0xd8/0x138
softirqs last enabled at (0): [<c01303ec>]
copy_process.part.5+0x238/0x1b64
softirqs last disabled at (0): [< (null)>] (null)
Preemption disabled at: [<c01fe244>] cpu_stopper_thread+0x80/0x10c
CPU: 0 PID: 14 Comm: migration/0 Not tainted 4.9.21-rt16-02220-g49e319c
#15
Hardware name: Generic DRA74X (Flattened Device Tree)
[<c0112014>] (unwind_backtrace) from [<c010d370>] (show_stack+0x10/0x14)
[<c010d370>] (show_stack) from [<c049beb8>] (dump_stack+0xa8/0xd4)
[<c049beb8>] (dump_stack) from [<c01631a0>] (___might_sleep+0x1bc/0x2ac)
[<c01631a0>] (___might_sleep) from [<c08f7244>]
(__rt_spin_lock+0x1c/0x30)
[<c08f7244>] (__rt_spin_lock) from [<c08f77a4>] (rt_read_lock+0x54/0x68)
[<c08f77a4>] (rt_read_lock) from [<c01183e8>]
(update_sections_early+0x24/0xdc)
[<c01183e8>] (update_sections_early) from [<c01184b0>]
(__fix_kernmem_perms+0x10/0x1c)
[<c01184b0>] (__fix_kernmem_perms) from [<c01fe010>]
(multi_cpu_stop+0x100/0x138)
[<c01fe010>] (multi_cpu_stop) from [<c01fe24c>]
(cpu_stopper_thread+0x88/0x10c)
[<c01fe24c>] (cpu_stopper_thread) from [<c015edc4>]
(smpboot_thread_fn+0x174/0x31c)
[<c015edc4>] (smpboot_thread_fn) from [<c015a988>] (kthread+0xf0/0x108)
[<c015a988>] (kthread) from [<c0108818>] (ret_from_fork+0x14/0x3c)
Freeing unused kernel memory: 1024K (c0d00000 - c0e00000)
The stop_machine() is called with cpus = NULL from fix_kernmem_perms() and
mark_rodata_ro() which means only one CPU will execute
update_sections_early() while all other CPUs will spin and wait. Hence,
it's safe to remove tasklist locking from update_sections_early(). As part
of this change also mark functions which are local to this module as
static
Acked-by: Laura Abbott <labbott@xxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Please throw this at the ARM patch tracker (with our Acks).
http://www.arm.linux.org.uk/developer/patches/info.php
Done
http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=8672/1
--
regards,
-grygorii
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