linux/kernel/kmod.c, branch v3.9

Merge branch 'master' into for-3.9-async

2013-01-23T17:31:01Z

To receive f56c3196f251012de9b3ebaff55732a9074fdaae ("async: fix __lowest_in_progress()"). Signed-off-by: Tejun Heo

async, kmod: warn on synchronous request_module() from async workers

2013-01-23T00:48:03Z

Synchronous requet_module() from an async worker can lead to deadlock because module init path may invoke async_synchronize_full(). The async worker waits for request_module() to complete and the module loading waits for the async task to finish. This bug happened in the block layer because of default elevator auto-loading. Block layer has been updated not to do default elevator auto-loading and it has been decided to disallow synchronous request_module() from async workers. Trigger WARN_ON_ONCE() on synchronous request_module() from async workers. For more details, please refer to the following thread. http://thread.gmane.org/gmane.linux.kernel/1420814 Signed-off-by: Tejun Heo Reported-by: Alex Riesen Cc: Linus Torvalds Cc: Arjan van de Ven

Bury the conditionals from kernel_thread/kernel_execve series

2012-12-19T23:07:38Z

All architectures have CONFIG_GENERIC_KERNEL_THREAD CONFIG_GENERIC_KERNEL_EXECVE __ARCH_WANT_SYS_EXECVE None of them have __ARCH_WANT_KERNEL_EXECVE and there are only two callers of kernel_execve() (which is a trivial wrapper for do_execve() now) left. Kill the conditionals and make both callers use do_execve(). Signed-off-by: Al Viro

infrastructure for saner ret_from_kernel_thread semantics

2012-10-12T17:35:07Z

* allow kernel_execve() leave the actual return to userland to caller (selected by CONFIG_GENERIC_KERNEL_EXECVE). Callers updated accordingly. * architecture that does select GENERIC_KERNEL_EXECVE in its Kconfig should have its ret_from_kernel_thread() do this: call schedule_tail call the callback left for it by copy_thread(); if it ever returns, that's because it has just done successful kernel_execve() jump to return from syscall IOW, its only difference from ret_from_fork() is that it does call the callback. * such an architecture should also get rid of ret_from_kernel_execve() and __ARCH_WANT_KERNEL_EXECVE This is the last part of infrastructure patches in that area - from that point on work on different architectures can live independently. Signed-off-by: Al Viro

make sure that kernel_thread() callbacks call do_exit() themselves

2012-10-12T01:42:36Z

Most of them never returned anyway - only two functions had to be changed. That allows to simplify their callers a whole lot. Note that this does *not* apply to kthread_run() callbacks - all of those had been called from the same kernel_thread() callback, which did do_exit() already. This is strictly about very few low-level kernel_thread() callbacks (there are only 6 of those, mostly as part of kthread.h and kmod.h exported mechanisms, plus kernel_init() itself). Signed-off-by: Al Viro

kmod: avoid deadlock from recursive kmod call

2012-07-31T00:25:20Z

The system deadlocks (at least since 2.6.10) when call_usermodehelper(UMH_WAIT_EXEC) request triggers call_usermodehelper(UMH_WAIT_PROC) request. This is because "khelper thread is waiting for the worker thread at wait_for_completion() in do_fork() since the worker thread was created with CLONE_VFORK flag" and "the worker thread cannot call complete() because do_execve() is blocked at UMH_WAIT_PROC request" and "the khelper thread cannot start processing UMH_WAIT_PROC request because the khelper thread is waiting for the worker thread at wait_for_completion() in do_fork()". The easiest example to observe this deadlock is to use a corrupted /sbin/hotplug binary (like shown below). # : > /tmp/dummy # chmod 755 /tmp/dummy # echo /tmp/dummy > /proc/sys/kernel/hotplug # modprobe whatever call_usermodehelper("/tmp/dummy", UMH_WAIT_EXEC) is called from kobject_uevent_env() in lib/kobject_uevent.c upon loading/unloading a module. do_execve("/tmp/dummy") triggers a call to request_module("binfmt-0000") from search_binary_handler() which in turn calls call_usermodehelper(UMH_WAIT_PROC). In order to avoid deadlock, as a for-now and easy-to-backport solution, do not try to call wait_for_completion() in call_usermodehelper_exec() if the worker thread was created by khelper thread with CLONE_VFORK flag. Future and fundamental solution might be replacing singleton khelper thread with some workqueue so that recursive calls up to max_active dependency loop can be handled without deadlock. [akpm@linux-foundation.org: add comment to kmod_thread_locker] Signed-off-by: Tetsuo Handa Cc: Arjan van de Ven Acked-by: Rusty Russell Cc: Tejun Heo Cc: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kernel/kmod.c: document call_usermodehelper_fns() a bit

2012-07-31T00:25:20Z

This function's interface is, uh, subtle. Attempt to apologise for it. Cc: WANG Cong Cc: Cyrill Gorcunov Cc: Kees Cook Cc: Serge Hallyn Cc: "Eric W. Biederman" Cc: Alan Cox Cc: Oleg Nesterov Cc: Rusty Russell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kmod.c: fix kernel-doc warning

2012-06-01T00:49:28Z

Warning(kernel/kmod.c:419): No description found for parameter 'depth' Signed-off-by: Randy Dunlap Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kmod: move call_usermodehelper_fns() to .c file and unexport all it's helpers

2012-06-01T00:49:28Z

If we move call_usermodehelper_fns() to kmod.c file and EXPORT_SYMBOL it we can avoid exporting all it's helper functions: call_usermodehelper_setup call_usermodehelper_setfns call_usermodehelper_exec And make all of them static to kmod.c Since the optimizer will see all these as a single call site it will inline them inside call_usermodehelper_fns(). So we loose the call to _fns but gain 3 calls to the helpers. (Not that it matters) Signed-off-by: Boaz Harrosh Cc: Oleg Nesterov Cc: Tetsuo Handa Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kmod: unexport call_usermodehelper_freeinfo()

2012-06-01T00:49:28Z

call_usermodehelper_freeinfo() is not used outside of kmod.c. So unexport it, and make it static to kmod.c Signed-off-by: Boaz Harrosh Cc: Oleg Nesterov Cc: Tetsuo Handa Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds