user/sven/linux.git/kernel/exit.c, branch v4.19.53

cgroup/pids: turn cgroup_subsys->free() into cgroup_subsys->release() to fix the accounting

2019-04-05T20:33:13Z

[ Upstream commit 51bee5abeab2058ea5813c5615d6197a23dbf041 ] The only user of cgroup_subsys->free() callback is pids_cgrp_subsys which needs pids_free() to uncharge the pid. However, ->free() is called from __put_task_struct()->cgroup_free() and this is too late. Even the trivial program which does for (;;) { int pid = fork(); assert(pid >= 0); if (pid) wait(NULL); else exit(0); } can run out of limits because release_task()->call_rcu(delayed_put_task_struct) implies an RCU gp after the task/pid goes away and before the final put(). Test-case: mkdir -p /tmp/CG mount -t cgroup2 none /tmp/CG echo '+pids' > /tmp/CG/cgroup.subtree_control mkdir /tmp/CG/PID echo 2 > /tmp/CG/PID/pids.max perl -e 'while ($p = fork) { wait; } $p // die "fork failed: $!\n"' & echo $! > /tmp/CG/PID/cgroup.procs Without this patch the forking process fails soon after migration. Rename cgroup_subsys->free() to cgroup_subsys->release() and move the callsite into the new helper, cgroup_release(), called by release_task() which actually frees the pid(s). Reported-by: Herton R. Krzesinski Reported-by: Jan Stancek Signed-off-by: Oleg Nesterov Signed-off-by: Tejun Heo Signed-off-by: Sasha Levin

sched/wait: Fix rcuwait_wake_up() ordering

2019-03-05T16:58:49Z

[ Upstream commit 6dc080eeb2ba01973bfff0d79844d7a59e12542e ] For some peculiar reason rcuwait_wake_up() has the right barrier in the comment, but not in the code. This mistake has been observed to cause a deadlock in the following situation: P1 P2 percpu_up_read() percpu_down_write() rcu_sync_is_idle() // false rcu_sync_enter() ... __percpu_up_read() [S] ,- __this_cpu_dec(*sem->read_count) | smp_rmb(); [L] | task = rcu_dereference(w->task) // NULL | | [S] w->task = current | smp_mb(); | [L] readers_active_check() // fail `-> Where the smp_rmb() (obviously) fails to constrain the store. [ peterz: Added changelog. ] Signed-off-by: Prateek Sood Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Andrea Parri Acked-by: Davidlohr Bueso Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: 8f95c90ceb54 ("sched/wait, RCU: Introduce rcuwait machinery") Link: https://lkml.kernel.org/r/1543590656-7157-1-git-send-email-prsood@codeaurora.org Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin

kernel/exit.c: release ptraced tasks before zap_pid_ns_processes

2019-02-06T16:30:14Z

commit 8fb335e078378c8426fabeed1ebee1fbf915690c upstream. Currently, exit_ptrace() adds all ptraced tasks in a dead list, then zap_pid_ns_processes() waits on all tasks in a current pidns, and only then are tasks from the dead list released. zap_pid_ns_processes() can get stuck on waiting tasks from the dead list. In this case, we will have one unkillable process with one or more dead children. Thanks to Oleg for the advice to release tasks in find_child_reaper(). Link: http://lkml.kernel.org/r/20190110175200.12442-1-avagin@gmail.com Fixes: 7c8bd2322c7f ("exit: ptrace: shift "reap dead" code from exit_ptrace() to forget_original_parent()") Signed-off-by: Andrei Vagin Signed-off-by: Oleg Nesterov Cc: "Eric W. Biederman" Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

signal: Pass pid type into group_send_sig_info

2018-07-21T17:57:35Z

This passes the information we already have at the call sight into group_send_sig_info. Ultimatelly allowing for to better handle signals sent to a group of processes. Signed-off-by: "Eric W. Biederman"

pid: Implement PIDTYPE_TGID

2018-07-21T15:43:12Z

Everywhere except in the pid array we distinguish between a tasks pid and a tasks tgid (thread group id). Even in the enumeration we want that distinction sometimes so we have added __PIDTYPE_TGID. With leader_pid we almost have an implementation of PIDTYPE_TGID in struct signal_struct. Add PIDTYPE_TGID as a first class member of the pid_type enumeration and into the pids array. Then remove the __PIDTYPE_TGID special case and the leader_pid in signal_struct. The net size increase is just an extra pointer added to struct pid and an extra pair of pointers of an hlist_node added to task_struct. The effect on code maintenance is the removal of a number of special cases today and the potential to remove many more special cases as PIDTYPE_TGID gets used to it's fullest. The long term potential is allowing zombie thread group leaders to exit, which will remove a lot more special cases in the code. Signed-off-by: "Eric W. Biederman"

pids: Move task_pid_type into sched/signal.h

2018-07-21T15:43:12Z

The function is general and inline so there is no need to hide it inside of exit.c Signed-off-by: "Eric W. Biederman"

kernel: use kernel_wait4() instead of sys_wait4()

2018-04-02T18:14:51Z

All call sites of sys_wait4() set *rusage to NULL. Therefore, there is no need for the copy_to_user() handling of *rusage, and we can use kernel_wait4() directly. This patch is part of a series which removes in-kernel calls to syscalls. On this basis, the syscall entry path can be streamlined. For details, see http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net Acked-by: Luis R. Rodriguez Cc: Al Viro Cc: Andrew Morton Signed-off-by: Dominik Brodowski

kernel/exit.c: export abort() to modules

2018-01-05T00:45:09Z

gcc -fisolate-erroneous-paths-dereference can generate calls to abort() from modular code too. [arnd@arndb.de: drop duplicate exports of abort()] Link: http://lkml.kernel.org/r/20180102103311.706364-1-arnd@arndb.de Reported-by: Vineet Gupta Cc: Sudip Mukherjee Cc: Arnd Bergmann Cc: Alexey Brodkin Cc: Russell King Cc: Jose Abreu Signed-off-by: Andrew Morton Signed-off-by: Arnd Bergmann Signed-off-by: Linus Torvalds

arch: define weak abort()

2017-12-15T00:00:49Z

gcc toggle -fisolate-erroneous-paths-dereference (default at -O2 onwards) isolates faulty code paths such as null pointer access, divide by zero etc. If gcc port doesnt implement __builtin_trap, an abort() is generated which causes kernel link error. In this case, gcc is generating abort due to 'divide by zero' in lib/mpi/mpih-div.c. Currently 'frv' and 'arc' are failing. Previously other arch was also broken like m32r was fixed by commit d22e3d69ee1a ("m32r: fix build failure"). Let's define this weak function which is common for all arch and fix the problem permanently. We can even remove the arch specific 'abort' after this is done. Link: http://lkml.kernel.org/r/1513118956-8718-1-git-send-email-sudipm.mukherjee@gmail.com Signed-off-by: Sudip Mukherjee Cc: Alexey Brodkin Cc: Vineet Gupta Cc: Sudip Mukherjee Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE()

2017-10-25T09:01:08Z

Please do not apply this to mainline directly, instead please re-run the coccinelle script shown below and apply its output. For several reasons, it is desirable to use {READ,WRITE}_ONCE() in preference to ACCESS_ONCE(), and new code is expected to use one of the former. So far, there's been no reason to change most existing uses of ACCESS_ONCE(), as these aren't harmful, and changing them results in churn. However, for some features, the read/write distinction is critical to correct operation. To distinguish these cases, separate read/write accessors must be used. This patch migrates (most) remaining ACCESS_ONCE() instances to {READ,WRITE}_ONCE(), using the following coccinelle script: ---- // Convert trivial ACCESS_ONCE() uses to equivalent READ_ONCE() and // WRITE_ONCE() // $ make coccicheck COCCI=/home/mark/once.cocci SPFLAGS="--include-headers" MODE=patch virtual patch @ depends on patch @ expression E1, E2; @@ - ACCESS_ONCE(E1) = E2 + WRITE_ONCE(E1, E2) @ depends on patch @ expression E; @@ - ACCESS_ONCE(E) + READ_ONCE(E) ---- Signed-off-by: Mark Rutland Signed-off-by: Paul E. McKenney Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: davem@davemloft.net Cc: linux-arch@vger.kernel.org Cc: mpe@ellerman.id.au Cc: shuah@kernel.org Cc: snitzer@redhat.com Cc: thor.thayer@linux.intel.com Cc: tj@kernel.org Cc: viro@zeniv.linux.org.uk Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/1508792849-3115-19-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar