linux.git/fs/proc/array.c, branch v6.3

capability: just use a 'u64' instead of a 'u32[2]' array

2023-03-01T18:01:22+00:00

Back in 2008 we extended the capability bits from 32 to 64, and we did
it by extending the single 32-bit capability word from one word to an
array of two words.  It was then obfuscated by hiding the "2" behind two
macro expansions, with the reasoning being that maybe it gets extended
further some day.

That reasoning may have been valid at the time, but the last thing we
want to do is to extend the capability set any more.  And the array of
values not only causes source code oddities (with loops to deal with
it), but also results in worse code generation.  It's a lose-lose
situation.

So just change the 'u32[2]' into a 'u64' and be done with it.

We still have to deal with the fact that the user space interface is
designed around an array of these 32-bit values, but that was the case
before too, since the array layouts were different (ie user space
doesn't use an array of 32-bit values for individual capability masks,
but an array of 32-bit slices of multiple masks).

So that marshalling of data is actually simplified too, even if it does
remain somewhat obscure and odd.

This was all triggered by my reaction to the new "cap_isidentical()"
introduced recently.  By just using a saner data structure, it went from

	unsigned __capi;
	CAP_FOR_EACH_U32(__capi) {
		if (a.cap[__capi] != b.cap[__capi])
			return false;
	}
	return true;

to just being

	return a.val == b.val;

instead.  Which is rather more obvious both to humans and to compilers.

Cc: Mateusz Guzik 
Cc: Casey Schaufler 
Cc: Serge Hallyn 
Cc: Al Viro 
Cc: Paul Moore 
Signed-off-by: Linus Torvalds

Merge tag 'ucount-rlimits-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2022-10-09T23:24:05+00:00

Pull ucounts update from Eric Biederman:
 "Split rlimit and ucount values and max values

  After the ucount rlimit code was merged a bunch of small but
  siginificant bugs were found and fixed. At the time it was realized
  that part of the problem was that while the ucount rlimits were very
  similar to the oridinary ucounts (in being nested counts with limits)
  the semantics were slightly different and the code would be less error
  prone if there was less sharing.

  This is the long awaited cleanup that should hopefully keep things
  more comprehensible and less error prone for whoever needs to touch
  that code next"

* tag 'ucount-rlimits-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  ucounts: Split rlimit and ucount values and max values

proc: add some (hopefully) insightful comments

2022-07-30T01:12:35+00:00

* /proc/${pid}/net status
* removing PDE vs last close stuff (again!)
* random small stuff

Link: https://lkml.kernel.org/r/YtwrM6sDC0OQ53YB@localhost.localdomain
Signed-off-by: Alexey Dobriyan 
Signed-off-by: Andrew Morton

proc: delete unused includes

2022-07-18T00:31:39+00:00

Those aren't necessary after seq files won.

Link: https://lkml.kernel.org/r/YqnA3mS7KBt8Z4If@localhost.localdomain
Signed-off-by: Alexey Dobriyan 
Signed-off-by: Andrew Morton

ucounts: Split rlimit and ucount values and max values

2022-05-18T23:24:57+00:00

Since the semantics of maximum rlimit values are different, it would be
better not to mix ucount and rlimit values. This will prevent the error
of using inc_count/dec_ucount for rlimit parameters.

This patch also renames the functions to emphasize the lack of
connection between rlimit and ucount.

v3:
- Fix BUG:KASAN:use-after-free_in_dec_ucount.

v2:
- Fix the array-index-out-of-bounds that was found by the lkp project.

Reported-by: kernel test robot 
Signed-off-by: Alexey Gladkov 
Signed-off-by: Eric W. Biederman 
Link: https://lkml.kernel.org/r/20220518171730.l65lmnnjtnxnftpq@example.org
Signed-off-by: Eric W. Biederman

tracehook: Remove tracehook.h

2022-03-10T22:51:51+00:00

Now that all of the definitions have moved out of tracehook.h into
ptrace.h, sched/signal.h, resume_user_mode.h there is nothing left in
tracehook.h so remove it.

Update the few files that were depending upon tracehook.h to bring in
definitions to use the headers they need directly.

Reviewed-by: Kees Cook 
Link: https://lkml.kernel.org/r/20220309162454.123006-13-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman"

Merge branch 'akpm' (patches from Andrew)

2022-01-20T08:41:01+00:00

Merge more updates from Andrew Morton:
 "55 patches.

  Subsystems affected by this patch series: percpu, procfs, sysctl,
  misc, core-kernel, get_maintainer, lib, checkpatch, binfmt, nilfs2,
  hfs, fat, adfs, panic, delayacct, kconfig, kcov, and ubsan"

* emailed patches from Andrew Morton : (55 commits)
  lib: remove redundant assignment to variable ret
  ubsan: remove CONFIG_UBSAN_OBJECT_SIZE
  kcov: fix generic Kconfig dependencies if ARCH_WANTS_NO_INSTR
  lib/Kconfig.debug: make TEST_KMOD depend on PAGE_SIZE_LESS_THAN_256KB
  btrfs: use generic Kconfig option for 256kB page size limit
  arch/Kconfig: split PAGE_SIZE_LESS_THAN_256KB from PAGE_SIZE_LESS_THAN_64KB
  configs: introduce debug.config for CI-like setup
  delayacct: track delays from memory compact
  Documentation/accounting/delay-accounting.rst: add thrashing page cache and direct compact
  delayacct: cleanup flags in struct task_delay_info and functions use it
  delayacct: fix incomplete disable operation when switch enable to disable
  delayacct: support swapin delay accounting for swapping without blkio
  panic: remove oops_id
  panic: use error_report_end tracepoint on warnings
  fs/adfs: remove unneeded variable make code cleaner
  FAT: use io_schedule_timeout() instead of congestion_wait()
  hfsplus: use struct_group_attr() for memcpy() region
  nilfs2: remove redundant pointer sbufs
  fs/binfmt_elf: use PT_LOAD p_align values for static PIE
  const_structs.checkpatch: add frequently used ops structs
  ...

kthread: dynamically allocate memory to store kthread's full name

2022-01-20T06:52:53+00:00

When I was implementing a new per-cpu kthread cfs_migration, I found the
comm of it "cfs_migration/%u" is truncated due to the limitation of
TASK_COMM_LEN.  For example, the comm of the percpu thread on CPU10~19
all have the same name "cfs_migration/1", which will confuse the user.
This issue is not critical, because we can get the corresponding CPU
from the task's Cpus_allowed.  But for kthreads corresponding to other
hardware devices, it is not easy to get the detailed device info from
task comm, for example,

    jbd2/nvme0n1p2-
    xfs-reclaim/sdf

Currently there are so many truncated kthreads:

    rcu_tasks_kthre
    rcu_tasks_rude_
    rcu_tasks_trace
    poll_mpt3sas0_s
    ext4-rsv-conver
    xfs-reclaim/sd{a, b, c, ...}
    xfs-blockgc/sd{a, b, c, ...}
    xfs-inodegc/sd{a, b, c, ...}
    audit_send_repl
    ecryptfs-kthrea
    vfio-irqfd-clea
    jbd2/nvme0n1p2-
    ...

We can shorten these names to work around this problem, but it may be
not applied to all of the truncated kthreads.  Take 'jbd2/nvme0n1p2-'
for example, it is a nice name, and it is not a good idea to shorten it.

One possible way to fix this issue is extending the task comm size, but
as task->comm is used in lots of places, that may cause some potential
buffer overflows.  Another more conservative approach is introducing a
new pointer to store kthread's full name if it is truncated, which won't
introduce too much overhead as it is in the non-critical path.  Finally
we make a dicision to use the second approach.  See also the discussions
in this thread:
https://lore.kernel.org/lkml/20211101060419.4682-1-laoar.shao@gmail.com/

After this change, the full name of these truncated kthreads will be
displayed via /proc/[pid]/comm:

    rcu_tasks_kthread
    rcu_tasks_rude_kthread
    rcu_tasks_trace_kthread
    poll_mpt3sas0_statu
    ext4-rsv-conversion
    xfs-reclaim/sdf1
    xfs-blockgc/sdf1
    xfs-inodegc/sdf1
    audit_send_reply
    ecryptfs-kthread
    vfio-irqfd-cleanup
    jbd2/nvme0n1p2-8

Link: https://lkml.kernel.org/r/20211120112850.46047-1-laoar.shao@gmail.com
Signed-off-by: Yafang Shao 
Reviewed-by: David Hildenbrand 
Reviewed-by: Petr Mladek 
Suggested-by: Petr Mladek 
Suggested-by: Steven Rostedt 
Cc: Mathieu Desnoyers 
Cc: Arnaldo Carvalho de Melo 
Cc: Alexei Starovoitov 
Cc: Andrii Nakryiko 
Cc: Michal Miroslaw 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Cc: Matthew Wilcox 
Cc: Al Viro 
Cc: Kees Cook 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

exit: Use the correct exit_code in /proc//stat

2022-01-08T18:43:57+00:00

Since do_proc_statt was modified to return process wide values instead
of per task values the exit_code calculation has never been updated.
Update it now to return the process wide exit_code when it is requested
and available.

History-Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git
Fixes: bf719d26a5c1 ("[PATCH] distinct tgid/tid CPU usage")
Link: https://lkml.kernel.org/r/20220103213312.9144-4-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman"

Merge branch 'per_signal_struct_coredumps-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2021-11-03T19:15:29+00:00

Pull per signal_struct coredumps from Eric Biederman:
"Current coredumps are mixed up with the exit code, the signal handling
code, and the ptrace code making coredumps much more complicated than
necessary and difficult to follow.

This series of changes starts with ptrace_stop and cleans it up,
making it easier to follow what is happening in ptrace_stop. Then
cleans up the exec interactions with coredumps. Then cleans up the
coredump interactions with exit. Finally the coredump interactions
with the signal handling code is cleaned up.

The first and last changes are bug fixes for minor bugs.

I believe the fact that vfork followed by execve can kill the process
the called vfork if exec fails is sufficient justification to change
the userspace visible behavior.

In previous discussions some of these changes were organized
differently and individually appeared to make the code base worse. As
currently written I believe they all stand on their own as cleanups
and bug fixes.

Which means that even if the worst should happen and the last change
needs to be reverted for some unimaginable reason, the code base will
still be improved.

If the worst does not happen there are a more cleanups that can be
made. Signals that generate coredumps can easily become eligible for
short circuit delivery in complete_signal. The entire rendezvous for
generating a coredump can move into get_signal. The function
force_sig_info_to_task be written in a way that does not modify the
signal handling state of the target task (because coredumps are
eligible for short circuit delivery). Many of these future cleanups
can be done another way but nothing so cleanly as if coredumps become
per signal_struct"

* 'per_signal_struct_coredumps-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
coredump: Limit coredumps to a single thread group
coredump: Don't perform any cleanups before dumping core
exit: Factor coredump_exit_mm out of exit_mm
exec: Check for a pending fatal signal instead of core_state
ptrace: Remove the unnecessary arguments from arch_ptrace_stop
signal: Remove the bogus sigkill_pending in ptrace_stop