Use "FAN_OPEN_PERM" consistently rather than "FAN_PERM_OPEN".
Signed-off-by: Anthony Iliopoulos <ailiopoulos@suse.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Because of setns() semantics, the parent of a process may reside
in the outer PID namespace. If that parent terminates, then the
child is adopted by the "init" in the outer PID namespace (rather
than the "init" of the PID namespace of the child).
Thus, in a scenario such as the following, if process M
terminates, P is adopted by the init process in the initial
PID namespace, and if P terminates, Q is adopted by the init
process in the inner PID namespace.
+---------------------------------------------+
| Initial PID NS |
| +---------------+ |
| +-+ | inner PID NS | |
| |1| | | |
| +-+ | +-+ | |
| | |1| | |
| | +-+ | |
| | | |
| +-+ setns(), fork() | +-+ | |
| |M|----------------------+--> |P| | |
| +-+ | +-+ | |
| | | fork() | |
| | v | |
| | +-+ | |
| | |Q| | |
| | +-+ | |
| +---------------+ |
+---------------------------------------------+
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Having the signals listed in three different tables reduces
readability, and would require more table splits if future
standards specify other signals.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The current tables of signal information are unwieldy,
as they try to cram in too much information.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The previous location does not seem to be getting updated.
(For example, at the time of this commit, libcap-2.26
had been out for two months, but was not present at
http://www.kernel.org/pub/linux/libs/security/linux-privs.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
x86 and ARM are the most common architectures, but currently
are in the second subfield in the signal number lists.
Instead, swap that info with subfield 1, so the most
common architectures are first in the list.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This patch adds the signal numbers for parisc to the signal(7) man page.
Those parisc-specific values for the various signals are valid since the
Linux kernel upstream commit ("parisc: Reduce SIGRTMIN from 37 to 32 to
behave like other Linux architectures") during development of kernel 3.18:
http://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1f25df2eff5b25f52c139d3ff31bc883eee9a0ab
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Mention that the named constants (SECBIT_KEEP_CAPS and others)
are available only if the linux/securebits.h user-space header
is included.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
eBPF sub-system on Linux can use "helper functions", functions
implemented in the kernel that can be called from within a eBPF program
injected by a user on Linux. The kernel already supports a long list of
such helpers (sixty-seven at this time, new ones are under review).
Therefore, it is proposed to create a new manual page, separate from
bpf(2), to document those helpers for people willing to develop new eBPF
programs.
Additionally, in an effort to keep this documentation in synchronisation
with what is implemented in the kernel, it is further proposed to keep
the documentation itself in the kernel sources, as comments in file
"include/uapi/linux/bpf.h", and to generate the man page from there.
This patch adds the new man page, generated from kernel sources, to the
man-pages repository. For each eBPF helper function, a description of
the helper, of its arguments and of the return value is provided. The
idea is that all future changes for this page should be redirected to
the kernel file "include/uapi/linux/bpf.h", and the modified page
generated from there.
Generating the page itself is a two-step process. First, the
documentation is extracted from include/uapi/linux/bpf.h, and converted
to a RST (reStructuredText-formatted) page, with the relevant script
from Linux sources:
$ ./scripts/bpf_helpers_doc.py > /tmp/bpf-helpers.rst
The second step consists in turning the RST document into the final man
page, with rst2man:
$ rst2man /tmp/bpf-helpers.rst > bpf-helpers.7
The bpf.h file was taken as at kernel 4.19
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This just adds to the point made by Marcus Gelderie's patch. Note
also that SECBIT_KEEP_CAPS provides the same functionality as the
prctl() PR_SET_KEEPCAPS flag, and the prctl(2) manual page has the
correct description of the semantics (i.e., that the flag affects
the treatment of onlt the permitted capability set).
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The description of SECBIT_KEEP_CAPS is misleading about the
effects on the effective capabilities of a process during a
switch to nonzero UIDs. The effective set is cleared based on
the effective UID switching to a nonzero value, even if
SECBIT_KEEP_CAPS is set. However, with this bit set, the
effective and permitted sets are not cleared if the real and
saved set-user-ID are set to nonzero values.
This was tested using the following C code and reading the kernel
source at security/commoncap.c: cap_emulate_setxuid.
void print_caps(void) {
cap_t current = cap_get_proc();
if (!current) {
perror("Current caps");
return;
}
char *text = cap_to_text(current, NULL);
if (!text) {
perror("Converting caps to text");
goto free_caps;
}
printf("Capabilities: %s\n", text);
cap_free(text);
free_caps:
cap_free(current);
}
void print_creds(void) {
uid_t ruid, suid, euid;
if (getresuid(&ruid, &euid, &suid)) {
perror("Error getting UIDs");
return;
}
printf("real = %d, effective = %d, saved set-user-ID = %d\n", ruid, euid, suid);
}
void set_caps(int size, const cap_value_t *caps) {
cap_t current = cap_init();
if (!current) {
perror("Error getting current caps");
return;
}
if (cap_clear(current)) {
perror("Error clearing caps");
}
if (cap_set_flag(current, CAP_INHERITABLE, size, caps, CAP_SET)) {
perror("setting caps");
goto free_caps;
}
if (cap_set_flag(current, CAP_EFFECTIVE, size, caps, CAP_SET)) {
perror("setting caps");
goto free_caps;
}
if (cap_set_flag(current, CAP_PERMITTED, size, caps, CAP_SET)) {
perror("setting caps");
goto free_caps;
}
if (cap_set_proc(current)) {
perror("Comitting caps");
goto free_caps;
}
free_caps:
cap_free(current);
}
const cap_value_t caps[] = {CAP_SETUID, CAP_SETPCAP};
const size_t num_caps = sizeof(caps) / sizeof(cap_value_t);
int main(int argc, char **argv) {
puts("[+] Dropping most capabilities to reduce amount of console output...");
set_caps(num_caps, caps);
puts("[+] Dropped capabilities. Starting with these credentials and capabilities:");
print_caps();
print_creds();
if (argc >= 2 && 0 == strncmp(argv[1], "keep", 4)) {
puts("[+] Setting SECBIT_KEEP_CAPS bit");
if (prctl(PR_SET_SECUREBITS, SECBIT_KEEP_CAPS, 0, 0, 0)) {
perror("Setting secure bits");
return 1;
}
}
puts("[+] Setting effective UID to 1000");
if (seteuid(1000)) {
perror("Error setting effective UID");
return 2;
}
print_caps();
print_creds();
puts("[+] Raising caps again");
set_caps(num_caps, caps);
print_caps();
print_creds();
puts("[+] Setting all remaining UIDs to nonzero values");
if (setreuid(1000, 1000)) {
perror("Error setting all UIDs to 1000");
return 3;
}
print_caps();
print_creds();
return 0;
}
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Prefer the word "owns" rather than "associated with" when
describing the relationship between user namespaces and non-user
namespaces. The existing text used a mix of the two terms, with
"associated with" being predominant, but to my ear, describing the
relationship as "ownership" is more comprehensible.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
There is too much detail in socket(2). Move most of it into
a new page instead.
Cowritten-by: Eugene Syromyatnikov <evgsyr@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Clarify the example by making an implied detail more explicit.
Quoting the Troy Engel on the problem with the original text:
The problem is "and a process in a sibling cgroup (sub2)"
(shown as PID 20124 here) - how did this get here? How do I
recreate this? Following this example, there's no mention of
how, it's out of place when following the instructions.
There is nothing in any of the cgroup files which contain
this (# grep freezer /proc/*/cgroup) while at this stage.
The intent is understood, however the man page seems to skip
a step to create this in the teaching example. We should add
whatever simple steps are needed to create the "process in a
sibling cgroup" as outlined so it makes sense - as written,
I have no clue where "sibling cgroup (sub2)" came from, it
just appeared out of the blue in that step. Thanks!
See https://bugzilla.kernel.org/show_bug.cgi?id=201047
Reported-by: Troy Engel <troyengel@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The intended text was hidden elsewhere in the source of the
page as a comment.
https://bugzilla.kernel.org/show_bug.cgi?id=201029
Reported-by: Mike Weilgart <mike.weilgart@verticalsysadmin.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
In particular, it is possible to write "threaded" to a
cgroup.type file if the current type is "domain threaded".
Previously, the text had implied that this was not possible.
Verified by experiment on Linux 4.15 and 4.19-rc.
Reported-by: Leah Hanson <lhanson@pivotal.io>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
After clone(CLONE_NEWPID), /proc/PID/ns/pid_for_children is empty
until the first child is created. Verified by experiment.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Michael Kerrisk