Reframe the discussion in terms of PTRACE_MODE_ATTACH checks,
and make a few other minor tweaks and additions.
Reviewed-by: Jann Horn <jann@thejh.net>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Among other things, Jann pointed out that the commoncap LSM
is always invoked, and Kees Cook pointed out the relevant
kernel code:
===
> BTW, can you point me at the piece(s) of kernel code that show that
> "commoncap" is always invoked in addition to any other LSM that has
> been installed?
It's not entirely obvious, but the bottom of security/commoncap.c shows:
struct security_hook_list capability_hooks[] = {
LSM_HOOK_INIT(capable, cap_capable),
...
};
void __init capability_add_hooks(void)
{
security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks));
}
And security/security.c shows the initialization order of the LSMs:
int __init security_init(void)
{
pr_info("Security Framework initialized\n");
/*
* Load minor LSMs, with the capability module always first.
*/
capability_add_hooks();
yama_add_hooks();
loadpin_add_hooks();
/*
* Load all the remaining security modules.
*/
do_security_initcalls();
return 0;
}
===
Reported-by: Jann Horn <jann@thejh.net>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The "ptrace access mode" text is about user-space-visible
behavior, but in order to explain that behavior at what I
believe is a sufficient level of detail (e.g., to differentiate
the various types of checks that are performed for various
system calls and pseudofile accesses), one needs (1) to discuss
the MODE flag details as implemented in the kernel, and (2) to
have a shorthand way to refer to the various cases from other
pages. It's not absolutely necessary to name the flags for (1),
but using the flag names is certainly a handy shorthand for (2).
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Permission to dereference/readlink /proc/PID/fd/* symlinks is
governed by a PTRACE_MODE_READ_FSCREDS ptrace access mode check.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Permission to dereference/readlink /proc/PID/ns/* symlinks is
governed by a PTRACE_MODE_READ_FSCREDS ptrace access mode check.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Permission to dereference/readlink /proc/PID/{cwd,exe,root} is
governed by a PTRACE_MODE_READ_FSCREDS ptrace access mode check.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Permission to access /proc/PID/{personality,stack,syscall} is
governed by a PTRACE_MODE_ATTACH_FSCREDS ptrace access mode check.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Permission to access /proc/PID/io is governed by
a PTRACE_MODE_READ_FSCREDS ptrace access mode check.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Permission to access /proc/PID/timerslack_ns is governed by
a PTRACE_MODE_ATTACH_FSCREDS ptrace access mode check.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Permission to access /proc/PID/{auxv,environ,wchan} is governed by
a PTRACE_MODE_READ_FSCREDS ptrace access mode check.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Permission to access /proc/PID/{maps,pagemap} is governed by a
PTRACE_MODE_READ_FSCREDS ptrace access mode check.
Permission to access /proc/PID/mem is governed by a
PTRACE_MODE_ATTACH_FSCREDS ptrace access mode check.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
At least one bit must be set in the 'val3' mask supplied for the
FUTEX_WAIT_BITSET and FUTEX_WAKE_BITSET operations.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Reported-by: Darren Hart <dvhart@infradead.org>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Michael Kerrisk