For the code that does this, see fs/dcache.c, search for
"prepend_unreachable".
Test case to demonstrate:
$ cat getcwd.c
int main(void) {
unshare(CLONE_NEWUSER | CLONE_NEWNS);
chdir("/usr");
chroot("bin");
printf("current directory: \"%s\"\n", get_current_dir_name());
char *real = realpath(".", NULL);
printf("realpath of .: \"%s\"\n", real ? real : "{none}");
real = realpath("../home/jann/.ssh", NULL);
printf("realpath of path: \"%s\"\n", real ? real : "{none}");
return 0;
}
$ cat getcwd_test.c
int main(void) {
unshare(CLONE_NEWUSER | CLONE_NEWNS);
chdir("/usr");
chroot("bin");
printf("current directory: \"%s\"\n", get_current_dir_name());
return 0;
}
$ gcc -o getcwd_test getcwd_test.c -Wall
$ ./getcwd_test
current directory: "(unreachable)/usr"
realpath.3 doesn't currently seem to handle this
case in a sane way, so I'm not going to document
its behavior yet. I'll report that as a bug instead.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The existing text was very crufty. UNIX domain sockets
support more than SOCK_STREAM for a _very_ long time now.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
madvise(2) actually returns with error EINVAL for MADV_REMOVE
when used for hugetlb VMAs, not EOPNOTSUPP, and this has been
the case since MADV_REMOVE was introduced in commit f6b3ec238d12
("madvise(MADV_REMOVE): remove pages from tmpfs shm backing
store").
Specify the exact behavior.
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The check for the slash at the start of a pathname is done in glibc
Reported-by: Fabien Pichot <fpichot@bouledef.eu>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The glibc pthread_sigqueue() function gives an error on attempts
to send either of the real-time signals used by NPTL.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The glibc pthread_kill() function gives an error on attempts
to send either of the real-time signals used by NPTL.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The glibc wrapper gives an EINVAL error on attempts to change the
disposition of either of the two real-time signals used by NPTL.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The glibc implementation silently ignores attempts to block the two
real-time signals used by NPTL.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
At the kernel level, credentials (UIDs and GIDs) are a per-thread
attribute. NPTL uses a signal-based mechanism to ensure that
when one thread changes its credentials, all other threads change
credentials to the same values. By this means, the NPTL
implementation conforms to the POSIX requirement that the threads
in a process share credentials.
Reported-by: Shawn Landden <shawn@churchofgit.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
At the kernel level, credentials (UIDs and GIDs) are a per-thread
attribute. NPTL uses a signal-based mechanism to ensure that
when one thread changes its credentials, all other threads change
credentials to the same values. By this means, the NPTL
implementation conforms to the POSIX requirement that the threads
in a process share credentials.
Reported-by: Shawn Landden <shawn@churchofgit.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
At the kernel level, credentials (UIDs and GIDs) are a per-thread
attribute. NPTL uses a signal-based mechanism to ensure that
when one thread changes its credentials, all other threads change
credentials to the same values. By this means, the NPTL
implementation conforms to the POSIX requirement that the threads
in a process share credentials.
Reported-by: Shawn Landden <shawn@churchofgit.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
At the kernel level, credentials (UIDs and GIDs) are a per-thread
attribute. NPTL uses a signal-based mechanism to ensure that
when one thread changes its credentials, all other threads change
credentials to the same values. By this means, the NPTL
implementation conforms to the POSIX requirement that the threads
in a process share credentials.
Reported-by: Shawn Landden <shawn@churchofgit.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
At the kernel level, credentials (UIDs and GIDs) are a per-thread
attribute. NPTL uses a signal-based mechanism to ensure that
when one thread changes its credentials, all other threads change
credentials to the same values. By this means, the NPTL
implementation conforms to the POSIX requirement that the threads
in a process share credentials.
Reported-by: Shawn Landden <shawn@churchofgit.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Jann Horn