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Commit 98a6f1fc02 (fs/cpio: make initramfs init script survive 'console='
kernel argument) dropped the explicit /dev/console execs for fd 0,1,2, as
they fail when booted with console= and aren't really needed as the kernel
will setup fd 0,1,2 from /dev/console before executing the initramfs anyway.
Not doing this unfortunately confuses glibc's ttyname_r(3) implementation
(used by E.G. busybox/coreutils 'tty'), causing it to fail with ENOENT as
it does a fstat on fd 0 and tries to match up st_ino / st_dev against the
entries in /dev (since glibc 2.26):
commit 15e9a4f378c8607c2ae1aa465436af4321db0e23
Author: Christian Brauner <christian.brauner@canonical.com>
Date: Fri Jan 27 15:59:59 2017 +0100
linux ttyname and ttyname_r: do not return wrong results
If a link (say /proc/self/fd/0) pointing to a device, say /dev/pts/2, in a
parent mount namespace is passed to ttyname, and a /dev/pts/2 exists (in a
different devpts) in the current namespace, then it returns /dev/pts/2.
But /dev/pts/2 is NOT the current tty, it is a different file and device.
Detect this case and return ENODEV. Userspace can choose to take this as a hint
that the fd points to a tty device but to act on the fd rather than the link.
Signed-off-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
The reason it fails is that we manually mount devtmpfs on /dev in /init, so
the /dev/console used by the kernel (in rootfs) is not the same file as
/dev/console at runtime (in devtmpfs).
Notice: Once logged in, tty does work correctly. Presumably login reopens
stdin/stdout/stderr.
To fix this, re-add the exec of /dev/console for fd 0,1,2, but only do so if
possible. Because of the above mentioned shell behaviour (specified by
POSIX [0]), perform this check in a subshell.
[0] https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_20_01
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
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