[Bug 2054171] [NEW] dhcpcd hook breaks when using libc6-prof's libc.so.6

[Gregory Szorc]

Public bug reported:

I have the libc6-prof package installed to provide a frame pointer
enabled libc.so.6.

I have a custom configuration file in /etc/ld.so.conf.d putting
/lib/libc6-prof/x86_64-linux-gnu at the front of the dynamic linker
search paths. (I really like having frame pointers!)

This confuses the `multiarch_dir=$(ldd /usr/sbin/dhcpcd | sed -En
's;^.*/lib/([^/]+)/libc\.so\..*$;\1;p')` line in /usr/share/initramfs-
tools/hooks/dhcpcd because the libc.so.6 path is different.

Default ldd output:

```
ldd /usr/sbin/dhcpcd
        linux-vdso.so.1 (0x00007fff9a735000)
        libcrypto.so.3 => /lib/x86_64-linux-gnu/libcrypto.so.3 (0x00007f50d2800000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f50d2400000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f50d2f27000)
```

My ldd output:

```
ldd /usr/sbin/dhcpcd
        linux-vdso.so.1 (0x00007fff802db000)
        libcrypto.so.3 => /lib/x86_64-linux-gnu/libcrypto.so.3 (0x00007fce87e00000)
        libc.so.6 => /lib/libc6-prof/x86_64-linux-gnu/libc.so.6 (0x00007fce87a00000)
        /lib64/ld-linux-x86-64.so.2 (0x00007fce88514000)
```

```
-libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f50d2400000)
+libc.so.6 => /lib/libc6-prof/x86_64-linux-gnu/libc.so.6 (0x00007fce87a00000)
```

When running the modified search paths, `ldd /usr/sbin/dhcpcd | sed -En
's;^.*/lib/([^/]+)/libc\.so\..*$;\1;p'` evaluates to an empty string and
exits 0. This results in `copy_exec "/usr/lib//dhcpcd/dev/udev.so"`,
which breaks that script.

This in turn breaks initramfs.

```
Processing triggers for linux-image-6.5.0-17-generic (6.5.0-17.17) ...
/etc/kernel/postinst.d/initramfs-tools:
update-initramfs: Generating /boot/initrd.img-6.5.0-17-generic
E: /usr/share/initramfs-tools/hooks/dhcpcd failed with return 1.
update-initramfs: failed for /boot/initrd.img-6.5.0-17-generic with 1.
run-parts: /etc/kernel/postinst.d/initramfs-tools exited with return code 1
dpkg: error processing package linux-image-6.5.0-17-generic (--configure):
 installed linux-image-6.5.0-17-generic package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
 linux-image-6.5.0-17-generic
E: Sub-process /usr/bin/dpkg returned an error code (1)
```

I can work around the issue by hacking up the dhcpcd hook or by
modifying the dynamic link path search order, running `ldconfig`, then
`update-initramfs -u`.

** Affects: initramfs-tools (Ubuntu)
     Importance: Undecided
         Status: New

** Summary changed:

- dhcpcd breaks when using libc6-prof's libc.so.6
+ dhcpcd hook breaks when using libc6-prof's libc.so.6

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https://bugs.launchpad.net/bugs/2054171

Title:
  dhcpcd hook breaks when using libc6-prof's libc.so.6

Status in initramfs-tools package in Ubuntu:
  New

Bug description:
  I have the libc6-prof package installed to provide a frame pointer
  enabled libc.so.6.

  I have a custom configuration file in /etc/ld.so.conf.d putting
  /lib/libc6-prof/x86_64-linux-gnu at the front of the dynamic linker
  search paths. (I really like having frame pointers!)

  This confuses the `multiarch_dir=$(ldd /usr/sbin/dhcpcd | sed -En
  's;^.*/lib/([^/]+)/libc\.so\..*$;\1;p')` line in /usr/share/initramfs-
  tools/hooks/dhcpcd because the libc.so.6 path is different.

  Default ldd output:

  ```
  ldd /usr/sbin/dhcpcd
          linux-vdso.so.1 (0x00007fff9a735000)
          libcrypto.so.3 => /lib/x86_64-linux-gnu/libcrypto.so.3 (0x00007f50d2800000)
          libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f50d2400000)
          /lib64/ld-linux-x86-64.so.2 (0x00007f50d2f27000)
  ```

  My ldd output:

  ```
  ldd /usr/sbin/dhcpcd
          linux-vdso.so.1 (0x00007fff802db000)
          libcrypto.so.3 => /lib/x86_64-linux-gnu/libcrypto.so.3 (0x00007fce87e00000)
          libc.so.6 => /lib/libc6-prof/x86_64-linux-gnu/libc.so.6 (0x00007fce87a00000)
          /lib64/ld-linux-x86-64.so.2 (0x00007fce88514000)
  ```

  ```
  -libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f50d2400000)
  +libc.so.6 => /lib/libc6-prof/x86_64-linux-gnu/libc.so.6 (0x00007fce87a00000)
  ```

  When running the modified search paths, `ldd /usr/sbin/dhcpcd | sed
  -En 's;^.*/lib/([^/]+)/libc\.so\..*$;\1;p'` evaluates to an empty
  string and exits 0. This results in `copy_exec
  "/usr/lib//dhcpcd/dev/udev.so"`, which breaks that script.

  This in turn breaks initramfs.

  ```
  Processing triggers for linux-image-6.5.0-17-generic (6.5.0-17.17) ...
  /etc/kernel/postinst.d/initramfs-tools:
  update-initramfs: Generating /boot/initrd.img-6.5.0-17-generic
  E: /usr/share/initramfs-tools/hooks/dhcpcd failed with return 1.
  update-initramfs: failed for /boot/initrd.img-6.5.0-17-generic with 1.
  run-parts: /etc/kernel/postinst.d/initramfs-tools exited with return code 1
  dpkg: error processing package linux-image-6.5.0-17-generic (--configure):
   installed linux-image-6.5.0-17-generic package post-installation script subprocess returned error exit status 1
  Errors were encountered while processing:
   linux-image-6.5.0-17-generic
  E: Sub-process /usr/bin/dpkg returned an error code (1)
  ```

  I can work around the issue by hacking up the dhcpcd hook or by
  modifying the dynamic link path search order, running `ldconfig`, then
  `update-initramfs -u`.

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