[ Upstream commit ec3f4e0443a61e68092ac07111f16dd4ca89ddb4 ]

initramfs_test_extract() and friends call unpack_to_rootfs() from a
kunit kthread while do_populate_rootfs() may still be running
asynchronously from rootfs_initcall. unpack_to_rootfs() keeps its
parser state in module-static variables (victim, byte_count, state,
this_header, header_buf, name_buf, ...), so the two writers corrupt
each other.

On arm64 v7.0-rc5+ this oopses early in boot:

  Unable to handle kernel paging request at virtual address ffff80018f9f0ffc
  pc : do_reset+0x3c/0x98
  Call trace:
   do_reset
   initramfs_test_extract
   kunit_try_run_case
  Initramfs unpacking failed: junk within compressed archive

do_reset() faults because 'victim' was overwritten by the boot-time
unpacker; the boot unpacker meanwhile logs the bogus "junk within
compressed archive" on the real initrd because the test wrecked its
state machine.

Add a .suite_init callback that calls wait_for_initramfs() so the async
unpack is quiescent before the first case runs. suite_init runs once per
suite rather than before every individual test case.

Fixes: 83c0b27266ec ("initramfs_test: kunit tests for initramfs unpacking")
Signed-off-by: Jia He <justin.he@arm.com>
Link: https://patch.msgid.link/20260519093937.1064628-1-justin.he@arm.com
Reviewed-by: David Disseldorp <ddiss@suse.de>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Confirm that cpio filenames with multiple trailing zeros (accounted for
in namesize) extract successfully.

Signed-off-by: David Disseldorp <ddiss@suse.de>
Acked-by: Nicolas Schier <nsc@kernel.org>
Link: https://lore.kernel.org/r/20250819032607.28727-9-ddiss@suse.de
[nathan: Fix duplicate filesize initialization, reported at
         https://lore.kernel.org/202508200304.wF1u78il-lkp@intel.com/]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Provide some basic initramfs unpack sanity tests covering:

- simple file / dir extraction
- filename field overrun, as reported and fixed separately via
  https://lore.kernel.org/r/20241030035509.20194-2-ddiss@suse.de
- "070702" cpio data checksums
- hardlinks

Signed-off-by: David Disseldorp <ddiss@suse.de>
Link: https://lore.kernel.org/r/20250304061020.9815-3-ddiss@suse.de
Signed-off-by: Christian Brauner <brauner@kernel.org>