[snap] With libreoffice 5.4.0, soffice.bin is defunct after closing the application

[Olivier Tilloy]

Testing the libreoffice 5.4.0.3 snap on x86-64, the first time around the app launches fine, but after closing it it won't launch again.

This is because soffice.bin remains as a zombie process and /snap/libreoffice/current/libreoffice.wrapper never exits.

Upon inspection, the following seccomp denial is what causes the process to hang:

type=SECCOMP msg=audit(1504011042.386:4724): auid=1000 uid=1000 gid=1000 ses=4 pid=13187 comm="soffice.bin" exe="/snap/libreoffice/x4/lib/libreoffice/program/soffice.bin" sig=31 arch=c000003e syscall=94 compat=0 ip=0x7fc938d2a327 code=0x0

syscall=94 is lchown, of which there is only one call in the libreoffice codebase, in attemptChangeMetadata (sal/osl/unx/file_misc.cxx).

[Olivier Tilloy (osomon)]

When using strace (instructions at https://forum.snapcraft.io/t/stracing-snap-commands/1433), I'm seeing the app hang there:

[pid 23997] lstat("/home/osomon/snap/libreoffice/x9/.config/libreoffice/4/user/pack/database/biblio/biblio.pack", {st_dev=makedev(0, 81), st_ino=5641910, st_mode=S_IFREG|0600, st_nlink=1, st_uid=1000, st_gid=1000, st_blksize=4096, st_blocks=48, st_size=13904, st_atime=2017-08-30T09:08:36+0200.279519047, st_mtime=2017-08-30T09:07:35+0200, st_ctime=2017-08-30T09:07:35+0200.926767602}) = 0
[pid 23997] unlink("/home/osomon/snap/libreoffice/x9/.config/libreoffice/4/user/pack/database/biblio/biblio.pack") = 0
[pid 23997] rename("/tmp/nRoOht", "/home/osomon/snap/libreoffice/x9/.config/libreoffice/4/user/pack/database/biblio/biblio.pack") = -1 EXDEV (Invalid cross-device link)
[pid 23997] lstat("/tmp/nRoOht", {st_dev=makedev(0, 43), st_ino=44, st_mode=S_IFREG|0600, st_nlink=1, st_uid=1000, st_gid=1000, st_blksize=4096, st_blocks=32, st_size=13904, st_atime=2017-08-30T09:10:11+0200.116690453, st_mtime=2017-08-30T09:10:11+0200.116690453, st_ctime=2017-08-30T09:10:11+0200.116690453}) = 0
[pid 23997] stat("/home/osomon/snap/libreoffice/x9/.config/libreoffice/4/user/pack/database/biblio/biblio.pack", 0x7fff0a2ec3d0) = -1 ENOENT (No such file or directory)
[pid 23997] open("/tmp/nRoOht", O_RDONLY) = 16
[pid 23997] fstat(16, {st_dev=makedev(0, 43), st_ino=44, st_mode=S_IFREG|0600, st_nlink=1, st_uid=1000, st_gid=1000, st_blksize=4096, st_blocks=32, st_size=13904, st_atime=2017-08-30T09:10:11+0200.116690453, st_mtime=2017-08-30T09:10:11+0200.116690453, st_ctime=2017-08-30T09:10:11+0200.116690453}) = 0
[pid 23997] open("/home/osomon/snap/libreoffice/x9/.config/libreoffice/4/user/pack/database/biblio/biblio.pack", O_WRONLY|O_CREAT, 0100600) = 17
[pid 23997] pread64(16, "PACK\0\0\0\2\0\tR\tAf\344K\0\0\31\37\0\6b\222\36*\353\31\0\0\35\21"..., 13904, 0) = 13904
[pid 23997] write(17, "PACK\0\0\0\2\0\tR\tAf\344K\0\0\31\37\0\6b\222\36*\353\31\0\0\35\21"..., 13904) = 13904
[pid 23997] close(16) = 0
[pid 23997] close(17) = 0
[pid 23997] utime("/home/osomon/snap/libreoffice/x9/.config/libreoffice/4/user/pack/database/biblio/biblio.pack", {actime=2017-08-30T09:10:11+0200, modtime=2017-08-30T09:10:11+0200}) = 0
[pid 23997] getuid() = 1000
[pid 23997] lchown("/home/osomon/snap/libreoffice/x9/.config/libreoffice/4/user/pack/database/biblio/biblio.pack", 1000, 1000) = ?

[Olivier Tilloy (osomon)]

Fix/workaround: https://git.launchpad.net/~libreoffice/+git/libreoffice-snap/commit/?id=5ad0c938b72fbe5e83631535970eef137cb70932