We have traditionally used custom printf formatters %Q and %R, where
%Q replaces the argument with a shell-quoted string, and %R replaces
the argument with a sysroot-prefixed shell-quoted string. They are
actually pretty useful, but unfortunately only supported by glibc.
We only used them in about a dozen places in the daemon (much code
having been replaced by OCaml which does not need them).
In every remaining case we were constructing a command using code like
this:
asprintf_nowarn (&cmd,
"cd %Q && find -print0 | %s -0 -o -H %s --quiet", ...);
We can replace this with:
char *cmd;
size_t cmd_size;
fp = open_memstream (&cmd, &cmd_size);
fprintf (fp, "cd ");
shell_quote (dir, fp);
fprintf (fp, " && find -print0 | %s -0 -o -H %s --quiet", ...);
fclose (fp);
GUESTFSD_EXT_CMD was used by OpenSUSE to track which external commands
are run by the daemon and package those commands into the appliance.
It is no longer used by recent SUSE builds, so remove it.
Thanks: Pino Toscano, Olaf Hering.
GCC has two warnings related to large stack frames. We were already
using the -Wframe-larger-than warning, but this reduces the threshold
from 10000 to 5000 bytes.
However that warning only covers the static part of frames (not
alloca). So this change also enables -Wstack-usage=10000 which covers
both the static and dynamic usage (alloca and variable length arrays).
Multiple changes are made throughout the code to reduce frames to fit
within these new limits.
Note that stack allocation of large strings can be a security issue.
For example, we had code like:
size_t len = strlen (fs->windows_systemroot) + 64;
char software[len];
snprintf (software, len, "%s/system32/config/software",
fs->windows_systemroot);
where fs->windows_systemroot is guest controlled. It's not clear what
the effects might be of allowing the guest to allocate potentially
very large stack frames, but at best it allows the guest to cause
libguestfs to segfault. It turns out we are very lucky that
fs->windows_systemroot cannot be set arbitrarily large (see checks in
is_systemroot).
This commit changes those to large heap allocations instead.
Replace selected calls to 'perror (filename)' with:
fprintf (stderr, "syscall: %s: %m\n", filename);
so that more information is available about precisely which syscall
failed.
Note this is *not* reply_with_perror. These messages are only printed
in verbose output, for the benefit of debugging.
guestfsd calls many different tools. Keeping track of all of them is
error prone. This patch introduces a new helper macro to put the command
string into its own ELF section:
GUESTFSD_EXT_CMD(C_variable, command_name);
This syntax makes it still possible to grep for used command names.
The actual usage of the collected list could be like this:
objcopy -j .guestfsd_ext_cmds -O binary daemon/guestfsd /dev/stdout |
tr '\0' '\n' | sort -u
The resulting output will be used to tell mkinitrd which programs to
copy into the initrd.
Signed-off-by: Olaf Hering <olaf@aepfle.de>
RWMJ:
- Move str_vgchange at request of author.
- Fix snprintf call in daemon/debug.c
In the case where both ends cancel at the same time (eg. both ends
realize there are errors before or during the transfer), previously we
skipped sending back an error from the daemon, on the spurious basis
that the library would not need it (the library is cancelling because
of its own error).
However this is wrong: we should always send back an error message
from the daemon in order to preserve synchronization of the protocol.
A simple test case is:
$ guestfish -N fs -m /dev/sda1 upload nosuchfile /
libguestfs: error: open: nosuchfile: No such file or directory
libguestfs: error: unexpected procedure number (66/282)
(Notice two things: there are errors at both ends, and the
loss of synchronization).
After applying this commit, the loss of synchronization does not occur
and we just see the library error:
$ guestfish -N fs -m /dev/sda1 upload nosuchfile /
libguestfs: error: open: nosuchfile: No such file or directory
The choice of displaying the library or the daemon error is fairly
arbitrary in this case -- it would be valid to display either or even
to combine them into one error. Displaying the library error only
makes the code considerably simpler.
This commit also (re-)enables a test for this case.
On RHEL 5 you have to specify the -i option to get the
external 'base64' command to ignore \n characters. (The
Fedora version seems to ignore these characters anyway).
Add this option so the tests can pass on RHEL 5.
