Commit 0f54df53d2 ("build: Remove gnulib") introduced a bug when I
rewrote existing code that used gnulib areadlink().
A missing "continue" statement on the path where fstatat(2) failed
caused fall-through to the case where it tries to use malloc(3) on the
value from the uninitialized stat buf. This caused a huge amount of
memory to be allocated, invoking the oom-killer inside the appliance.
Reported-by: Yongkui Guo
Fixes: commit 0f54df53d2
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1960217
As part of our efforts to clean up and simplify libguestfs, removing
gnulib deletes a large dependency that we mostly no longer use and
causes problems for new users trying to build the library from source.
A few modules from gnulib are still used (under a compatible license)
and these are copied into gnulib/lib/
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.
Declare most of the stringsbuf as CLEANUP_FREE_STRINGSBUF, so they are
freed completely on stack unwind: use take_stringsbuf() in return
places to take away from the stringsbuf its content, and remove all the
manual calls to free_stringslen (no more needed now).
This requires to not use free_stringslen anymore on failure in the
helper functions of stringsbuf, which now leave the content as-is (might
be still useful even on error).
This allows us to simplify the memory management of stringsbuf's, which
are not properly fully freed, fixing memory leaks in some error paths
(which were not calling free_stringslen).
The reasons to do this are twofold:
(a) It's probably a tiny bit faster.
(b) It lets us capture the real errno if the link(2) syscall fails.
The errno is also passed through guestmount, fixing RHBZ#895905:
+ guestmount -a test1.img -m /dev/sda1:/ -m /dev/sda2:/boot /tmp/mnt
+ touch /tmp/mnt/foo
+ cd /tmp/mnt
+ ln foo boot/foo
ln: failed to create hard link ‘boot/foo’ => ‘foo’: Invalid cross-device link
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
The presumption is that all file descriptors should be created with
the close-on-exec flag set. The only exception are file descriptors
that we want passed through to exec'd subprocesses (mainly pipes and
stdin/stdout/stderr).
For open calls, we pass O_CLOEXEC as an extra flag, eg:
fd = open ("foo", O_RDONLY|O_CLOEXEC);
This is a Linux-ism, but using a macro we can easily make it portable.
For sockets, similarly:
sock = socket (..., SOCK_STREAM|SOCK_CLOEXEC, ...);
For accepted sockets, we use the Linux accept4 system call which
allows flags to be supplied, but we use the Gnulib 'accept4' module to
make this portable.
For dup, dup2, we use the Linux dup3 system call, and the Gnulib
modules 'dup3' and 'cloexec'.
Previously a lot of daemon code used three variables (a string list,
'int size' and 'int alloc') to track growable strings buffers. This
commit implements a simple struct containing the same variables, but
using size_t instead of int:
struct stringsbuf {
char **argv;
size_t size;
size_t alloc;
};
Use it like this:
DECLARE_STRINGSBUF (ret);
//...
if (add_string (&ret, str) == -1)
return NULL;
//...
if (end_stringsbuf (&ret) == -1)
return NULL;
return ret.argv;
The RPC stubs already prefix the command name to error messages.
The daemon doesn't have to do this. As a (small) benefit this also
makes the daemon slightly smaller.
Code in the daemon such as:
if (argv[0] == NULL) {
reply_with_error ("passed an empty list");
return NULL;
}
now results in error messages like this:
><fs> command ""
libguestfs: error: command: passed an empty list
(whereas previously you would have seen ..command: command:..)
These three functions are very specifically designed for FUSE
support, so we can list directories efficiently. Instead of
making lots of lstat, lgetxattr and readlink calls, we can make just
three calls per directory to grab all the attributes (which we
then cache briefly).
Nearly every file-related function in daemons/*.c is affected:
Remove this pair of statements from each affected do_* function:
- NEED_ROOT (return -1);
- ABS_PATH (dir, return -1);
and change the type of the corresponding parameter to "const char *".
* src/generator.ml: Emit NEED_ROOT just once, even when there are two or
more Pathname args.
