mirror of
https://github.com/libguestfs/libguestfs.git
synced 2026-03-22 07:03:38 +00:00
07c496c53c
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.
95 lines
2.4 KiB
C
95 lines
2.4 KiB
C
/* libguestfs - the guestfsd daemon
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* Copyright (C) 2010 Red Hat Inc.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <config.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "daemon.h"
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#include "actions.h"
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GUESTFSD_EXT_CMD(str_findfs, findfs);
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static char *
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findfs (const char *tag, const char *label_or_uuid)
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{
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char *out;
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CLEANUP_FREE char *err = NULL;
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CLEANUP_FREE char *arg = NULL;
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int r;
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size_t len;
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/* Kill the cache file, forcing blkid to reread values from the
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* original filesystems. In blkid there is a '-p' option which is
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* supposed to do this, but (a) it doesn't work and (b) that option
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* is not supported in RHEL 5.
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*/
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unlink ("/etc/blkid/blkid.tab");
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unlink ("/run/blkid/blkid.tab");
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if (asprintf (&arg, "%s=%s", tag, label_or_uuid) == -1) {
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reply_with_perror ("asprintf");
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return NULL;
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}
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r = command (&out, &err, str_findfs, arg, NULL);
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if (r == -1) {
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reply_with_error ("%s", err);
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free (out);
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return NULL;
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}
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/* Trim trailing \n if present. */
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len = strlen (out);
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if (len > 0 && out[len-1] == '\n')
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out[len-1] = '\0';
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if (STRPREFIX (out, "/dev/mapper/") || STRPREFIX (out, "/dev/dm-")) {
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char *canonical;
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r = lv_canonical (out, &canonical);
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if (r == -1) {
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free (out);
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return NULL;
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}
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if (r == 1) {
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free (out);
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out = canonical;
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}
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/* Ignore the case where r == 0. /dev/mapper does not correspond
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* to an LV, so the best we can do is just return it as-is.
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*/
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}
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return out; /* caller frees */
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}
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char *
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do_findfs_uuid (const char *uuid)
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{
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return findfs ("UUID", uuid);
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}
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char *
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do_findfs_label (const char *label)
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{
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return findfs ("LABEL", label);
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}
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