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virt-aa-helper: Improve valid_path

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So, after some movement in virt-aa-helper, I've noticed the
virt-aa-helper-test failing. I've ran gdb (it took me a while to
realize how to do that) and this showed up immediately:

  Program received signal SIGSEGV, Segmentation fault.
  strlen () at ../sysdeps/x86_64/strlen.S:106
  106     ../sysdeps/x86_64/strlen.S: No such file or directory.
  (gdb) bt
  #0  strlen () at ../sysdeps/x86_64/strlen.S:106
  #1  0x0000555555561a13 in array_starts_with (str=0x5555557ce910 "/tmp/tmp.6nI2Fkv0KL/1.img", arr=0x7fffffffd160, size=-1540438016) at security/virt-aa-helper.c:525
  #2  0x0000555555561d49 in valid_path (path=0x5555557ce910 "/tmp/tmp.6nI2Fkv0KL/1.img", readonly=false) at security/virt-aa-helper.c:617
  #3  0x0000555555562506 in vah_add_path (buf=0x7fffffffd3e0, path=0x5555557cb910 "/tmp/tmp.6nI2Fkv0KL/1.img", perms=0x555555581585 "rw", recursive=false) at security/virt-aa-helper.c:823
  #4  0x0000555555562693 in vah_add_file (buf=0x7fffffffd3e0, path=0x5555557cb910 "/tmp/tmp.6nI2Fkv0KL/1.img", perms=0x555555581585 "rw") at security/virt-aa-helper.c:854
  #5  0x0000555555562918 in add_file_path (disk=0x5555557d4440, path=0x5555557cb910 "/tmp/tmp.6nI2Fkv0KL/1.img", depth=0, opaque=0x7fffffffd3e0) at security/virt-aa-helper.c:931
  #6  0x00007ffff78f18b1 in virDomainDiskDefForeachPath (disk=0x5555557d4440, ignoreOpenFailure=true, iter=0x5555555628a6 <add_file_path>, opaque=0x7fffffffd3e0) at conf/domain_conf.c:23286
  #7  0x0000555555562b5f in get_files (ctl=0x7fffffffd670) at security/virt-aa-helper.c:982
  #8  0x0000555555564100 in vahParseArgv (ctl=0x7fffffffd670, argc=5, argv=0x7fffffffd7e8) at security/virt-aa-helper.c:1277
  #9  0x00005555555643d6 in main (argc=5, argv=0x7fffffffd7e8) at security/virt-aa-helper.c:1332

So I've taken look at valid_path() because it is obviously
calling array_starts_with() with malformed @size. And here's the
result: there are two variables to hold the size of three arrays
and their value is recalculated before each call of
array_starts_with(). What if we just use three variables,
initialize them and do not touch them afterwards?

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
(cherry picked from commit 52970dec5b4d0fd1a9baa593b46a33bd7eeaf6b8)
This commit is contained in:
Michal Privoznik 2015-08-27 02:50:21 +02:00 committed by Cole Robinson
parent affa75e640
commit acf257deb5
1 changed files with 8 additions and 10 deletions
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18
src/security/virt-aa-helper.c
View File

@ -546,9 +546,6 @@ array_starts_with(const char *str, const char * const *arr, const long size)
static int
valid_path(const char *path, const bool readonly)
{
int npaths;
int nropaths;
const char * const restricted[] = {
"/bin/",
"/etc/",
@ -581,6 +578,10 @@ valid_path(const char *path, const bool readonly)
"/etc/libvirt-sandbox/services/" /* for virt-sandbox service config */
};
const int nropaths = ARRAY_CARDINALITY(restricted);
const int nrwpaths = ARRAY_CARDINALITY(restricted_rw);
const int nopaths = ARRAY_CARDINALITY(override);
if (path == NULL) {
vah_error(NULL, 0, _("bad pathname"));
return -1;
@ -600,21 +601,18 @@ valid_path(const char *path, const bool readonly)
vah_warning(_("path does not exist, skipping file type checks"));
/* overrides are always allowed */
npaths = sizeof(override)/sizeof(*(override));
if (array_starts_with(path, override, npaths) == 0)
if (array_starts_with(path, override, nopaths) == 0)
return 0;
/* allow read only paths upfront */
if (readonly) {
nropaths = sizeof(restricted_rw)/sizeof(*(restricted_rw));
if (array_starts_with(path, restricted_rw, nropaths) == 0)
if (array_starts_with(path, restricted_rw, nrwpaths) == 0)
return 0;
}
/* disallow RW acess to all paths in restricted and restriced_rw */
npaths = sizeof(restricted)/sizeof(*(restricted));
if ((array_starts_with(path, restricted, npaths) == 0
|| array_starts_with(path, restricted_rw, nropaths) == 0))
if ((array_starts_with(path, restricted, nropaths) == 0 ||
array_starts_with(path, restricted_rw, nrwpaths) == 0))
return 1;
return 0;