Re: [libvirt] [PATCH] virt-aa-helper: Improve valid_path

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(a)redhat.com&gt; --- src/security/virt-aa-helper.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/src/security/virt-aa-helper.c b/src/security/virt-aa-helper.c index a78c4c8..b4a8f27 100644 --- a/src/security/virt-aa-helper.c +++ b/src/security/virt-aa-helper.c @@ -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; -- 2.4.6 -- libvir-list mailing list libvir-list(a)redhat.com https://www.redhat.com/mailman/listinfo/libvir-list