On 08/23/2016 08:02 PM, Rufo Dogav wrote:
This patch fixes a segfault in virt-aa-helper caused by attempting to modify a string literal in situ. It is triggered when a domain has a <filesystem> with type='mount' configured readonly, and libvirt is using the AppArmor security driver for sVirt confinement. ---
Thanks for the advice Martin - I completely overlooked the free.
src/security/virt-aa-helper.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/src/security/virt-aa-helper.c b/src/security/virt-aa-helper.c index 49e12b9..b385d8c 100644 --- a/src/security/virt-aa-helper.c +++ b/src/security/virt-aa-helper.c @@ -740,6 +740,7 @@ vah_add_path(virBufferPtr buf, const char *path, const char *perms, bool recursi bool readonly = true; bool explicit_deny_rule = true; char *sub = NULL; + char *perms_new = strdup(perms);
VIR_STRDUP Then what happens if perms_new == NULL? (eg, failure to strdup). Typically this is done via: if (VIR_STRDUP(perms_new, perms) < 0)) return -1 The other problem with what you've modified is that there's a number of places after allocation where return 0 or return rc are done, but the memory isn't free'd...
if (path == NULL) return rc; @@ -764,12 +765,12 @@ vah_add_path(virBufferPtr buf, const char *path, const char *perms, bool recursi return rc; }
Suggestion to add your VIR_STRDUP here since after here failure does the goto cleanup. John
- if (strchr(perms, 'w') != NULL) { + if (strchr(perms_new, 'w') != NULL) { readonly = false; explicit_deny_rule = false; }
- if ((sub = strchr(perms, 'R')) != NULL) { + if ((sub = strchr(perms_new, 'R')) != NULL) { /* Don't write the invalid R permission, replace it with 'r' */ sub[0] = 'r'; explicit_deny_rule = false; @@ -787,7 +788,7 @@ vah_add_path(virBufferPtr buf, const char *path, const char *perms, bool recursi if (tmp[strlen(tmp) - 1] == '/') tmp[strlen(tmp) - 1] = '\0';
- virBufferAsprintf(buf, " \"%s%s\" %s,\n", tmp, recursive ? "/**" : "", perms); + virBufferAsprintf(buf, " \"%s%s\" %s,\n", tmp, recursive ? "/**" : "", perms_new); if (explicit_deny_rule) { virBufferAddLit(buf, " # don't audit writes to readonly files\n"); virBufferAsprintf(buf, " deny \"%s%s\" w,\n", tmp, recursive ? "/**" : ""); @@ -799,6 +800,7 @@ vah_add_path(virBufferPtr buf, const char *path, const char *perms, bool recursi
cleanup: VIR_FREE(tmp); + VIR_FREE(perms_new);
return rc; }