Re: [libvirt] [PATCH] Avoid segfault in virt-aa-helper when handling read-only mount filesystems
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;
}