On 08/24/2016 07:15 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.
> ---
>
> Existing code seems to use VIR_STRDUP_QUIET for similar purposes, please
> change if VIR_STRDUP is preferred. Needed new cleanup rather than simply
> return -1; to avoid introducing leak of tmp.
>
> src/security/virt-aa-helper.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
I adjusted the commit message slightly and made the adjustments listed
below and pushed... Congrats on your first libvirt patch.
Tks
John
> diff --git a/src/security/virt-aa-helper.c b/src/security/virt-aa-helper.c
> index 49e12b9..0bcf642 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 = NULL;
>
> if (path == NULL)
> return rc;
> @@ -764,12 +765,15 @@ vah_add_path(virBufferPtr buf, const char *path, const char *perms, bool recursi
> return rc;
> }
>
> - if (strchr(perms, 'w') != NULL) {
> + if (VIR_STRDUP_QUIET(perms_new, perms) < 0)
I kept the _QUIET for this one... Printing of errors in this module is a
bit different than libvirt usually uses. The _QUIET version won't
virReportError the failed allocation.
In this case, if the allocation failed "eventually" the stack seems to
unwind to get_files() which returns failure to vahParseArgv which will
print a very generic vah_error().
-
> + goto clean_tmp;
No need to create a new label... A VIR_FREE() of something that's been
initialized to NULL doesn't do anything. A single "cleanup" label is
something that's more consistent with other libvirt code.
> +
> + 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 +791,7 @@ 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);
This is a long line - I moved perms_new to it's own line
> if (explicit_deny_rule) {
> virBufferAddLit(buf, " # don't audit writes to readonly files\n");
> virBufferAsprintf(buf, " deny \"%s%s\" w,\n", tmp, recursive ? "/**" : "");
> @@ -798,6 +802,8 @@ vah_add_path(virBufferPtr buf, const char *path, const char *perms, bool recursi
> }
>
> cleanup:
> + VIR_FREE(perms_new);
> + clean_tmp:
> VIR_FREE(tmp);
>
> return rc;
>
--
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