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); if (path == NULL) return rc; @@ -764,12 +765,12 @@ vah_add_path(virBufferPtr buf, const char *path, const char *perms, bool recursi return rc; } - 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; } -- 2.9.3

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(-) 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) + goto clean_tmp; + + 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); 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; -- 2.9.3