Nul-terminated strings are passed in all cases, so the strlen() can very
well be invoked by the function itself. In preparation for a hypervisor
change also include the nul terminator in the size calculation.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
---
Ideally libxl_flask_context_to_sid() would follow suit, but aiui doing so
would break its (stable) API.

Of course the casts in xc_flask_access() are suspicious.
---
v2: Avoid assert() use in libxl.

--- a/tools/helpers/init-xenstore-domain.c
+++ b/tools/helpers/init-xenstore-domain.c
@@ -108,7 +108,7 @@ static int build(xc_interface *xch)
 
     if ( flask )
     {
-        rv = xc_flask_context_to_sid(xch, flask, strlen(flask), &config.ssidref);
+        rv = xc_flask_context_to_sid(xch, flask, &config.ssidref);
         if ( rv )
         {
             fprintf(stderr, "xc_flask_context_to_sid failed\n");
--- a/tools/include/xenctrl.h
+++ b/tools/include/xenctrl.h
@@ -2372,7 +2372,7 @@ long xc_sharing_used_frames(xc_interface
 /*** End sharing interface ***/
 
 int xc_flask_load(xc_interface *xc_handle, char *buf, uint32_t size);
-int xc_flask_context_to_sid(xc_interface *xc_handle, char *buf, uint32_t size, uint32_t *sid);
+int xc_flask_context_to_sid(xc_interface *xc_handle, char *buf, uint32_t *sid);
 int xc_flask_sid_to_context(xc_interface *xc_handle, int sid, char *buf, uint32_t size);
 int xc_flask_getenforce(xc_interface *xc_handle);
 int xc_flask_setenforce(xc_interface *xc_handle, int mode);
--- a/tools/libs/ctrl/xc_flask.c
+++ b/tools/libs/ctrl/xc_flask.c
@@ -83,10 +83,11 @@ int xc_flask_load(xc_interface *xch, cha
     return err;
 }
 
-int xc_flask_context_to_sid(xc_interface *xch, char *buf, uint32_t size, uint32_t *sid)
+int xc_flask_context_to_sid(xc_interface *xch, char *buf, uint32_t *sid)
 {
     int err;
     struct xen_flask_op op = {};
+    size_t size = strlen(buf) + 1;
     DECLARE_HYPERCALL_BOUNCE(buf, size, XC_HYPERCALL_BUFFER_BOUNCE_IN);
 
     if ( xc_hypercall_bounce_pre(xch, buf) )
@@ -249,7 +250,7 @@ static int xc_flask_add(xc_interface *xc
     int err;
     struct xen_flask_op op = {};
 
-    err = xc_flask_context_to_sid(xch, scontext, strlen(scontext), &sid);
+    err = xc_flask_context_to_sid(xch, scontext, &sid);
     if ( err )
         return err;
 
@@ -325,10 +326,10 @@ int xc_flask_access(xc_interface *xch, c
     struct xen_flask_op op = {};
     int err;
 
-    err = xc_flask_context_to_sid(xch, (char*)scon, strlen(scon), &op.u.access.ssid);
+    err = xc_flask_context_to_sid(xch, (char*)scon, &op.u.access.ssid);
     if ( err )
         return err;
-    err = xc_flask_context_to_sid(xch, (char*)tcon, strlen(tcon), &op.u.access.tsid);
+    err = xc_flask_context_to_sid(xch, (char*)tcon, &op.u.access.tsid);
     if ( err )
         return err;
 
--- a/tools/libs/light/libxl_flask.c
+++ b/tools/libs/light/libxl_flask.c
@@ -21,7 +21,10 @@ int libxl_flask_context_to_sid(libxl_ctx
 {
     int rc;
 
-    rc = xc_flask_context_to_sid(ctx->xch, buf, len, ssidref);
+    if (len != strlen(buf))
+        return ERROR_INVAL;
+
+    rc = xc_flask_context_to_sid(ctx->xch, buf, ssidref);
 
     return rc;
 }
--- a/tools/python/xen/lowlevel/xc/xc.c
+++ b/tools/python/xen/lowlevel/xc/xc.c
@@ -1754,7 +1754,7 @@ static PyObject *pyflask_context_to_sid(
         return PyErr_SetFromErrno(xc_error_obj);
     }
 
-    ret = xc_flask_context_to_sid(xc_handle, ctx, strlen(ctx), &sid);
+    ret = xc_flask_context_to_sid(xc_handle, ctx, &sid);
 
     xc_interface_close(xc_handle);
 

On 7/1/26 10:47 AM, Jan Beulich wrote:
> Nul-terminated strings are passed in all cases, so the strlen() can very
> well be invoked by the function itself. In preparation for a hypervisor
> change also include the nul terminator in the size calculation.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> Acked-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
> ---
> Ideally libxl_flask_context_to_sid() would follow suit, but aiui doing so
> would break its (stable) API.
> 
> Of course the casts in xc_flask_access() are suspicious.
> ---
> v2: Avoid assert() use in libxl.
> 
> --- a/tools/helpers/init-xenstore-domain.c
> +++ b/tools/helpers/init-xenstore-domain.c
> @@ -108,7 +108,7 @@ static int build(xc_interface *xch)
>   
>       if ( flask )
>       {
> -        rv = xc_flask_context_to_sid(xch, flask, strlen(flask), &config.ssidref);
> +        rv = xc_flask_context_to_sid(xch, flask, &config.ssidref);
>           if ( rv )
>           {
>               fprintf(stderr, "xc_flask_context_to_sid failed\n");
> --- a/tools/include/xenctrl.h
> +++ b/tools/include/xenctrl.h
> @@ -2372,7 +2372,7 @@ long xc_sharing_used_frames(xc_interface
>   /*** End sharing interface ***/
>   
>   int xc_flask_load(xc_interface *xc_handle, char *buf, uint32_t size);
> -int xc_flask_context_to_sid(xc_interface *xc_handle, char *buf, uint32_t size, uint32_t *sid);
> +int xc_flask_context_to_sid(xc_interface *xc_handle, char *buf, uint32_t *sid);
>   int xc_flask_sid_to_context(xc_interface *xc_handle, int sid, char *buf, uint32_t size);
>   int xc_flask_getenforce(xc_interface *xc_handle);
>   int xc_flask_setenforce(xc_interface *xc_handle, int mode);
> --- a/tools/libs/ctrl/xc_flask.c
> +++ b/tools/libs/ctrl/xc_flask.c
> @@ -83,10 +83,11 @@ int xc_flask_load(xc_interface *xch, cha
>       return err;
>   }
>   
> -int xc_flask_context_to_sid(xc_interface *xch, char *buf, uint32_t size, uint32_t *sid)
> +int xc_flask_context_to_sid(xc_interface *xch, char *buf, uint32_t *sid)
>   {
>       int err;
>       struct xen_flask_op op = {};
> +    size_t size = strlen(buf) + 1;
>       DECLARE_HYPERCALL_BOUNCE(buf, size, XC_HYPERCALL_BUFFER_BOUNCE_IN);
>   
>       if ( xc_hypercall_bounce_pre(xch, buf) )
> @@ -249,7 +250,7 @@ static int xc_flask_add(xc_interface *xc
>       int err;
>       struct xen_flask_op op = {};
>   
> -    err = xc_flask_context_to_sid(xch, scontext, strlen(scontext), &sid);
> +    err = xc_flask_context_to_sid(xch, scontext, &sid);
>       if ( err )
>           return err;
>   
> @@ -325,10 +326,10 @@ int xc_flask_access(xc_interface *xch, c
>       struct xen_flask_op op = {};
>       int err;
>   
> -    err = xc_flask_context_to_sid(xch, (char*)scon, strlen(scon), &op.u.access.ssid);
> +    err = xc_flask_context_to_sid(xch, (char*)scon, &op.u.access.ssid);
>       if ( err )
>           return err;
> -    err = xc_flask_context_to_sid(xch, (char*)tcon, strlen(tcon), &op.u.access.tsid);
> +    err = xc_flask_context_to_sid(xch, (char*)tcon, &op.u.access.tsid);
>       if ( err )
>           return err;
>   
> --- a/tools/libs/light/libxl_flask.c
> +++ b/tools/libs/light/libxl_flask.c
> @@ -21,7 +21,10 @@ int libxl_flask_context_to_sid(libxl_ctx
>   {
>       int rc;
>   
> -    rc = xc_flask_context_to_sid(ctx->xch, buf, len, ssidref);
> +    if (len != strlen(buf))
> +        return ERROR_INVAL;
> +
> +    rc = xc_flask_context_to_sid(ctx->xch, buf, ssidref);
>   
>       return rc;
>   }
> --- a/tools/python/xen/lowlevel/xc/xc.c
> +++ b/tools/python/xen/lowlevel/xc/xc.c
> @@ -1754,7 +1754,7 @@ static PyObject *pyflask_context_to_sid(
>           return PyErr_SetFromErrno(xc_error_obj);
>       }
>   
> -    ret = xc_flask_context_to_sid(xc_handle, ctx, strlen(ctx), &sid);
> +    ret = xc_flask_context_to_sid(xc_handle, ctx, &sid);
>   
>       xc_interface_close(xc_handle);
>   
> 

Reviewed-by: Daniel P. Smith <dpsmith@apertussolutions.com>

On Wed, Jul 01, 2026 at 04:47:52PM +0200, Jan Beulich wrote:
> Nul-terminated strings are passed in all cases, so the strlen() can very
> well be invoked by the function itself. In preparation for a hypervisor
> change also include the nul terminator in the size calculation.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> Acked-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

Reviewed-by: Anthony PERARD <anthony.perard@vates.tech>

Thanks,


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