[RFC PATCH v3 01/10] tools: allow vchan XenStore paths more then 64 bytes long

[Dmytro Semenets <dmitry.semenets@xxxxxxxxx>]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

Current vchan implementation, while dealing with XenStore paths,
allocates 64 bytes buffer on the stack which may not be enough for
some use-cases. Make the buffer longer to respect maximum allowed
XenStore path of XENSTORE_ABS_PATH_MAX.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
Signed-off-by: Dmytro Semenets <dmytro_semenets@xxxxxxxx>
---
 tools/libs/vchan/init.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/tools/libs/vchan/init.c b/tools/libs/vchan/init.c
index 9195bd3b98..fec650dc32 100644
--- a/tools/libs/vchan/init.c
+++ b/tools/libs/vchan/init.c
@@ -249,7 +249,7 @@ static int init_xs_srv(struct libxenvchan *ctrl, int 
domain, const char* xs_base
        int ret = -1;
        struct xs_handle *xs;
        struct xs_permissions perms[2];
-       char buf[64];
+       char *buf;
        char ref[16];
        char* domid_str = NULL;
        xs_transaction_t xs_trans = XBT_NULL;
@@ -259,6 +259,10 @@ static int init_xs_srv(struct libxenvchan *ctrl, int 
domain, const char* xs_base
        if (!ctrl->xs_path)
                return -1; 
 
+       buf = malloc(XENSTORE_ABS_PATH_MAX);
+       if (!buf)
+               return -1;
+
        xs = xs_open(0);
        if (!xs)
                goto fail;
@@ -280,14 +284,14 @@ retry_transaction:
                goto fail_xs_open;
 
        snprintf(ref, sizeof ref, "%d", ring_ref);
-       snprintf(buf, sizeof buf, "%s/ring-ref", xs_base);
+       snprintf(buf, XENSTORE_ABS_PATH_MAX, "%s/ring-ref", xs_base);
        if (!xs_write(xs, xs_trans, buf, ref, strlen(ref)))
                goto fail_xs_open;
        if (!xs_set_permissions(xs, xs_trans, buf, perms, 2))
                goto fail_xs_open;
 
        snprintf(ref, sizeof ref, "%d", ctrl->event_port);
-       snprintf(buf, sizeof buf, "%s/event-channel", xs_base);
+       snprintf(buf, XENSTORE_ABS_PATH_MAX, "%s/event-channel", xs_base);
        if (!xs_write(xs, xs_trans, buf, ref, strlen(ref)))
                goto fail_xs_open;
        if (!xs_set_permissions(xs, xs_trans, buf, perms, 2))
@@ -303,6 +307,7 @@ retry_transaction:
        free(domid_str);
        xs_close(xs);
  fail:
+       free(buf);
        return ret;
 }
 
@@ -419,13 +424,20 @@ struct libxenvchan *libxenvchan_client_init(struct 
xentoollog_logger *logger,
 {
        struct libxenvchan *ctrl = malloc(sizeof(struct libxenvchan));
        struct xs_handle *xs = NULL;
-       char buf[64];
+       char *buf;
        char *ref;
        int ring_ref;
        unsigned int len;
 
        if (!ctrl)
-               return 0;
+               return NULL;
+
+       buf = malloc(XENSTORE_ABS_PATH_MAX);
+       if (!buf) {
+               free(ctrl);
+               return NULL;
+       }
+
        ctrl->ring = NULL;
        ctrl->event = NULL;
        ctrl->gnttab = NULL;
@@ -436,8 +448,9 @@ struct libxenvchan *libxenvchan_client_init(struct 
xentoollog_logger *logger,
        if (!xs)
                goto fail;
 
+
 // find xenstore entry
-       snprintf(buf, sizeof buf, "%s/ring-ref", xs_path);
+       snprintf(buf, XENSTORE_ABS_PATH_MAX, "%s/ring-ref", xs_path);
        ref = xs_read(xs, 0, buf, &len);
        if (!ref)
                goto fail;
@@ -445,7 +458,7 @@ struct libxenvchan *libxenvchan_client_init(struct 
xentoollog_logger *logger,
        free(ref);
        if (!ring_ref)
                goto fail;
-       snprintf(buf, sizeof buf, "%s/event-channel", xs_path);
+       snprintf(buf, XENSTORE_ABS_PATH_MAX, "%s/event-channel", xs_path);
        ref = xs_read(xs, 0, buf, &len);
        if (!ref)
                goto fail;
@@ -475,6 +488,7 @@ struct libxenvchan *libxenvchan_client_init(struct 
xentoollog_logger *logger,
  out:
        if (xs)
                xs_close(xs);
+       free(buf);
        return ctrl;
  fail:
        libxenvchan_close(ctrl);
-- 
2.34.1