[Xen-changelog] Fix xenbus internal join() function to be concurrency safe

[Xen patchbot -unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID e43ffb31de480e558a1ccc7a12fbd9e2554ac83d
# Parent  90f4f4dc3f62393efc0fa01f11409065cc613c10
Fix xenbus internal join() function to be concurrency safe
(no static string buffer).

Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>

diff -r 90f4f4dc3f62 -r e43ffb31de48 
linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_xs.c
--- a/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_xs.c       Tue Oct 11 
09:33:31 2005
+++ b/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_xs.c       Tue Oct 11 
10:59:15 2005
@@ -269,18 +269,22 @@
        return num;
 }
 
-/* Return the path to dir with /name appended. */ 
+/* Return the path to dir with /name appended. Buffer must be kfree()'ed. */ 
 static char *join(const char *dir, const char *name)
 {
-       static char buffer[4096];
-
-       BUG_ON(strlen(dir) + strlen("/") + strlen(name) + 1 > sizeof(buffer));
+       char *buffer;
+
+       buffer = kmalloc(strlen(dir) + strlen("/") + strlen(name) + 1,
+                        GFP_KERNEL);
+       if (buffer == NULL)
+               return ERR_PTR(-ENOMEM);
 
        strcpy(buffer, dir);
        if (!streq(name, "")) {
                strcat(buffer, "/");
                strcat(buffer, name);
        }
+
        return buffer;
 }
 
@@ -310,10 +314,15 @@
 char **xenbus_directory(struct xenbus_transaction *t,
                        const char *dir, const char *node, unsigned int *num)
 {
-       char *strings;
+       char *strings, *path;
        unsigned int len;
 
-       strings = xs_single(t, XS_DIRECTORY, join(dir, node), &len);
+       path = join(dir, node);
+       if (IS_ERR(path))
+               return (char **)path;
+
+       strings = xs_single(t, XS_DIRECTORY, path, &len);
+       kfree(path);
        if (IS_ERR(strings))
                return (char **)strings;
 
@@ -343,7 +352,16 @@
 void *xenbus_read(struct xenbus_transaction *t,
                  const char *dir, const char *node, unsigned int *len)
 {
-       return xs_single(t, XS_READ, join(dir, node), len);
+       char *path;
+       void *ret;
+
+       path = join(dir, node);
+       if (IS_ERR(path))
+               return (void *)path;
+
+       ret = xs_single(t, XS_READ, path, len);
+       kfree(path);
+       return ret;
 }
 EXPORT_SYMBOL(xenbus_read);
 
@@ -355,15 +373,20 @@
 {
        const char *path;
        struct kvec iovec[2];
+       int ret;
 
        path = join(dir, node);
+       if (IS_ERR(path))
+               return PTR_ERR(path);
 
        iovec[0].iov_base = (void *)path;
        iovec[0].iov_len = strlen(path) + 1;
        iovec[1].iov_base = (void *)string;
        iovec[1].iov_len = strlen(string);
 
-       return xs_error(xs_talkv(t, XS_WRITE, iovec, ARRAY_SIZE(iovec), NULL));
+       ret = xs_error(xs_talkv(t, XS_WRITE, iovec, ARRAY_SIZE(iovec), NULL));
+       kfree(path);
+       return ret;
 }
 EXPORT_SYMBOL(xenbus_write);
 
@@ -371,14 +394,32 @@
 int xenbus_mkdir(struct xenbus_transaction *t,
                 const char *dir, const char *node)
 {
-       return xs_error(xs_single(t, XS_MKDIR, join(dir, node), NULL));
+       char *path;
+       int ret;
+
+       path = join(dir, node);
+       if (IS_ERR(path))
+               return PTR_ERR(path);
+
+       ret = xs_error(xs_single(t, XS_MKDIR, path, NULL));
+       kfree(path);
+       return ret;
 }
 EXPORT_SYMBOL(xenbus_mkdir);
 
 /* Destroy a file or directory (directories must be empty). */
 int xenbus_rm(struct xenbus_transaction *t, const char *dir, const char *node)
 {
-       return xs_error(xs_single(t, XS_RM, join(dir, node), NULL));
+       char *path;
+       int ret;
+
+       path = join(dir, node);
+       if (IS_ERR(path))
+               return PTR_ERR(path);
+
+       ret = xs_error(xs_single(t, XS_RM, path, NULL));
+       kfree(path);
+       return ret;
 }
 EXPORT_SYMBOL(xenbus_rm);
 

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