fs/9p: avoid debug OOPS when reading a long symlink

Reading a symlink longer than the given buffer, a p9_debug use would
try to print the link name (not NUL-terminated) using a %s format.
Use %.*s instead, and replace the strncpy+strnlen with functionally
equivalent strlen+memcpy.

Signed-off-by: Jim Meyering <meyering@redhat.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index cbf9dbb1b2a2..890bed538f9b 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -1276,12 +1276,12 @@ static int v9fs_readlink(struct dentry *dentry, char *buffer, int buflen)
         }
 
         /* copy extension buffer into buffer */
-        strncpy(buffer, st->extension, buflen);
+        retval = min(strlen(st->extension)+1, (size_t)buflen);
+        memcpy(buffer, st->extension, retval);
 
-        p9_debug(P9_DEBUG_VFS, "%s -> %s (%s)\n",
-                 dentry->d_name.name, st->extension, buffer);
+        p9_debug(P9_DEBUG_VFS, "%s -> %s (%.*s)\n",
+                 dentry->d_name.name, st->extension, buflen, buffer);
 
-        retval = strnlen(buffer, buflen);
 done:
         p9stat_free(st);
         kfree(st);