[PATCH] Avoid buffer overflow on strncat usage

[dirk@xxxxxxxx (Dirk Müller)]

strncat() does not want the total size but the maximum length.

Signed-off-by: Dirk Mueller <dmueller at suse.com>
---
 kexec/fs2dt.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kexec/fs2dt.c b/kexec/fs2dt.c
index 73c1fb9..65a8b66 100644
--- a/kexec/fs2dt.c
+++ b/kexec/fs2dt.c
@@ -649,8 +649,8 @@ static void putnode(void)
                        goto no_debug;
                }
                strncpy(filename, "/proc/device-tree/", MAXPATH);
-               strncat(filename, buff, MAXPATH);
-               strncat(filename, "/compatible", MAXPATH);
+               strncat(filename, buff, MAXPATH-strlen(filename)-1);
+               strncat(filename, "/compatible", MAXPATH-strlen(filename)-1);
                fd = open(filename, O_RDONLY);
                if (fd == -1) {
                        printf("Unable to find %s printing from
purgatory is diabled\n",
-- 
1.8.4.1