kernel/panic.c: filter out a potential trailing newline

If a call to panic() terminates the string with a \n , the result puts the
closing brace ']---' on a newline because panic() itself adds \n too.

Now, if one goes and removes the newline chars from all panic()
invocations - and the stats right now look like this:

~300 calls with a \n
~500 calls without a \n

one is destined to a neverending game of whack-a-mole because the usual
thing to do is add a newline at the end of a string a function is supposed
to print.

Therefore, simply zap any \n at the end of the panic string to avoid
touching so many places in the kernel.

Link: http://lkml.kernel.org/r/20181009205019.2786-1-bp@alien8.de
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/panic.c b/kernel/panic.c
index 837a94b7024d9a95ea3eeaaff78c1df6c80d9dd1..f6d549a29a5c85cfdc2de0f07e6f0e956a1268ce 100644 (file)
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -136,7 +136,7 @@ void panic(const char *fmt, ...)
 {
        static char buf[1024];
        va_list args;
-       long i, i_next = 0;
+       long i, i_next = 0, len;
        int state = 0;
        int old_cpu, this_cpu;
        bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers;
@@ -173,8 +173,12 @@ void panic(const char *fmt, ...)
        console_verbose();
        bust_spinlocks(1);
        va_start(args, fmt);
-       vsnprintf(buf, sizeof(buf), fmt, args);
+       len = vscnprintf(buf, sizeof(buf), fmt, args);
        va_end(args);
+
+       if (len && buf[len - 1] == '\n')
+               buf[len - 1] = '\0';
+
        pr_emerg("Kernel panic - not syncing: %s\n", buf);
 #ifdef CONFIG_DEBUG_BUGVERBOSE
        /*