kernel/panic: Filter out a potential trailing newline

From: Borislav Petkov <[email protected]>

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 an \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.

Signed-off-by Borislav Petkov <[email protected]>

Cc Andrew Morton <[email protected]>

Cc Kees Cook <[email protected]>

Cc "Steven Rostedt (VMware)" <[email protected]>

Cc [email protected]

---
 kernel/panic.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

kernel/panic.c +6 -3

index 8b2e002d52eb..5776d2879650 100644
@@ -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
        /*
--

2.19.0.271.gfe8321ec057f

From: Borislav Petkov <[email protected]>

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 an \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.

Signed-off-by Borislav Petkov <[email protected]>

Cc Andrew Morton <[email protected]>

Cc Kees Cook <[email protected]>

Cc "Steven Rostedt (VMware)" <[email protected]>

Cc [email protected]

---
 kernel/panic.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

kernel/panic.c +1 -1

index 8b2e002d52eb..5776d2879650 100644
@@ -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);

From: Borislav Petkov <[email protected]>

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 an \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.

Signed-off-by Borislav Petkov <[email protected]>

Cc Andrew Morton <[email protected]>

Cc Kees Cook <[email protected]>

Cc "Steven Rostedt (VMware)" <[email protected]>

Cc [email protected]

---
 kernel/panic.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

kernel/panic.c +1 -1

index 8b2e002d52eb..5776d2879650 100644
@@ -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;