powerpc: Fix bad NULL pointer check in udbg_uart_getc_poll()

commit cd32e2dcc9de6c27ecbbfc0e2079fb64b42bad5f upstream.

We have some code in udbg_uart_getc_poll() that tries to protect
against a NULL udbg_uart_in, but gets it all wrong.

Found with the LLVM static analyzer (scan-build).

Fixes: 309257484cc1 ("powerpc: Cleanup udbg_16550 and add support for LPC PIO-only UARTs")
Signed-off-by: Anton Blanchard <anton@samba.org>
[mpe: Add some newlines for readability while we're here]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/powerpc/kernel/udbg_16550.c b/arch/powerpc/kernel/udbg_16550.c
index 75702e207b2986c4741cf243c2a49c955c30e05b..f7089fcfaa5d9906e72cede1a886d29a84188ff0 100644 (file)
--- a/arch/powerpc/kernel/udbg_16550.c
+++ b/arch/powerpc/kernel/udbg_16550.c
@@ -69,8 +69,12 @@ static void udbg_uart_putc(char c)
 
 static int udbg_uart_getc_poll(void)
 {
-       if (!udbg_uart_in || !(udbg_uart_in(UART_LSR) & LSR_DR))
+       if (!udbg_uart_in)
+               return -1;
+
+       if (!(udbg_uart_in(UART_LSR) & LSR_DR))
                return udbg_uart_in(UART_RBR);
+
        return -1;
 }