powerpc: Fix bad NULL pointer check in udbg_uart_getc_poll()

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>

1 files changed, 5 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/udbg_16550.c b/arch/powerpc/kernel/udbg_16550.c
index 6e7c4923b5ea..411116c38da4 100644
--- 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;
 }