From 9c85bcd8f5f9f775e8305e580cf5fbc5b7ba2c28 Mon Sep 17 00:00:00 2001 From: Guenter Roeck Date: Mon, 16 Mar 2020 15:52:24 +0000 Subject: [PATCH] m25p80: Improve command handling for unsupported commands MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Whenever an unsupported command is encountered, the current code interprets each transferred byte as new command. Most of the time, those 'commands' are interpreted as new unknown commands. However, in rare cases, it may be that for example address or length information passed with the original command is by itself a valid command. If that happens, the state machine may get completely confused and, worst case, start writing data into the flash or even erase it. To avoid the problem, transition into STATE_READING_DATA and keep sending a value of 0 until the chip is deselected after encountering an unsupported command. Signed-off-by: Guenter Roeck Reviewed-by: Philippe Mathieu-Daudé Reviewed-by: Cédric Le Goater Signed-off-by: Peter Maydell --- hw/block/m25p80.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/hw/block/m25p80.c b/hw/block/m25p80.c index 53bf63856f..8227088441 100644 --- a/hw/block/m25p80.c +++ b/hw/block/m25p80.c @@ -1161,6 +1161,11 @@ static void decode_new_cmd(Flash *s, uint32_t value) s->quad_enable = false; break; default: + s->pos = 0; + s->len = 1; + s->state = STATE_READING_DATA; + s->data_read_loop = true; + s->data[0] = 0; qemu_log_mask(LOG_GUEST_ERROR, "M25P80: Unknown cmd %x\n", value); break; }