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Re: [Qemu-devel] [PATCH] fw_cfg_reboot: ensure reboot_time is nonegative


From: Philippe Mathieu-Daudé
Subject: Re: [Qemu-devel] [PATCH] fw_cfg_reboot: ensure reboot_time is nonegative
Date: Thu, 25 Oct 2018 00:56:09 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1

Hi,

On 24/10/18 13:35, Laszlo Ersek wrote:
On 10/24/18 09:11, Li Qiang wrote:
This can avoid setting a negative value to
etc/boot-fail-wait.

Li Qiang, can you add a qtest for this?


Signed-off-by: Li Qiang <address@hidden>
---
  hw/nvram/fw_cfg.c | 15 ++++++++++-----
  1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index f4a52d8..276dcb1 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -199,12 +199,17 @@ static void fw_cfg_reboot(FWCfgState *s)
              reboot_timeout = strtol(p, &p, 10);
          }
      }
-    /* validate the input */
-    if (reboot_timeout > 0xffff) {
-        error_report("reboot timeout is larger than 65535, force it to 
65535.");
-        reboot_timeout = 0xffff;
+
+    if (reboot_timeout >= 0) {
+        /* validate the input */
+        if (reboot_timeout > 0xffff) {
+            error_report("reboot timeout is larger than 65535,"
+                         "force it to 65535.");
+            reboot_timeout = 0xffff;
+        }
+        fw_cfg_add_file(s, "etc/boot-fail-wait",
+                        g_memdup(&reboot_timeout, 4), 4);
      }
-    fw_cfg_add_file(s, "etc/boot-fail-wait", g_memdup(&reboot_timeout, 4), 4);
  }
static void fw_cfg_write(FWCfgState *s, uint8_t value)


I don't feel strongly about fixing this issue.

However, if we decide to fix it, we should start with the bare-bones
strtol() call, visible at the top of the context. I'm not up-to-date on
what's the best QEMU helper function for this, but I seem to remember it
checks for trailing garbage, and perhaps even for range. Maybe we should

Are you suggesting qemu_strtoul()? I agree this would be cleaner.

even use a different (better) option parsing facility thatn
qemu_opt_get(). Adding Eric and Markus.

Also, I would suggest forcing negative values (that were explicitly
specified) to some sensible positive default, such as 5 seconds or so.

Thanks
Laszlo




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