Re: [Crash-utility] PATCH 00/10] teach crash to work with "live" ramdump
On 04/26, Dave Anderson wrote:
> Even if this module was loaded and /dev/crash existed before I start /bin/crash?
>
> # ll /dev/crash
...
> # crash ../VMLINUX
...
> # ll /dev/crash
> ls: cannot access /dev/crash: No such file or directory
>
> doesn't look friendly.
>
> And I can't use /bin/crash without root even if I do "chmod a+r
/dev/crash" on my
> machine.
>
> Is it all intentional?
Yes. The whole /dev/crash driver bullshit was put in place because of
CONFIG_STRICT_DEVMEM.
So we pretty much had to work around it by creating the read-only /dev/crash driver.
Anyway, in the original discussions, the security folks didn't want /dev/crash
hanging
around unless it was actively being used by a root-only live crash session. Later on it
was decided that the driver should be built into the kernel.
I understand the problems with /dev/crash. But I don't think /bin/crash should remove
the file created by me.
Please, just leave it be... ;-)
OK.
But why /bin/crash REMOVES /dev/crash even if this file was NOT created at startup time?
Why get_live_memory_source() doesn't even check file_exists("/dev/crash")
if
/lib/modules/%s/kernel/drivers/char/crash.ko exists?
Why I can't use /bin/crash on MY machine as non-root user even if I have the
permission
to read /dev/crash?
OK, I'll probably keep the patch below for myself. It doesn't really fix the
problems,
but it allows me to use "crash /dev/crash" on my machine without root.
Oleg.
--- x/filesys.c
+++ x/filesys.c
@@ -3859,8 +3859,7 @@ create_memory_device(dev_t dev)
/*
* It already exists -- just use it.
*/
- if ((stat.st_mode == MEMORY_DRIVER_DEVICE_MODE) &&
- (stat.st_rdev == dev))
+ if (S_ISCHR(stat.st_mode) && (stat.st_rdev == dev))
return TRUE;
/*