Re: [PATCH] coredump - as root not only if euid switched

From: Peter Waechtler
Date: Thu Apr 22 2004 - 03:53:27 EST

On Thursday, April 22, 2004, at 03:18AM, Andrew Morton <akpm@xxxxxxxx> wrote:

>Peter W�chtler <pwaechtler@xxxxxxx> wrote:
>> While it's more secure to not dump core at all if the program has
>> switched euid, it's also very unpractical. Since only programs
>> started from root, being setuid root or have CAP_SETUID it's far
>> more practical to dump as root.root mode 600. This is the bahavior
>> of Solaris.
>> The current implementation does not ensure that an existing core
>> file is only readable as root, i.e. after dumping the ownership
>> and mode is unchanged.
>> Besides mm->dumpable to avoid recursive core dumps, on setuid files
>> the dumpable flag still prevents a core dump while seteuid & co will
>> result in a core only readable as root.
>It's a bit sad to add another function call level to sys_unlink() simply
>because the core dumping code needs it.
>Is it not possible to call sys_unlink() directly from there? Something like
>long kernel_unlink(const char *name)
> mm_segment_t old_fs = get_fs();
> long ret;
> set_fs(KERNEL_DS);
> ret = sys_unlink(name);
> set_fs(old_fs);
> return ret;

And you're asking me? ;)
While getname() has a check for user/kernelspace - do you really
care about "the overhead" for a function call level with 1 argument?
Uhm, probably if you even care to write this..

What is the cost for switching the segments?
But I agree that sys_unlink should be the fast call and dumping core
is the exception :)

would fastcall do_unlink() help? I guess the arg is then passed in a

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