Am 05.03.2013 02:05, schrieb Lennart Poettering:
> On Mon, 04.03.13 10:43, Harald Hoyer ([email protected]) wrote:
>
>> + if (initrd) {
>> + char _cleanup_free_ *mu = NULL, *name = NULL;
>> + /* Skip generation, if unit already exists */
>> + name = unit_name_from_path(where, ".mount");
>> + if (!name)
>> + return log_oom();
>> + mu = strjoin(arg_dest, "/", name, NULL);
>> + if (!mu)
>> + return log_oom();
>> +
>> + k = access(mu, R_OK);
>> + if (k == 0)
>> + continue;
>> + }
>
> Ahum. I can't say I like invocations to access() like this one. There
> are very few cases where access() is the right syscall to invoke, and I
> am pretty sure this is not one of them, due to its inherent
> raciness. There might be other generators running in parallel to this
> one, so the existance of the mount unit might have already changed by
> the time you then go on and actually create the unit file. So, your
> test here doesn't work and is pointless.
> Please folks, be very careful with access()! Uses like this are broken,
> you want to rely on O_EXCL (or fopen's "x") instead, to ensure the file
> is only created if it doesn't exist yet, and that is atomic.
>
> Quite frankly, the majority of the uses of access()es I have seen in my
> life are misuses, people really should keep the atomicity of things in mind.
>
>> static int parse_new_root_from_proc_cmdline(void) {
>> char *w, *state;
>> - _cleanup_free_ char *what = NULL, *type = NULL, *opts = NULL, *line
>> = NULL;
>> + _cleanup_free_ char *what = NULL, *type = NULL, *opts = NULL, *line
>> = NULL, *mu = NULL;
>> int r;
>> size_t l;
>>
>> + /* Skip generation, if sysroot.mount already exists */
>> + mu = strjoin(arg_dest, "/", "sysroot.mount", NULL);
>> + if (!mu)
>> + return log_oom();
>> +
>> + r = access(mu, R_OK);
>> + if (r == 0)
>> + return 0;
>> +
>
> Same here. Also: indentation is borked.
>
> Lennart
>
Sorry... reverted anyway
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