[systemd-devel] [PATCH] systemd-bootchart: Prevent closing random file descriptors

Daniel Mack daniel at zonque.org
Sun Mar 29 08:17:47 PDT 2015

Hi Alexander,

On 03/29/2015 03:04 PM, Alexander Sverdlin wrote:
> On 29/03/15 13:44, Daniel Mack wrote:
>>> @@ -184,6 +185,7 @@ vmstat_next:
>>>> n = pread(schedstat, buf, sizeof(buf) - 1, 0); if (n <= 0) { 
>>>> close(schedstat); +                schedstat = 0;
>> Note that 0 is a valid file descriptor number. You should really
>> rather reset the variables to -1 and check for '>= 0'. This applies
>> to all hunks of this patch, which also needs a rebase onto the
>> current git HEAD.
> I believe, it was HEAD as of time of patch submission, but I can of
> course rebase it once again. Regarding 0: everywhere in the program
> it relies on the fact that newly allocated memory is zeroed and files
> are only opened if the corresponding file descriptor field of a
> structure is 0. So do you propose to change the logic everywhere
> where the files are opened?

I see. As that code doesn't close stdin, 0 can't be returned by any
open*(), so that's not a real issues, but all code should still be
written in a way that it treats 0 as valid descriptor. So we need to
explicitly initialize fd variables to -1 after new0(), and refactor code
to where necessary.


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