Re: [PATCH 2/3] tests: Don't pass INT_MAX to virFileReadAll()

On Mon, Jun 14, 2021 at 14:30:26 +0200, Michal Prívozník wrote: > On 6/14/21 2:26 PM, Peter Krempa wrote: >> On Mon, Jun 14, 2021 at 14:14:47 +0200, Michal Prívozník wrote: >>> On 6/14/21 1:31 PM, Tim Wiederhake wrote: >>>> On Mon, 2021-06-14 at 13:06 +0200, Michal Privoznik wrote: >>>>> In a few occasions in tests we pass INT_MAX to >>>>> virFileReadLimFD(). This is not safe because virFileReadAll() >>>>> will call virFileReadLimFD() under the hood which takes the limit >>>>> and adds 1 to it. >>>> >>>> Calling virFileReadAll with "INT_MAX - 1" looks funny. Is it possible >>>> to check for "maxlen >= INT_MAX" in virFileReadLimFD instead? >>> >>> Actually, I don't understand why we need to add 1 in the first place. >>> I'll push the other two patches and send v2 for this that removes the +1. >> >> It's so that it guarantees that a file of 'maxlen' length is read >> completely and the terminating '\0' is in the resulting string. >> >> Removing the '+ 1' would change this kind of semantics, which may >> require audit of all callers. >> > > I'm not sure that's correct behaviour. I mean, if I specify that the > limit should be X, then at the most X bytes should be read, not X+1. > > Also, virFileReadLimFD() uses saferead_lim() which upon successful > return makes sure the returned string is properly terminated. saferead_lim indeed terminates the string properly. virFileReadLimFD uses the '+ 1' to see whether there are exactly "maxlen" chars in the file or potentially more than that. That's why it actually reads 1 more than the requested maximum. Whether that makes sense is obviously questionable and will require audit of all callers