On Tue, Mar 28, 2017 at 11:24 PM, Stefan Beller <sbel...@google.com> wrote:
> On Tue, Mar 28, 2017 at 2:15 PM, Christian Couder
> <christian.cou...@gmail.com> wrote:
>> On Sun, Mar 26, 2017 at 3:43 PM, René Scharfe <l....@web.de> wrote:
>>> FreeBSD implements getcwd(3) as a syscall, but falls back to a version
>>> based on readdir(3) if it fails for some reason. The latter requires
>>> permissions to read and execute path components, while the former does
>>> not. That means that if our buffer is too small and we're missing
>>> rights we could get EACCES, but we may succeed with a bigger buffer.
>>>
>>> Keep retrying if getcwd(3) indicates lack of permissions until our
>>> buffer can fit PATH_MAX bytes, as that's the maximum supported by the
>>> syscall on FreeBSD anyway. This way we do what we can to be able to
>>> benefit from the syscall, but we also won't loop forever if there is a
>>> real permission issue.
>>
>> Sorry to be late and maybe I missed something obvious, but the above
>> and the patch seem complex to me compared with something like:
>>
>> diff --git a/strbuf.c b/strbuf.c
>> index ace58e7367..25eadcbedc 100644
>> --- a/strbuf.c
>> +++ b/strbuf.c
>> @@ -441,7 +441,7 @@ int strbuf_readlink(struct strbuf *sb, const char
>> *path, size_t hint)
>> int strbuf_getcwd(struct strbuf *sb)
>> {
>> size_t oldalloc = sb->alloc;
>> - size_t guessed_len = 128;
>> + size_t guessed_len = PATH_MAX > 128 ? PATH_MAX : 128;
>>
>> for (;; guessed_len *= 2) {
>> strbuf_grow(sb, guessed_len);
>
> From f22a76e911 (strbuf: add strbuf_getcwd(), 2014-07-28):
> Because it doesn't use a fixed-size buffer it supports
> arbitrarily long paths, provided the platform's getcwd() does as well.
> At least on Linux and FreeBSD it handles paths longer than PATH_MAX
> just fine.
Well René's patch says:
>>> Keep retrying if getcwd(3) indicates lack of permissions until our
>>> buffer can fit PATH_MAX bytes, as that's the maximum supported by the
>>> syscall on FreeBSD anyway.
So it says that FreeBSD syscall doesn't handle paths longer than PATH_MAX.
> So with your patch, we'd still see the original issue for paths > PATH_MAX
> IIUC.
Also, René's patch just adds:
+ if (errno == EACCES && guessed_len < PATH_MAX)
+ continue;
so if the length of the path is > PATH_MAX, then guessed_len will have
to be > PATH_MAX and then René's patch will do nothing.
