Re: [PATCH] strbuf: support long paths w/o read rights in strbuf_getcwd() on FreeBSD

From

Christian Couder <christian.couder@gmail.com>

Date

Mar 28, 2017, 21:15 UTC

Message-ID

<CAP8UFD3pXSf+RhysULQyd2kdKSkBWdoKs+L6GPQ4jwpoeP+yOA@mail.gmail.com>

In-Reply-To

<4026bc3b-2999-9daf-d6ab-10c6d007b1e7@web.de>

On Sun, Mar 26, 2017 at 3:43 PM, René Scharfe <l.s.r@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.

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);