Hello Carlos,
On 02/05/2018 09:34 PM, Carlos O'Donell wrote:
> Michael,
>
> With glibc fix 52a713fdd0a30e1bd79818e2e3c4ab44ddca1a94 for
> CVE-2018-1000001 (Sourceware BZ #22679) the implementation in the
> just released glibc 2.27 has been changed such that instead of
> returning "(unreachable)" the implementation now returns ENOENT
> as it would have if the current directory had been unlinked.
>
> I see that in 2015 the quirk was documented in commit
> a2ac97c78bf05a55f8f616fc39a4724372dcfa95, and this is no longer
> true with glibc 2.27, but may continue to be true in other C libraries,
> so I reference NOTES from the paragraph in the central text.
Thanks. Patch applied.
Cheers,
Michael
> Signed-off-by: Carlos O'Donell <carlos@xxxxxxxxxx>
>
> diff --git a/man3/getcwd.3 b/man3/getcwd.3
> index ff953a7d0..3c41736c9 100644
> --- a/man3/getcwd.3
> +++ b/man3/getcwd.3
> @@ -91,7 +91,9 @@ the current directory into another mount namespace.
> When dealing with paths from untrusted sources, callers of these
> functions should consider checking whether the returned path starts
> with '/' or '(' to avoid misinterpreting an unreachable path
> -as a relative path.
> +as a relative path. This is no longer true under some C libraries,
> +see
> +.BR NOTES .
> .PP
> The
> .BR getcwd ()
> @@ -270,6 +272,16 @@ generic implementation is called.
> Only in that case can
> these calls fail under Linux with
> .BR EACCES .
> +.PP
> +Since Linux commit v2.6.36 which added "(unreachable)" the glibc
> +.BR getcwd ()
> +has failed to conform to POSIX and returned a relative path when the API
> +contract requires an absolute path. With glibc 2.27 onwards this is corrected;
> +calling
> +.BR getcwd ()
> +from such a path will now result in failure with
> +.BR ENOENT .
> +
> .PP
> These functions are often used to save the location of the current working
> directory for the purpose of returning to it later.
> ---
>
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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