Cygwin: introduce isabspath_strict macro

isabspath handles a path "X:", without trailing slash or backslash,
as absolute path.  This breaks some scenarios with relative paths
starting with "X:".  For instance, fstatat will mishandle a call
with valid dirfd and "c:" as path.

The reason is that gen_full_path_at() will check for isabspath("C:")
which returns true.  So the path will be used verbatim in fstatat,
rather than being converted to a path "<dirfd-path>/c:".

So, introduce isabspath_strict, which returns true for paths starting
with "X:" only if the next char is actually a slash or backslash.
Use it from gen_full_path_at().

This still fixes only half the problem.  The right thing would have been
to disallow using DOS paths in the first place.  Unfortunately it's much
too late for that.

Addresses: https://cygwin.com/pipermail/cygwin/2021-November/249837.html
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen 2021-11-10 21:17:30 +01:00
parent 8539c39172
commit e1f02dca90
2 changed files with 9 additions and 1 deletions

View File

@ -4714,7 +4714,7 @@ gen_full_path_at (char *path_ret, int dirfd, const char *pathname,
return -1;
}
}
if (pathname && isabspath (pathname))
if (pathname && isabspath_strict (pathname))
stpcpy (path_ret, pathname);
else
{

View File

@ -139,9 +139,17 @@ extern int cygserver_running;
#undef issep
#define issep(ch) (strchr (" \t\n\r", (ch)) != NULL)
/* Treats "X:" as absolute path.
FIXME: We should drop the notion that "X:" is a valid absolute path.
Only "X:/" and "X:\\" should be (see isabspath_strict below). The
problem is to find out if we have code depending on this behaviour. */
#define isabspath(p) \
(isdirsep (*(p)) || (isalpha (*(p)) && (p)[1] == ':' && (!(p)[2] || isdirsep ((p)[2]))))
/* Treats "X:/" and "X:\\" as absolute paths, but not "X:" */
#define isabspath_strict(p) \
(isdirsep (*(p)) || (isalpha (*(p)) && (p)[1] == ':' && isdirsep ((p)[2])))
/******************** Initialization/Termination **********************/
class per_process;