From: Corinna Vinschen <cori...@vinschen.de> isabspath handles a path "X:", without trailing slas 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 <cori...@vinschen.de> --- winsup/cygwin/syscalls.cc | 2 +- winsup/cygwin/winsup.h | 8 ++++++++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/winsup/cygwin/syscalls.cc b/winsup/cygwin/syscalls.cc index 7a48e422e8f4..661c143479e4 100644 --- a/winsup/cygwin/syscalls.cc +++ b/winsup/cygwin/syscalls.cc @@ -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 { diff --git a/winsup/cygwin/winsup.h b/winsup/cygwin/winsup.h index f6fea6313d56..1f265ec28934 100644 --- a/winsup/cygwin/winsup.h +++ b/winsup/cygwin/winsup.h @@ -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; -- 2.31.1