[newlib-cygwin] Cygwin: introduce isabspath_strict macro
Corinna Vinschen
corinna@sourceware.org
Thu Nov 11 10:03:36 GMT 2021
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=7e7d471644914397ca1e86ee99b6fc85160280c8
commit 7e7d471644914397ca1e86ee99b6fc85160280c8
Author: Corinna Vinschen <corinna@vinschen.de>
Date: Wed Nov 10 21:17:30 2021 +0100
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>
Diff:
---
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 7a48e422e..661c14347 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 f6fea6313..1f265ec28 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;
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