From b56b4d7fd85b4caa04593b20320468de12bfcec3 Mon Sep 17 00:00:00 2001 From: Corinna Vinschen Date: Wed, 12 Jul 2023 13:47:49 +0200 Subject: [PATCH] Cygwin: Fix and streamline AT_EMPTY_PATH handling The GLIBC extension AT_EMPTY_PATH allows the functions fchownat and fstatat to operate on dirfd alone, if the given pathname is an empty string. This also allows to operate on any file type, not only directories. Commit fa84aa4dd2fb4 broke this. It only allows dirfd to be a directory in calls to these two functions. Fix that by handling AT_EMPTY_PATH right in gen_full_path_at. A valid dirfd and an empty pathname is now a valid combination and, noticably, this returns a valid path in path_ret. That in turn allows to remove the additional path generation code from the callers. Fixes: fa84aa4dd2fb ("Cygwin: fix errno values set by readlinkat") Reported-by: Johannes Schindelin Tested-by: Johannes Schindelin Signed-off-by: Corinna Vinschen --- winsup/cygwin/syscalls.cc | 47 +++++++++------------------------------ 1 file changed, 11 insertions(+), 36 deletions(-) diff --git a/winsup/cygwin/syscalls.cc b/winsup/cygwin/syscalls.cc index 33cf4f072..a0ad3c2d0 100644 --- a/winsup/cygwin/syscalls.cc +++ b/winsup/cygwin/syscalls.cc @@ -4439,7 +4439,7 @@ gen_full_path_at (char *path_ret, int dirfd, const char *pathname, cygheap_fdget cfd (dirfd); if (cfd < 0) return -1; - if (!cfd->pc.isdir ()) + if (!cfd->pc.isdir () && !(flags & AT_EMPTY_PATH)) { set_errno (ENOTDIR); return -1; @@ -4450,6 +4450,8 @@ gen_full_path_at (char *path_ret, int dirfd, const char *pathname, { if (!*pathname) { + if (flags & AT_EMPTY_PATH) + return 0; set_errno (ENOENT); return -1; } @@ -4571,29 +4573,14 @@ fchownat (int dirfd, const char *pathname, uid_t uid, gid_t gid, int flags) __leave; } char *path = tp.c_get (); - int res = gen_full_path_at (path, dirfd, pathname); + int res = gen_full_path_at (path, dirfd, pathname, flags); if (res) + __leave; + if (!*pathname) /* Implies AT_EMPTY_PATH */ { - if (!(errno == ENOENT && (flags & AT_EMPTY_PATH))) - __leave; - /* pathname is an empty string. Operate on dirfd. */ - if (dirfd == AT_FDCWD) - { - cwdstuff::acquire_read (); - strcpy (path, cygheap->cwd.get_posix ()); - cwdstuff::release_read (); - } - else - { - cygheap_fdget cfd (dirfd); - if (cfd < 0) - __leave; - strcpy (path, cfd->get_name ()); - /* If dirfd refers to a symlink (which was necessarily - opened with O_PATH | O_NOFOLLOW), we must operate - directly on that symlink.. */ - flags = AT_SYMLINK_NOFOLLOW; - } + /* If dirfd refers to a symlink (which was necessarily opened with + O_PATH | O_NOFOLLOW), we must operate directly on that symlink. */ + flags = AT_SYMLINK_NOFOLLOW; } return chown_worker (path, (flags & AT_SYMLINK_NOFOLLOW) ? PC_SYM_NOFOLLOW : PC_SYM_FOLLOW, uid, gid); @@ -4616,21 +4603,9 @@ fstatat (int dirfd, const char *__restrict pathname, struct stat *__restrict st, __leave; } char *path = tp.c_get (); - int res = gen_full_path_at (path, dirfd, pathname); + int res = gen_full_path_at (path, dirfd, pathname, flags); if (res) - { - if (!(errno == ENOENT && (flags & AT_EMPTY_PATH))) - __leave; - /* pathname is an empty string. Operate on dirfd. */ - if (dirfd == AT_FDCWD) - { - cwdstuff::acquire_read (); - strcpy (path, cygheap->cwd.get_posix ()); - cwdstuff::release_read (); - } - else - return fstat (dirfd, st); - } + __leave; path_conv pc (path, ((flags & AT_SYMLINK_NOFOLLOW) ? PC_SYM_NOFOLLOW : PC_SYM_FOLLOW) | PC_POSIX | PC_KEEP_HANDLE, stat_suffixes);