[PATCH 1/3] Cygwin: define fhandler_fifo::fstat
Ken Brown
kbrown@cornell.edu
Thu Feb 18 17:13:46 GMT 2021
Previously fstat on a FIFO would call fhandler_base::fstat.
The latter is not appropriate if fhandler_fifo::open has already been
called (and O_PATH is not set), for the following reason. If a FIFO
has been opened as a writer or duplexer, then it has an io_handle that
is a pipe handle rather than a file handle. fhandler_base::fstat will
use this handle and potentially return incorrect results. If the FIFO
has been opened as a reader, then it has no io_handle, and a call to
fhandler_base::fstat will lead to a call to fhandler_base::open.
Opening the fhandler a second time can change it in undesired ways;
for example, it can modify the flags and status_flags.
The new fhandler_fifo::fstat avoids these problems by creating an
fhandler_disk_file and calling its fstat method in case
fhandler_fifo::open has already been called and O_PATH is not set.
---
winsup/cygwin/fhandler.h | 1 +
winsup/cygwin/fhandler_fifo.cc | 23 +++++++++++++++++++++++
2 files changed, 24 insertions(+)
diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index e457e2785..78d9c7984 100644
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -1510,6 +1510,7 @@ public:
ssize_t __reg3 raw_write (const void *ptr, size_t ulen);
void fixup_after_fork (HANDLE);
void fixup_after_exec ();
+ int __reg2 fstat (struct stat *buf);
int __reg2 fstatvfs (struct statvfs *buf);
select_record *select_read (select_stuff *);
select_record *select_write (select_stuff *);
diff --git a/winsup/cygwin/fhandler_fifo.cc b/winsup/cygwin/fhandler_fifo.cc
index 8b67037cb..365f14053 100644
--- a/winsup/cygwin/fhandler_fifo.cc
+++ b/winsup/cygwin/fhandler_fifo.cc
@@ -1494,6 +1494,29 @@ errout:
len = (size_t) -1;
}
+int __reg2
+fhandler_fifo::fstat (struct stat *buf)
+{
+ if (reader || writer || duplexer)
+ {
+ /* fhandler_fifo::open has been called, and O_PATH is not set.
+ We don't want to call fhandler_base::fstat. In the writer
+ and duplexer cases we have a handle, but it's a pipe handle
+ rather than a file handle, so it's not suitable for stat. In
+ the reader case we don't have a handle, but
+ fhandler_base::fstat would call fhandler_base::open, which
+ would modify the flags and status_flags. */
+ fhandler_disk_file fh (pc);
+ fh.get_device () = FH_FS;
+ int res = fh.fstat (buf);
+ buf->st_dev = buf->st_rdev = dev ();
+ buf->st_mode = dev ().mode ();
+ buf->st_size = 0;
+ return res;
+ }
+ return fhandler_base::fstat (buf);
+}
+
int __reg2
fhandler_fifo::fstatvfs (struct statvfs *sfs)
{
--
2.30.0
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