bug-coreutils
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

workaround /proc/self/fd bug on Solaris 10


From: Paul Eggert
Subject: workaround /proc/self/fd bug on Solaris 10
Date: Fri, 29 Sep 2006 17:41:20 -0700
User-agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/21.4 (gnu/linux)

I noticed that a build of CVS coreutils on Solaris 8 created
executables that didn't run on Solaris 10, because on Solaris 10
/proc/self/fd/NNN/.. is equivalent to /proc/sef/fd, not to the parent
directory of the file with descriptor NNN.  I'm not sure why Sun made
this change, but it broke the openat emulation.  I installed the
following into gnulib to work around the problem.

2006-09-29  Paul Eggert  <address@hidden>

        Work around bug in Solaris 10 /proc file system:
        /proc/self/fd/NNN/.. isn't the parent directory of
        the directory whose file descriptor is NNN.  This needs to
        be worked around at run time, not compile time, since a
        program might be built on Solaris 8, where things work, and
        run on Solaris 10.
        * lib/openat-priv.h (BUILD_PROC_NAME): Remove.  All callers changed
        to use the following interface instead:
        (OPENAT_BUFFER_SIZE): New macro.
        (openat_proc_name): New function.
        * lib/at-func.c (AT_FUNC_NAME): Adjust to above changes.
        * lib/openat.c (openat_permissive, openat_needs_fchdir, fdopendir):
        Likewise.
        * lib/openat-proc.c: New file.
        * modules/openat (Files): Add lib/openat-proc.c.
        (Depends-on): Add same-inode, stdbool.
        * m4/openat.m4 (gl_FUNC_OPENAT): Add AC_LIBOBJ(openat-proc).

Index: lib/at-func.c
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/at-func.c,v
retrieving revision 1.1
diff -p -u -r1.1 at-func.c
--- lib/at-func.c       17 Aug 2006 20:34:21 -0000      1.1
+++ lib/at-func.c       30 Sep 2006 00:35:30 -0000
@@ -39,14 +39,25 @@ AT_FUNC_NAME (int fd, char const *file A
     return CALL_FUNC (file);
 
   {
-    char *proc_file;
-    BUILD_PROC_NAME (proc_file, fd, file);
-    err = CALL_FUNC (proc_file);
-    /* If the syscall succeeds, or if it fails with an unexpected
-       errno value, then return right away.  Otherwise, fall through
-       and resort to using save_cwd/restore_cwd.  */
-    if (0 <= err || ! EXPECTED_ERRNO (errno))
-      return err;
+    char buf[OPENAT_BUFFER_SIZE];
+    char *proc_file = openat_proc_name (buf, fd, file);
+    if (proc_file)
+      {
+       int proc_result = CALL_FUNC (proc_file);
+       int proc_errno = errno;
+       if (proc_file != buf)
+         free (proc_file);
+       /* If the syscall succeeds, or if it fails with an unexpected
+          errno value, then return right away.  Otherwise, fall through
+          and resort to using save_cwd/restore_cwd.  */
+       if (0 <= proc_result)
+         return proc_result;
+       if (! EXPECTED_ERRNO (proc_errno))
+         {
+           errno = proc_errno;
+           return proc_result;
+         }
+      }
   }
 
   if (save_cwd (&saved_cwd) != 0)
Index: lib/openat-priv.h
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/openat-priv.h,v
retrieving revision 1.2
diff -p -u -r1.2 openat-priv.h
--- lib/openat-priv.h   17 Aug 2006 20:34:21 -0000      1.2
+++ lib/openat-priv.h   30 Sep 2006 00:35:30 -0000
@@ -1,5 +1,6 @@
-/* macros used by openat-like functions
-   Copyright (C) 2005 Free Software Foundation, Inc.
+/* Internals for openat-like functions.
+
+   Copyright (C) 2005, 2006 Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -17,30 +18,11 @@
 
 /* written by Jim Meyering */
 
-#include <stdio.h>
-#include <string.h>
 #include <errno.h>
-#include "alloca.h"
-#include "intprops.h"
+#include <stdlib.h>
 
-/* Set PROC_FD_FILENAME to the expansion of "/proc/self/fd/%d/%s" in
-   alloca'd memory, using FD and FILE, respectively for %d and %s. */
-#define BUILD_PROC_NAME(Proc_fd_filename, Fd, File)                    \
-  do                                                                   \
-    {                                                                  \
-      size_t filelen = strlen (File);                                  \
-      static const char procfd[] = "/proc/self/fd/%d/%s";              \
-      /* Buffer for the file name we are going to use.  It consists of \
-        - the string /proc/self/fd/                                    \
-        - the file descriptor number                                   \
-        - the file name provided.                                      \
-        The final NUL is included in the sizeof.                       \
-        Subtract 4 to account for %d and %s.  */                       \
-      size_t buflen = sizeof (procfd) - 4 + INT_STRLEN_BOUND (Fd) + filelen; \
-      (Proc_fd_filename) = alloca (buflen);                            \
-      snprintf ((Proc_fd_filename), buflen, procfd, (Fd), (File));     \
-    }                                                                  \
-  while (0)
+#define OPENAT_BUFFER_SIZE 512
+char *openat_proc_name (char buf[OPENAT_BUFFER_SIZE], int fd, char const 
*file);
 
 /* Some systems don't have ENOSYS.  */
 #ifndef ENOSYS
Index: lib/openat.c
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/openat.c,v
retrieving revision 1.13
diff -p -u -r1.13 openat.c
--- lib/openat.c        13 Sep 2006 22:38:14 -0000      1.13
+++ lib/openat.c        30 Sep 2006 00:35:30 -0000
@@ -85,14 +85,23 @@ openat_permissive (int fd, char const *f
     return open (file, flags, mode);
 
   {
-    char *proc_file;
-    BUILD_PROC_NAME (proc_file, fd, file);
-    err = open (proc_file, flags, mode);
-    /* If the syscall succeeds, or if it fails with an unexpected
-       errno value, then return right away.  Otherwise, fall through
-       and resort to using save_cwd/restore_cwd.  */
-    if (0 <= err || ! EXPECTED_ERRNO (errno))
-      return err;
+    char buf[OPENAT_BUFFER_SIZE];
+    char *proc_file = openat_proc_name (buf, fd, file);
+    if (proc_file)
+      {
+       int open_result = open (proc_file, flags, mode);
+       int open_errno = errno;
+       if (proc_file != buf)
+         free (proc_file);
+       /* If the syscall succeeds, or if it fails with an unexpected
+          errno value, then return right away.  Otherwise, fall through
+          and resort to using save_cwd/restore_cwd.  */
+       if (0 <= open_result || ! EXPECTED_ERRNO (open_errno))
+         {
+           errno = open_errno;
+           return open_result;
+         }
+      }
   }
 
   save_ok = (save_cwd (&saved_cwd) == 0);
@@ -128,19 +137,23 @@ openat_permissive (int fd, char const *f
 bool
 openat_needs_fchdir (void)
 {
-  int fd2;
+  bool needs_fchdir = true;
   int fd = open ("/", O_RDONLY);
-  char *proc_file;
 
-  if (fd < 0)
-    return true;
-  BUILD_PROC_NAME (proc_file, fd, ".");
-  fd2 = open (proc_file, O_RDONLY);
-  close (fd);
-  if (0 <= fd2)
-    close (fd2);
+  if (0 <= fd)
+    {
+      char buf[OPENAT_BUFFER_SIZE];
+      char *proc_file = openat_proc_name (buf, fd, ".");
+      if (proc_file)
+       {
+         needs_fchdir = false;
+         if (proc_file != buf)
+           free (proc_file);
+       }
+      close (fd);
+    }
 
-  return fd2 < 0;
+  return needs_fchdir;
 }
 
 #if !HAVE_FDOPENDIR
@@ -164,10 +177,18 @@ fdopendir (int fd)
   int saved_errno;
   DIR *dir;
 
-  char *proc_file;
-  BUILD_PROC_NAME (proc_file, fd, ".");
-  dir = opendir (proc_file);
-  saved_errno = errno;
+  char buf[OPENAT_BUFFER_SIZE];
+  char *proc_file = openat_proc_name (buf, fd, ".");
+  if (proc_file)
+    {
+      dir = opendir (proc_file);
+      saved_errno = errno;
+    }
+  else
+    {
+      dir = NULL;
+      saved_errno = EOPNOTSUPP;
+    }
 
   /* If the syscall fails with an expected errno value, resort to
      save_cwd/restore_cwd.  */
@@ -195,6 +216,8 @@ fdopendir (int fd)
 
   if (dir)
     close (fd);
+  if (proc_file != buf)
+    free (proc_file);
   errno = saved_errno;
   return dir;
 }
Index: m4/openat.m4
===================================================================
RCS file: /cvsroot/gnulib/gnulib/m4/openat.m4,v
retrieving revision 1.7
diff -p -u -r1.7 openat.m4
--- m4/openat.m4        21 Aug 2006 21:46:31 -0000      1.7
+++ m4/openat.m4        30 Sep 2006 00:35:31 -0000
@@ -1,4 +1,4 @@
-#serial 10
+#serial 11
 # See if we need to use our replacement for Solaris' openat et al functions.
 
 dnl Copyright (C) 2004, 2005, 2006 Free Software Foundation, Inc.
@@ -15,6 +15,7 @@ AC_DEFUN([gl_FUNC_OPENAT],
   AC_LIBOBJ([fchmodat])
 
   AC_LIBOBJ([openat-die])
+  AC_LIBOBJ([openat-proc])
   AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
   AC_CHECK_FUNCS_ONCE([lchmod])
   AC_CHECK_FUNCS_ONCE([fdopendir])
Index: modules/openat
===================================================================
RCS file: /cvsroot/gnulib/gnulib/modules/openat,v
retrieving revision 1.13
diff -p -u -r1.13 openat
--- modules/openat      23 Aug 2006 23:07:01 -0000      1.13
+++ modules/openat      30 Sep 2006 00:35:31 -0000
@@ -9,6 +9,7 @@ lib/openat.c
 lib/openat.h
 lib/openat-die.c
 lib/openat-priv.h
+lib/openat-proc.c
 m4/openat.m4
 
 Depends-on:
@@ -18,7 +19,9 @@ gettext-h
 intprops
 lchown
 lstat
+same-inode
 save-cwd
+stdbool
 
 configure.ac:
 gl_FUNC_OPENAT
--- /dev/null   2005-09-24 22:00:15.000000000 -0700
+++ lib/openat-proc.c   2006-09-29 17:30:45.000000000 -0700
@@ -0,0 +1,90 @@
+/* Create /proc/self/fd-related names for subfiles of open directories.
+
+   Copyright (C) 2006 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* Written by Paul Eggert.  */
+
+#include <config.h>
+
+#include "openat-priv.h"
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include <stdio.h>
+#include <string.h>
+
+#include "dirname.h"
+#include "intprops.h"
+#include "same-inode.h"
+#include "xalloc.h"
+
+#define PROC_SELF_FD_FORMAT "/proc/self/fd/%d/%s"
+
+#define PROC_SELF_FD_NAME_SIZE_BOUND(len) \
+  (sizeof PROC_SELF_FD_FORMAT - sizeof "%d%s" \
+   + INT_STRLEN_BOUND (int) + (len) + 1)
+
+
+/* Set BUF to the expansion of PROC_SELF_FD_FORMAT, using FD and FILE
+   respectively for %d and %s.  If successful, return BUF if the
+   result fits in BUF, dynamically allocated memory otherwise.  But
+   return NULL if /proc is not reliable.  */
+char *
+openat_proc_name (char buf[OPENAT_BUFFER_SIZE], int fd, char const *file)
+{
+  static int proc_status = 0;
+
+  if (! proc_status)
+    {
+      /* Set PROC_STATUS to a positive value if /proc/self/fd is
+        reliable, and a negative value otherwise.  Solaris 10
+        /proc/self/fd mishandles "..", and any file name might expand
+        to ".." after symbolic link expansion, so avoid /proc/self/fd
+        if it mishandles "..".  Solaris 10 has openat, but this
+        problem is exhibited on code that built on Solaris 8 and
+        running on Solaris 10.  */
+
+      int proc_self_fd = open ("/proc/self/fd", O_RDONLY);
+      if (proc_self_fd < 0)
+       proc_status = -1;
+      else
+       {
+         struct stat proc_self_fd_dotdot_st;
+         struct stat proc_self_st;
+         char dotdot_buf[PROC_SELF_FD_NAME_SIZE_BOUND (sizeof ".." - 1)];
+         sprintf (dotdot_buf, PROC_SELF_FD_FORMAT, proc_self_fd, "..");
+         proc_status =
+           ((stat (dotdot_buf, &proc_self_fd_dotdot_st) == 0
+             && stat ("/proc/self", &proc_self_st) == 0
+             && SAME_INODE (proc_self_fd_dotdot_st, proc_self_st))
+            ? 1 : -1);
+         close (proc_self_fd);
+       }
+    }
+
+  if (proc_status < 0)
+    return NULL;
+  else
+    {
+      size_t bufsize = PROC_SELF_FD_NAME_SIZE_BOUND (strlen (file));
+      char *result = (bufsize < OPENAT_BUFFER_SIZE ? buf : xmalloc (bufsize));
+      sprintf (result, PROC_SELF_FD_FORMAT, fd, file);
+      return result;
+    }
+}




reply via email to

[Prev in Thread] Current Thread [Next in Thread]