Preserve errno across _PC_CHOWN_RESTRICTED call on XFS

Fix BZ #15305.

On kernel versions earlier than 2.6.29, the Linux kernel exported a
sysctl called restrict_chown for xfs, which could be used to allow
chown to users other than the owner.  2.6.29 removed this support,
causing the open_not_cancel_2 to fail and thus modify errno.  The fix
is to save and restore errno so that the caller sees it as unmodified.

Additionally, since the code to check the sysctl is not useful on
newer kernels, we add an ifdef so that in future the code block gets
rmeoved completely.

diff --git a/ChangeLog b/ChangeLog
index 3d85c1d..64e9c88 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2013-04-03  Siddhesh Poyarekar  <siddhesh@redhat.com>
+
+       [BZ #15305]
+       * sysdeps/unix/sysv/linux/kernel-features.h
+       [__LINUX_KERNEL_VERSION >= 0x02061d]: Define
+       __ASSUME_XFS_RESTRICTED_CHOWN.
+       * sysdeps/unix/sysv/linux/pathconf.c
+       (__statfs_chown_restricted) [!__ASSUME_XFS_RESTRICTED_CHOWN]:
+       Save and restore errno.
+
 2013-04-02  Joseph Myers  <joseph@codesourcery.com>
 
        [BZ #15327]

diff --git a/NEWS b/NEWS
index 56cdc56..7718a0a 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -12,7 +12,8 @@ Version 2.18
   10357, 11120, 11561, 12723, 13550, 13889, 13951, 14142, 14176, 14200,
   14317, 14327, 14496, 14812, 14920, 14964, 14981, 14982, 14985, 14994,
   14996, 15003, 15006, 15020, 15023, 15036, 15054, 15055, 15062, 15078,
-  15160, 15214, 15232, 15234, 15283, 15285, 15287, 15304, 15307, 15327.
+  15160, 15214, 15232, 15234, 15283, 15285, 15287, 15304, 15305, 15307,
+  15327.
 
 * Add support for calling C++11 thread_local object destructors on thread
   and program exit.  This needs compiler support for offloading C++11

diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h
index 8fdff7e..ccd4c59 100644 (file)
--- a/sysdeps/unix/sysv/linux/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -221,3 +221,9 @@
 #if defined __x86_64__ && __LINUX_KERNEL_VERSION >= 0x030100
 # define __ASSUME_GETCPU_SYSCALL       1
 #endif
+
+/* 2.6.29 removed the XFS restricted_chown sysctl, so it is pointless looking
+   for it in newer kernels.  */
+#if __LINUX_KERNEL_VERSION >= 0x02061d
+# define __ASSUME_XFS_RESTRICTED_CHOWN 1
+#endif

diff --git a/sysdeps/unix/sysv/linux/pathconf.c b/sysdeps/unix/sysv/linux/pathconf.c
index de91a45..723d234 100644 (file)
--- a/sysdeps/unix/sysv/linux/pathconf.c
+++ b/sysdeps/unix/sysv/linux/pathconf.c
@@ -289,11 +289,16 @@ __statfs_chown_restricted (int result, const struct statfs *fsbuf)
       return -1;
     }
 
+#if __ASSUME_XFS_RESTRICTED_CHOWN
+  return 1;
+#else
   int fd;
+  int save_errno;
   long int retval = 1;
   switch (fsbuf->f_type)
     {
     case XFS_SUPER_MAGIC:
+      save_errno = errno;
       /* Read the value from /proc/sys/fs/xfs/restrict_chown.  If we cannot
         read it default to assume the restriction is in place.  */
       fd = open_not_cancel_2 ("/proc/sys/fs/xfs/restrict_chown", O_RDONLY);
@@ -306,6 +311,7 @@ __statfs_chown_restricted (int result, const struct statfs *fsbuf)
 
          close_not_cancel_no_status (fd);
        }
+      __set_errno (save_errno);
       break;
 
     default:
@@ -313,4 +319,5 @@ __statfs_chown_restricted (int result, const struct statfs *fsbuf)
     }
 
   return retval;
+#endif
 }