On Wed, 11 Jan 2012 15:34:22 -0200
Carlos Maiolino <cmaiolino@xxxxxxxxxx> wrote:
> During a remount of a cifs filesystem, the mtab file is not properly updated, which
> leads to a doubled entry of the same filesystem in the /etc/mtab file. This patch
> adds a new function del_mtab() which is called before the add_mtab() in case the fs
> is being remounted.
> The del_mtab() function will delete from the mtab, the old entry from the filesystem
> which is being remounted, and then, calls add_mtab() to add an updated entry to the
> mtab file.
>
> Signed-off-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
> ---
> mount.cifs.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 98 insertions(+), 0 deletions(-)
>
> diff --git a/mount.cifs.c b/mount.cifs.c
> index 147f7fc..53b2a7d 100644
> --- a/mount.cifs.c
> +++ b/mount.cifs.c
> @@ -42,6 +42,7 @@
> #include <fcntl.h>
> #include <limits.h>
> #include <paths.h>
> +#include <libgen.h>
> #include <sys/mman.h>
> #include <sys/wait.h>
> #ifdef HAVE_LIBCAP_NG
> @@ -161,6 +162,7 @@
> #define OPT_BKUPUID 30
> #define OPT_BKUPGID 31
>
> +#define MNT_TMP_FILE "/.mtab.cifs.XXXXXX"
>
> /* struct for holding parsed mount info for use by privleged process */
> struct parsed_mount_info {
> @@ -1624,6 +1626,97 @@ add_mtab_exit:
> return rc;
> }
>
> +static int
> +del_mtab(char *mountpoint)
> +{
> + int tmprc, rc = 0;
> + FILE *mnttmp, *mntmtab;
> + struct mntent *mountent;
> + char *mtabfile, *mtabdir, *mtabtmpfile;
> +
> + mtabfile = strdup(MOUNTED);
> + mtabdir = dirname(mtabfile);
> + mtabdir = realloc(mtabdir, strlen(mtabdir) + strlen(MNT_TMP_FILE) + 2);
> + if (!mtabdir) {
> + fprintf(stderr, "del_mtab: cannot determine current mtab path");
> + rc = EX_FILEIO;
> + goto del_mtab_exit;
> + }
> +
> + mtabtmpfile = strcat(mtabdir, MNT_TMP_FILE);
> + if (!mtabtmpfile) {
> + fprintf(stderr, "del_mtab: cannot allocate memory to tmp file");
> + rc = EX_FILEIO;
> + goto del_mtab_exit;
> + }
> +
> + atexit(unlock_mtab);
> + rc = lock_mtab();
> + if (rc) {
> + fprintf(stderr, "del_mtab: cannot lock mtab");
> + rc = EX_FILEIO;
> + goto del_mtab_exit;
> + }
> +
> + mtabtmpfile = mktemp(mtabtmpfile);
> + if (!mtabtmpfile) {
> + fprintf(stderr, "del_mtab: cannot setup tmp file destination");
> + rc = EX_FILEIO;
> + goto del_mtab_exit;
> + }
> +
> + mntmtab = setmntent(MOUNTED, "r");
> + if (!mntmtab) {
> + fprintf(stderr, "del_mtab: could not update mount table\n");
> + rc = EX_FILEIO;
> + goto del_mtab_exit;
> + }
> +
> + mnttmp = setmntent(mtabtmpfile, "w");
> + if (!mnttmp) {
> + fprintf(stderr, "del_mtab: could not update mount table\n");
> + endmntent(mntmtab);
> + rc = EX_FILEIO;
> + goto del_mtab_exit;
> + }
> +
> + while ((mountent = getmntent(mntmtab)) != NULL) {
> + if (!strcmp(mountent->mnt_dir,mountpoint))
> + continue;
> + rc = addmntent(mnttmp, mountent);
> + if (rc) {
> + fprintf(stderr, "del_mtab: unable to add mount entry to mtab\n");
> + rc = EX_FILEIO;
> + goto del_mtab_error;
> + }
> + }
> +
> + endmntent(mntmtab);
> +
> + tmprc = my_endmntent(mnttmp, 0);
> + if (tmprc) {
> + fprintf(stderr, "del_mtab: error %d detected on close of tmp file\n",
> + tmprc);
> + rc = EX_FILEIO;
> + goto del_mtab_error;
> + }
> +
> + rename(mtabtmpfile, MOUNTED);
> +
> +del_mtab_exit:
> + unlock_mtab();
> + free(mtabdir);
> + return rc;
> +
> +del_mtab_error:
> + if (unlink(mtabtmpfile))
> + fprintf(stderr, "del_mtab: failed to delete tmp file - %s\n",
> + strerror(errno));
> + unlock_mtab();
> + free(mtabdir);
> + return rc;
You can replace the above 3 lines with "goto del_mtab_exit". That's
better since it consolidates the cleanup code in a single place.
> +}
> +
> /* have the child drop root privileges */
> static int
> drop_child_privs(void)
> @@ -2021,6 +2114,11 @@ mount_retry:
> }
>
> do_mtab:
> + if (parsed_info->flags & MS_REMOUNT){
nit: please add a space between the '(' and '{'.
The above should probably respect the '-n' flag too, and check that the
mtab is usable before trying to change anything. What you might want to
do is move that whole if statement inside the following if statement that
checks nomtab and mtab_unusable.
> + rc = del_mtab(mountpoint);
> + if (rc)
> + goto mount_exit;
> + }
> if (!parsed_info->nomtab && !mtab_unusable())
> rc = add_mtab(orig_dev, mountpoint, parsed_info->flags, fstype);
>
Almost there!
--
Jeff Layton <jlayton@xxxxxxxxx>
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