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Validate mountpoint on path-based unmount using statx #17481

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Validate mountpoint on path-based unmount using statx #17481

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19 changes: 19 additions & 0 deletions cmd/zfs/zfs_main.c
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Original file line number Diff line number Diff line change
Expand Up @@ -7729,6 +7729,7 @@ unshare_unmount_path(int op, char *path, int flags, boolean_t is_manual)
struct extmnttab entry;
const char *cmdname = (op == OP_SHARE) ? "unshare" : "unmount";
ino_t path_inode;
char *zfs_mntpnt, *entry_mntpnt;

/*
* Search for the given (major,minor) pair in the mount table.
Expand Down Expand Up @@ -7770,6 +7771,24 @@ unshare_unmount_path(int op, char *path, int flags, boolean_t is_manual)
goto out;
}

/*
* If the filesystem is mounted, check that the mountpoint matches
* the one in the mnttab entry w.r.t. provided path. If it doesn't,
* then we should not proceed further.
*/
entry_mntpnt = strdup(entry.mnt_mountp);
if (zfs_is_mounted(zhp, &zfs_mntpnt)) {
if (strcmp(zfs_mntpnt, entry_mntpnt) != 0) {
(void) fprintf(stderr, gettext("cannot %s '%s': "
"not an original mountpoint\n"), cmdname, path);
free(zfs_mntpnt);
free(entry_mntpnt);
goto out;
}
free(zfs_mntpnt);
}
free(entry_mntpnt);

if (op == OP_SHARE) {
char nfs_mnt_prop[ZFS_MAXPROPLEN];
char smbshare_prop[ZFS_MAXPROPLEN];
Expand Down
34 changes: 34 additions & 0 deletions config/user-statx.m4
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Original file line number Diff line number Diff line change
@@ -0,0 +1,34 @@
dnl #
dnl # Check for statx() function and STATX_MNT_ID availability
dnl #
AC_DEFUN([ZFS_AC_CONFIG_USER_STATX], [
AC_CHECK_HEADERS([linux/stat.h],
[have_stat_headers=yes],
[have_stat_headers=no])

AS_IF([test "x$have_stat_headers" = "xyes"], [
AC_CHECK_FUNC([statx], [
AC_DEFINE([HAVE_STATX], [1], [statx() is available])

dnl Check for STATX_MNT_ID availability
AC_MSG_CHECKING([for STATX_MNT_ID])
AC_COMPILE_IFELSE([
AC_LANG_PROGRAM([[
#include <linux/stat.h>
]], [[
struct statx stx;
int mask = STATX_MNT_ID;
(void)mask;
(void)stx.stx_mnt_id;
]])
], [
AC_MSG_RESULT([yes])
AC_DEFINE([HAVE_STATX_MNT_ID], [1], [STATX_MNT_ID is available])
], [
AC_MSG_RESULT([no])
])
])
], [
AC_MSG_WARN([linux/stat.h not found; skipping statx support])
])
]) dnl end AC_DEFUN
1 change: 1 addition & 0 deletions config/user.m4
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Expand Up @@ -17,6 +17,7 @@ AC_DEFUN([ZFS_AC_CONFIG_USER], [
ZFS_AC_CONFIG_USER_LIBUDEV
ZFS_AC_CONFIG_USER_LIBUUID
ZFS_AC_CONFIG_USER_LIBBLKID
ZFS_AC_CONFIG_USER_STATX
])
ZFS_AC_CONFIG_USER_LIBTIRPC
ZFS_AC_CONFIG_USER_LIBCRYPTO
Expand Down
5 changes: 5 additions & 0 deletions lib/libspl/include/os/linux/sys/stat.h
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,11 @@

#include <sys/mount.h> /* for BLKGETSIZE64 */

#ifdef HAVE_STATX
#include <fcntl.h>
#include <linux/stat.h>
#endif

/*
* Emulate Solaris' behavior of returning the block device size in fstat64().
*/
Expand Down
36 changes: 30 additions & 6 deletions lib/libspl/os/linux/getmntany.c
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Expand Up @@ -85,13 +85,21 @@ _sol_getmntent(FILE *fp, struct mnttab *mgetp)
}

static int
getextmntent_impl(FILE *fp, struct extmnttab *mp)
getextmntent_impl(FILE *fp, struct extmnttab *mp, uint64_t *mnt_id)
{
int ret;
struct stat64 st;

*mnt_id = 0;
ret = _sol_getmntent(fp, (struct mnttab *)mp);
if (ret == 0) {
#ifdef HAVE_STATX_MNT_ID
struct statx stx;
if (statx(AT_FDCWD, mp->mnt_mountp,
AT_STATX_SYNC_AS_STAT | AT_SYMLINK_NOFOLLOW,
STATX_MNT_ID, &stx) == 0 && (stx.stx_mask & STATX_MNT_ID))
*mnt_id = stx.stx_mnt_id;
#endif
if (stat64(mp->mnt_mountp, &st) != 0) {
mp->mnt_major = 0;
mp->mnt_minor = 0;
Expand All @@ -110,6 +118,12 @@ getextmntent(const char *path, struct extmnttab *entry, struct stat64 *statbuf)
struct stat64 st;
FILE *fp;
int match;
boolean_t have_mnt_id = B_FALSE;
uint64_t target_mnt_id = 0;
uint64_t entry_mnt_id;
#ifdef HAVE_STATX_MNT_ID
struct statx stx;
#endif

if (strlen(path) >= MAXPATHLEN) {
(void) fprintf(stderr, "invalid object; pathname too long\n");
Expand All @@ -128,6 +142,13 @@ getextmntent(const char *path, struct extmnttab *entry, struct stat64 *statbuf)
return (-1);
}

#ifdef HAVE_STATX_MNT_ID
if (statx(AT_FDCWD, path, AT_STATX_SYNC_AS_STAT | AT_SYMLINK_NOFOLLOW,
STATX_MNT_ID, &stx) == 0 && (stx.stx_mask & STATX_MNT_ID)) {
have_mnt_id = B_TRUE;
target_mnt_id = stx.stx_mnt_id;
}
#endif

if ((fp = fopen(MNTTAB, "re")) == NULL) {
(void) fprintf(stderr, "cannot open %s\n", MNTTAB);
Expand All @@ -139,12 +160,15 @@ getextmntent(const char *path, struct extmnttab *entry, struct stat64 *statbuf)
*/

match = 0;
while (getextmntent_impl(fp, entry) == 0) {
if (makedev(entry->mnt_major, entry->mnt_minor) ==
statbuf->st_dev) {
match = 1;
break;
while (getextmntent_impl(fp, entry, &entry_mnt_id) == 0) {
if (have_mnt_id) {
match = (entry_mnt_id == target_mnt_id);
} else {
match = makedev(entry->mnt_major, entry->mnt_minor) ==
statbuf->st_dev;
}
if (match)
break;
}
(void) fclose(fp);

Expand Down