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Validate mountpoint on path-based unmount using statx

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Use statx to verify that path-based unmounts proceed only if the
mountpoint reported by statx matches the MNTTAB entry reported by
libzfs, aborting the operation if they differ. Align
`zfs umount /path` behavior with `zfs umount dataset`.

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Ameer Hamza <ahamza@ixsystems.com>
Closes #17481
This commit is contained in:
Ameer Hamza 2025-07-09 07:10:00 +05:00 committed by Alexander Motin
parent 7e945a5b3f
commit 21d5f25724
5 changed files with 89 additions and 6 deletions
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19
cmd/zfs/zfs_main.c
View File

@ -7716,6 +7716,7 @@ 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.
@ -7757,6 +7758,24 @@ 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];

34
config/user-statx.m4 Normal file
View File

@ -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
config/user.m4
View File

@ -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

5
lib/libspl/include/os/linux/sys/stat.h
View File

@ -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().
*/

36
lib/libspl/os/linux/getmntany.c
View File

@ -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;
@ -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");
@ -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);
@ -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);