gfs2: Don't deref jdesc in evict

mainline inclusion
from mainline-v6.4-rc2
commit 504a10d9
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I7CXJL
CVE: CVE-2023-3212

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=504a10d9e46bc37b23d0a1ae2f28973c8516e636

--------------------------------

On corrupt gfs2 file systems the evict code can try to reference the
journal descriptor structure, jdesc, after it has been freed and set to
NULL. The sequence of events is:

init_journal()
...
fail_jindex:
   gfs2_jindex_free(sdp); <------frees journals, sets jdesc = NULL
      if (gfs2_holder_initialized(&ji_gh))
         gfs2_glock_dq_uninit(&ji_gh);
fail:
   iput(sdp->sd_jindex); <--references jdesc in evict_linked_inode
      evict()
         gfs2_evict_inode()
            evict_linked_inode()
               ret = gfs2_trans_begin(sdp, 0, sdp->sd_jdesc->jd_blocks);
<------references the now freed/zeroed sd_jdesc pointer.

The call to gfs2_trans_begin is done because the truncate_inode_pages
call can cause gfs2 events that require a transaction, such as removing
journaled data (jdata) blocks from the journal.

This patch fixes the problem by adding a check for sdp->sd_jdesc to
function gfs2_evict_inode. In theory, this should only happen to corrupt
gfs2 file systems, when gfs2 detects the problem, reports it, then tries
to evict all the system inodes it has read in up to that point.
Reported-by: NYang Lan <lanyang0908@gmail.com>
Signed-off-by: NBob Peterson <rpeterso@redhat.com>
Signed-off-by: NAndreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: NZhaoLong Wang <wangzhaolong1@huawei.com>

Conflicts:
        fs/gfs2/super.c
(cherry picked from commit a1816ee0)

fs/gfs2/super.c

@@ -1412,6 +1412,14 @@ static void gfs2_evict_inode(struct inode *inode)
 	if (inode->i_nlink || sb_rdonly(sb))
 		goto out;
 
+	/*
+	 * In case of an incomplete mount, gfs2_evict_inode() may be called for
+	 * system files without having an active journal to write to.  In that
+	 * case, skip the filesystem evict.
+	 */
+	if (!sdp->sd_jdesc)
+		goto out;
+
 	gfs2_holder_mark_uninitialized(&gh);
 	ret = evict_should_delete(inode, &gh);
 	if (ret == SHOULD_DEFER_EVICTION)