On Tue, Jan 16, 2024 at 9:53 PM Pavel Machek pavel@denx.de wrote:
Hi!
From: Andreas Gruenbacher agruenba@redhat.com
[ Upstream commit 4e58543e7da4859c4ba61d15493e3522b6ad71fd ]
It turns out that the .freeze_super and .thaw_super operations require the filesystem to manage the superblock refcount itself. We are using the freeze_super() and thaw_super() helpers to mostly take care of that for us, but this means that the superblock may no longer be around by when thaw_super() returns, and gfs2_thaw_super() will then access freed memory. Take an extra superblock reference in gfs2_thaw_super() to fix that.
Patch was broken during backport.
+++ b/fs/gfs2/super.c @@ -1013,6 +1013,7 @@ static int gfs2_freeze(struct super_block *sb) goto out; }
atomic_inc(&sb->s_active); for (;;) { error = gfs2_lock_fs_check_clean(sdp, &sdp->sd_freeze_gh); if (!error)@@ -1034,6 +1035,7 @@ static int gfs2_freeze(struct super_block *sb) error = 0; out: mutex_unlock(&sdp->sd_freeze_mutex);
deactivate_super(sb); return error;}
Notice the goto out? That now jumps around the atomic_inc, but we still do decrease. This will break 4.19, please fix or drop.
Thanks, Pavel.
Sasha, you don't want that fix without "gfs2: Rework freeze / thaw logic" and the follow-up fixes, and backporting that probably isn't going to be worth it.
Thanks, Andreas