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gfs2: Refcounting fix in gfs2_thaw_super

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[ 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.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Andreas Gruenbacher 2023-12-25 20:07:46 +01:00 • committed by Greg Kroah-Hartman
parent 3cde81f8ad
commit 73567149be
1 changed files with 2 additions and 0 deletions
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fs/gfs2/super.c
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@ -819,6 +819,7 @@ static int gfs2_thaw_super(struct super_block *sb, enum freeze_holder who)
if (!test_bit(SDF_FREEZE_INITIATOR, &sdp->sd_flags)) if (!test_bit(SDF_FREEZE_INITIATOR, &sdp->sd_flags))
goto out; goto out;
atomic_inc(&sb->s_active);
gfs2_freeze_unlock(&sdp->sd_freeze_gh); gfs2_freeze_unlock(&sdp->sd_freeze_gh);
error = gfs2_do_thaw(sdp); error = gfs2_do_thaw(sdp);
@ -829,6 +830,7 @@ static int gfs2_thaw_super(struct super_block *sb, enum freeze_holder who)
} }
out: out:
mutex_unlock(&sdp->sd_freeze_mutex); mutex_unlock(&sdp->sd_freeze_mutex);
deactivate_super(sb);
return error; return error;
} }