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From:   Fox Chen <foxhlchen@gmail.com>
To:     rpeterso@redhat.com, agruenba@redhat.com
Cc:     Fox Chen <foxhlchen@gmail.com>, cluster-devel@redhat.com,
        linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org
Subject: [PATCH] gfs2: gfs2_read_sb: put gfs2_assert inside the loop
Date:   Sat,  3 Oct 2020 14:31:43 +0800
Message-Id: <20201003063143.13093-1-foxhlchen@gmail.com>
MIME-Version: 1.0
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for (x = 2;; x++) {
        ...
        gfs2_assert(sdp, x <= GFS2_MAX_META_HEIGHT);  <--- after
        ...
        if (d != sdp->sd_heightsize[x - 1] || m)
                break;
        sdp->sd_heightsize[x] = space;
}

sdp->sd_max_height = x
gfs2_assert(sdp, sdp->sd_max_height <= GFS2_MAX_META_HEIGHT) <--- before

Before this patch, gfs2_assert is put outside of the loop of
sdp->sd_heightsize[x] calculation. When something goes wrong,
x exceeds the size of GFS2_MAX_META_HEIGHT, it may already crash inside
the loop when

sdp->sd_heightsize[x] = space

tries to reach the out-of-bound
location, gfs2_assert won't help here.

This patch fixes this by moving gfs2_assert into the loop.
We will check x value each time to see if it exceeds GFS2_MAX_META_HEIGHT.

Signed-off-by: Fox Chen <foxhlchen@gmail.com>
---
 fs/gfs2/ops_fstype.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index 6d18d2c91add..6cc32e3010f2 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -333,6 +333,7 @@ static int gfs2_read_sb(struct gfs2_sbd *sdp, int silent)
 		u64 space, d;
 		u32 m;
 
+		gfs2_assert(sdp, x <= GFS2_MAX_META_HEIGHT);
 		space = sdp->sd_heightsize[x - 1] * sdp->sd_inptrs;
 		d = space;
 		m = do_div(d, sdp->sd_inptrs);
@@ -343,7 +344,6 @@ static int gfs2_read_sb(struct gfs2_sbd *sdp, int silent)
 	}
 	sdp->sd_max_height = x;
 	sdp->sd_heightsize[x] = ~0;
-	gfs2_assert(sdp, sdp->sd_max_height <= GFS2_MAX_META_HEIGHT);
 
 	sdp->sd_max_dents_per_leaf = (sdp->sd_sb.sb_bsize -
 				      sizeof(struct gfs2_leaf)) /
-- 
2.25.1