Hi,

If gfs2 tries to mount a (corrupt) file system that has no resource groups
it still tries to set preferences on the first one, which causes a kernel null
pointer dereference. This patch adds a check to function gfs2_ri_update so
this condition is detected and reported back as an error.

Reported-by: syzbot
Signed-off-by: Bob Peterson <[email protected]>
---
 fs/gfs2/rgrp.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index f7addc6197ed..5e8eef9990e3 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -985,6 +985,10 @@ static int gfs2_ri_update(struct gfs2_inode *ip)
        if (error < 0)
                return error;
 
+       if (RB_EMPTY_ROOT(&sdp->sd_rindex_tree)) {
+               fs_err(sdp, "no resource groups found in the file system.\n");
+               return -ENOENT;
+       }
        set_rgrp_preferences(sdp);
 
        sdp->sd_rindex_uptodate = 1;

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