logfs: Prevent memory corruption

This is a bad one.  I wonder whether we were so far protected by
no_free_segments(sb) usually being smaller than LOGFS_NO_AREAS.

Found by Dan Carpenter <[email protected]> using smatch.

Signed-off-by: Joern Engel <[email protected]>
Signed-off-by: Prasad Joshi <[email protected]>

diff --git a/fs/logfs/gc.c b/fs/logfs/gc.c
index caa4419285dcac78e1743a0e2e602eadd57b19bb..d4efb061bdc5d1dd62ecddcb7575cf891e3b792e 100644 (file)
--- a/fs/logfs/gc.c
+++ b/fs/logfs/gc.c
@@ -367,7 +367,7 @@ static struct gc_candidate *get_candidate(struct super_block *sb)
        int i, max_dist;
        struct gc_candidate *cand = NULL, *this;
 
-       max_dist = min(no_free_segments(sb), LOGFS_NO_AREAS);
+       max_dist = min(no_free_segments(sb), LOGFS_NO_AREAS - 1);
 
        for (i = max_dist; i >= 0; i--) {
                this = first_in_list(&super->s_low_list[i]);