ext4: verify group number in verify_group_input() before using it

Check the group number for sanity earilier, before calling routines
such as ext4_bg_has_super() or ext4_group_overhead_blocks().

Reported-by: Jonathan Salwan <jonathan.salwan@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 11 insertions, 6 deletions

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index b27c96d01965..6ed4df27da8d 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -79,12 +79,20 @@ static int verify_group_input(struct super_block *sb,
         ext4_fsblk_t end = start + input->blocks_count;
         ext4_group_t group = input->group;
         ext4_fsblk_t itend = input->inode_table + sbi->s_itb_per_group;
-        unsigned overhead = ext4_group_overhead_blocks(sb, group);
-        ext4_fsblk_t metaend = start + overhead;
+        unsigned overhead;
+        ext4_fsblk_t metaend;
         struct buffer_head *bh = NULL;
         ext4_grpblk_t free_blocks_count, offset;
         int err = -EINVAL;
 
+        if (group != sbi->s_groups_count) {
+                ext4_warning(sb, "Cannot add at group %u (only %u groups)",
+                             input->group, sbi->s_groups_count);
+                return -EINVAL;
+        }
+
+        overhead = ext4_group_overhead_blocks(sb, group);
+        metaend = start + overhead;
         input->free_blocks_count = free_blocks_count =
                 input->blocks_count - 2 - overhead - sbi->s_itb_per_group;
 
@@ -96,10 +104,7 @@ static int verify_group_input(struct super_block *sb,
                        free_blocks_count, input->reserved_blocks);
 
         ext4_get_group_no_and_offset(sb, start, NULL, &offset);
-        if (group != sbi->s_groups_count)
-                ext4_warning(sb, "Cannot add at group %u (only %u groups)",
-                             input->group, sbi->s_groups_count);
-        else if (offset != 0)
+        if (offset != 0)
                         ext4_warning(sb, "Last group not full");
         else if (input->reserved_blocks > input->blocks_count / 5)
                 ext4_warning(sb, "Reserved blocks too high (%u)",