ext4: init timer earlier to avoid a kernel panic in __save_error_info

During mount, when we fail to open journal inode or root inode, the
__save_error_info will mod_timer. But actually s_err_report isn't
initialized yet and the kernel oops. The detailed information can
be found https://bugzilla.kernel.org/show_bug.cgi?id=32082.

The best way is to check whether the timer s_err_report is initialized
or not. But it seems that in include/linux/timer.h, we can't find a
good function to check the status of this timer, so this patch just
move the initializtion of s_err_report earlier so that we can avoid
the kernel panic. The corresponding del_timer is also added in the
error path.

Reported-by: Sami Liedes <sliedes@cc.hut.fi>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 5 insertions, 3 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 35bd0206bbb3..551cb8e2110c 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3391,6 +3391,10 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
         get_random_bytes(&sbi->s_next_generation, sizeof(u32));
         spin_lock_init(&sbi->s_next_gen_lock);
 
+        init_timer(&sbi->s_err_report);
+        sbi->s_err_report.function = print_daily_error_info;
+        sbi->s_err_report.data = (unsigned long) sb;
+
         err = percpu_counter_init(&sbi->s_freeblocks_counter,
                         ext4_count_free_blocks(sb));
         if (!err) {
@@ -3652,9 +3656,6 @@ no_journal:
                  "Opts: %s%s%s", descr, sbi->s_es->s_mount_opts,
                  *sbi->s_es->s_mount_opts ? "; " : "", orig_data);
 
-        init_timer(&sbi->s_err_report);
-        sbi->s_err_report.function = print_daily_error_info;
-        sbi->s_err_report.data = (unsigned long) sb;
         if (es->s_error_count)
                 mod_timer(&sbi->s_err_report, jiffies + 300*HZ); /* 5 minutes */
 
@@ -3678,6 +3679,7 @@ failed_mount_wq:
                 sbi->s_journal = NULL;
         }
 failed_mount3:
+        del_timer(&sbi->s_err_report);
         if (sbi->s_flex_groups) {
                 if (is_vmalloc_addr(sbi->s_flex_groups))
                         vfree(sbi->s_flex_groups);