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Commit b4a7ab57 authored by Tuo Li's avatar Tuo Li Committed by Greg Kroah-Hartman
Browse files

gfs2: Fix possible data races in gfs2_show_options() 



[ Upstream commit 6fa0a72cbbe45db4ed967a51f9e6f4e3afe61d20 ]

Some fields such as gt_logd_secs of the struct gfs2_tune are accessed
without holding the lock gt_spin in gfs2_show_options():

  val = sdp->sd_tune.gt_logd_secs;
  if (val != 30)
    seq_printf(s, ",commit=%d", val);

And thus can cause data races when gfs2_show_options() and other functions
such as gfs2_reconfigure() are concurrently executed:

  spin_lock(&gt->gt_spin);
  gt->gt_logd_secs = newargs->ar_commit;

To fix these possible data races, the lock sdp->sd_tune.gt_spin is
acquired before accessing the fields of gfs2_tune and released after these
accesses.

Further changes by Andreas:

- Don't hold the spin lock over the seq_printf operations.

Reported-by: default avatarBassCheck <bass@buaa.edu.cn>
Signed-off-by: default avatarTuo Li <islituo@gmail.com>
Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent c4d5c945

fs/gfs2/super.c

+15 −11
Original line number Diff line number Diff line
@@ -1046,7 +1046,14 @@ static int gfs2_show_options(struct seq_file *s, struct dentry *root) 
{

	struct gfs2_sbd *sdp = root->d_sb->s_fs_info;

	struct gfs2_args *args = &sdp->sd_args;

	int val;

	unsigned int logd_secs, statfs_slow, statfs_quantum, quota_quantum;



	spin_lock(&sdp->sd_tune.gt_spin);

	logd_secs = sdp->sd_tune.gt_logd_secs;

	quota_quantum = sdp->sd_tune.gt_quota_quantum;

	statfs_quantum = sdp->sd_tune.gt_statfs_quantum;

	statfs_slow = sdp->sd_tune.gt_statfs_slow;

	spin_unlock(&sdp->sd_tune.gt_spin);



	if (is_ancestor(root, sdp->sd_master_dir))

		seq_puts(s, ",meta");
@@ -1101,17 +1108,14 @@ static int gfs2_show_options(struct seq_file *s, struct dentry *root) 
	}

	if (args->ar_discard)

		seq_puts(s, ",discard");

	val = sdp->sd_tune.gt_logd_secs;

	if (val != 30)

		seq_printf(s, ",commit=%d", val);

	val = sdp->sd_tune.gt_statfs_quantum;

	if (val != 30)

		seq_printf(s, ",statfs_quantum=%d", val);

	else if (sdp->sd_tune.gt_statfs_slow)

	if (logd_secs != 30)

		seq_printf(s, ",commit=%d", logd_secs);

	if (statfs_quantum != 30)

		seq_printf(s, ",statfs_quantum=%d", statfs_quantum);

	else if (statfs_slow)

		seq_puts(s, ",statfs_quantum=0");

	val = sdp->sd_tune.gt_quota_quantum;

	if (val != 60)

		seq_printf(s, ",quota_quantum=%d", val);

	if (quota_quantum != 60)

		seq_printf(s, ",quota_quantum=%d", quota_quantum);

	if (args->ar_statfs_percent)

		seq_printf(s, ",statfs_percent=%d", args->ar_statfs_percent);

	if (args->ar_errors != GFS2_ERRORS_DEFAULT) {