From: Tuo Li islituo@gmail.com
[ 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_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: BassCheck bass@buaa.edu.cn Signed-off-by: Tuo Li islituo@gmail.com Signed-off-by: Andreas Gruenbacher agruenba@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/gfs2/super.c | 26 +++++++++++++++----------- 1 file changed, 15 insertions(+), 11 deletions(-)
diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c index ca6ee1cbccd50..51b44da4a0d64 100644 --- a/fs/gfs2/super.c +++ b/fs/gfs2/super.c @@ -980,7 +980,14 @@ 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"); @@ -1035,17 +1042,14 @@ 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) {