2023-06-13 03:16:30

by Tuo Li

Subject: [PATCH] gfs2: Fix possible data races in gfs2_show_options()

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.

Reported-by: BassCheck <[email protected]>
Signed-off-by: Tuo Li <[email protected]>
---
fs/gfs2/super.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index a84bf6444bba..671adf38fe03 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -1059,6 +1059,7 @@ static int gfs2_show_options(struct seq_file *s, struct dentry *root)
}
if (args->ar_discard)
seq_puts(s, ",discard");
+ spin_lock(&sdp->sd_tune.gt_spin);
val = sdp->sd_tune.gt_logd_secs;
if (val != 30)
seq_printf(s, ",commit=%d", val);
@@ -1070,6 +1071,7 @@ static int gfs2_show_options(struct seq_file *s, struct dentry *root)
val = sdp->sd_tune.gt_quota_quantum;
if (val != 60)
seq_printf(s, ",quota_quantum=%d", val);
+ spin_unlock(&sdp->sd_tune.gt_spin);
if (args->ar_statfs_percent)
seq_printf(s, ",statfs_percent=%d", args->ar_statfs_percent);
if (args->ar_errors != GFS2_ERRORS_DEFAULT) {
--
2.34.1

2023-06-13 12:58:52

by Andreas Gruenbacher

Subject: Re: [PATCH] gfs2: Fix possible data races in gfs2_show_options()

On Tue, Jun 13, 2023 at 5:07 AM Tuo Li <[email protected]> wrote:
> 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.
>
> Reported-by: BassCheck <[email protected]>
> Signed-off-by: Tuo Li <[email protected]>
> ---
> fs/gfs2/super.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
> index a84bf6444bba..671adf38fe03 100644
> --- a/fs/gfs2/super.c
> +++ b/fs/gfs2/super.c
> @@ -1059,6 +1059,7 @@ static int gfs2_show_options(struct seq_file *s, struct dentry *root)
> }
> if (args->ar_discard)
> seq_puts(s, ",discard");
> + spin_lock(&sdp->sd_tune.gt_spin);
> val = sdp->sd_tune.gt_logd_secs;
> if (val != 30)
> seq_printf(s, ",commit=%d", val);
> @@ -1070,6 +1071,7 @@ static int gfs2_show_options(struct seq_file *s, struct dentry *root)
> val = sdp->sd_tune.gt_quota_quantum;
> if (val != 60)
> seq_printf(s, ",quota_quantum=%d", val);
> + spin_unlock(&sdp->sd_tune.gt_spin);
> if (args->ar_statfs_percent)
> seq_printf(s, ",statfs_percent=%d", args->ar_statfs_percent);
> if (args->ar_errors != GFS2_ERRORS_DEFAULT) {
> --
> 2.34.1
>

Added to for-next (with minor adjustments).

Thanks,
Andreas