During ext4 mount api rework the commit e6e268cb6822 ("ext4: move quota
configuration out of handle_mount_opt()") introduced a bug where we
would kfree(sbi->s_qf_names[i]) before assigning the new quota name in
ext4_apply_quota_options().
This is wrong because we're using kfree() on rcu prointer that could be
simultaneously accessed from ext4_show_quota_options() during remount.
Fix it by using rcu_replace_pointer() to replace the old qname with the
new one and then kfree_rcu() the old quota name.
Also use get_qf_name() instead of sbi->s_qf_names in strcmp() to silence
the sparse warning.
Fixes: e6e268cb6822 ("ext4: move quota configuration out of handle_mount_opt()")
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
---
fs/ext4/super.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index b72d989b77fb..acb0c58cd3d1 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2633,8 +2633,10 @@ static void ext4_apply_quota_options(struct fs_context *fc,
qname = ctx->s_qf_names[i]; /* May be NULL */
ctx->s_qf_names[i] = NULL;
- kfree(sbi->s_qf_names[i]);
- rcu_assign_pointer(sbi->s_qf_names[i], qname);
+ qname = rcu_replace_pointer(sbi->s_qf_names[i], qname,
+ lockdep_is_held(&sb->s_umount));
+ if (qname)
+ kfree_rcu(qname);
set_opt(sb, QUOTA);
}
}
@@ -2688,7 +2690,7 @@ static int ext4_check_quota_consistency(struct fs_context *fc,
goto err_jquota_change;
if (sbi->s_qf_names[i] && ctx->s_qf_names[i] &&
- strcmp(sbi->s_qf_names[i],
+ strcmp(get_qf_name(sb, sbi, i),
ctx->s_qf_names[i]) != 0)
goto err_jquota_specified;
}
--
2.31.1
