[Devel] [PATCH RH9] push_backup: Do not take write lock on ENOTTY

[Kirill Tkhai]

Userspace may pass wrong command. Do not take write lock then.

Signed-off-by: Kirill Tkhai <ktk...@virtuozzo.com>
---
 drivers/md/dm-push-backup.c |   23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/drivers/md/dm-push-backup.c b/drivers/md/dm-push-backup.c
index 6d7b1859298a..1500d0681cee 100644
--- a/drivers/md/dm-push-backup.c
+++ b/drivers/md/dm-push-backup.c
@@ -329,11 +329,10 @@ static void pb_release_clone(struct request *clone,
        blk_put_request(clone);
 }
 
-static bool msg_wants_down_read(const char *cmd)
+static bool msg_wants_down_write(const char *cmd)
 {
-       if (!strcmp(cmd, "push_backup_read") ||
-           !strcmp(cmd, "push_backup_write") ||
-           !strcmp(cmd, "push_backup_statistics"))
+       if (!strcmp(cmd, "push_backup_start") ||
+           !strcmp(cmd, "push_backup_stop"))
                return true;
 
        return false;
@@ -567,7 +566,7 @@ static int pb_message(struct dm_target *ti, unsigned int 
argc, char **argv,
        struct push_backup *pb = ti->private;
        int ret = -EPERM;
        u64 val, val2;
-       bool read;
+       bool write;
 
        if (!capable(CAP_SYS_ADMIN))
                goto out;
@@ -576,11 +575,11 @@ static int pb_message(struct dm_target *ti, unsigned int 
argc, char **argv,
        if (argc < 1)
                goto out;
 
-       read = msg_wants_down_read(argv[0]);
-       if (read)
-               ret = down_read_killable(&pb->ctl_rwsem);
-       else
+       write = msg_wants_down_write(argv[0]);
+       if (write)
                ret = down_write_killable(&pb->ctl_rwsem);
+       else
+               ret = down_read_killable(&pb->ctl_rwsem);
        if (unlikely(ret))
                goto out;
 
@@ -612,10 +611,10 @@ static int pb_message(struct dm_target *ti, unsigned int 
argc, char **argv,
        }
 
 unlock:
-       if (read)
-               up_read(&pb->ctl_rwsem);
-       else
+       if (write)
                up_write(&pb->ctl_rwsem);
+       else
+               up_read(&pb->ctl_rwsem);
 out:
        return ret;
 }


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