debugfs: Fix debugfs_read_file_str()

Read the entire size of the buffer, including the trailing new line
character.
Discovered while reading the sched domain names of CPU0:

before:

cat /sys/kernel/debug/sched/domains/cpu0/domain*/name
SMTMCDIE

after:

cat /sys/kernel/debug/sched/domains/cpu0/domain*/name
SMT
MC
DIE

Fixes: 9af0440ec86eb ("debugfs: Implement debugfs_create_str()")
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/20210527091105.258457-1-dietmar.eggemann@arm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index e813acf..ba7c01c 100644 (file)
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -893,7 +893,7 @@ ssize_t debugfs_read_file_str(struct file *file, char __user *user_buf,
 
        copy[copy_len] = '\n';
 
-       ret = simple_read_from_buffer(user_buf, count, ppos, copy, copy_len);
+       ret = simple_read_from_buffer(user_buf, count, ppos, copy, len);
        kfree(copy);
 
        return ret;