tracing: Make splice_read available again

commit e400be674a1a40e9dcb2e95f84d6c1fd2d88f31d upstream.

Since the commit 36e2c7421f02 ("fs: don't allow splice read/write
without explicit ops") is applied to the kernel, splice() and
sendfile() calls on the trace file (/sys/kernel/debug/tracing
/trace) return EINVAL.

This patch restores these system calls by initializing splice_read
in file_operations of the trace file. This patch only enables such
functionalities for the read case.

Link: https://lore.kernel.org/linux-trace-kernel/20230314013707.28814-1-sfoon.kim@samsung.com
Cc: stable@vger.kernel.org
Fixes: 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops")
Signed-off-by: Sung-hun Kim <sfoon.kim@samsung.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f70765780ed3fdb5a36e434a640839d4544dcf1c..888980257340f7a70b803157a5b905aec69297dc 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5120,6 +5120,8 @@ loff_t tracing_lseek(struct file *file, loff_t offset, int whence)
 static const struct file_operations tracing_fops = {
        .open           = tracing_open,
        .read           = seq_read,
+       .read_iter      = seq_read_iter,
+       .splice_read    = generic_file_splice_read,
        .write          = tracing_write_stub,
        .llseek         = tracing_lseek,
        .release        = tracing_release,