From: Michael Jeanson <mjeanson@efficios.com>
Date: Thu, 24 Sep 2020 19:38:35 +0000 (-0400)
Subject: fix: Use 'kernel_read' to read from procfs
X-Git-Tag: v2.13.0-rc1~166
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=cc87d2b4fa9348da830b0da09db1ee6653e0d758;p=lttng-modules.git

fix: Use 'kernel_read' to read from procfs

Use the 'kernel_read' helper to read files in procfs, it's present in
the kernel since the 2.6 series and does the right thing on kernels that
require the set_fs dance and newer one which don't.

Change-Id: I1a53fda379e0bb9acc79331626925bbdba63d727
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/src/wrapper/random.c b/src/wrapper/random.c
index 7b91fc7f..63a30988 100644
--- a/src/wrapper/random.c
+++ b/src/wrapper/random.c
@@ -26,21 +26,12 @@ int wrapper_get_bootid(char *bootid)
 	struct file *file;
 	int ret;
 	ssize_t len;
-	mm_segment_t old_fs;
 
 	file = filp_open("/proc/sys/kernel/random/boot_id", O_RDONLY, 0);
 	if (IS_ERR(file))
 		return PTR_ERR(file);
 
-	old_fs = get_fs();
-	set_fs(KERNEL_DS);
-
-	if (!file->f_op || !file->f_op->read) {
-		ret = -EINVAL;
-		goto end;
-	}
-
-	len = file->f_op->read(file, bootid, BOOT_ID_LEN - 1, &file->f_pos);
+	len = kernel_read(file, bootid, BOOT_ID_LEN - 1, &file->f_pos);
 	if (len != BOOT_ID_LEN - 1) {
 		ret = -EINVAL;
 		goto end;
@@ -49,7 +40,6 @@ int wrapper_get_bootid(char *bootid)
 	bootid[BOOT_ID_LEN - 1] = '\0';
 	ret = 0;
 end:
-	set_fs(old_fs);
 	filp_close(file, current->files);
 	return ret;
 }