linux-kernel - [PATCH v2] module: Fix display of wrong module .text address

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Date:   Wed, 18 Apr 2018 08:39:04 +0200
From:   Thomas Richter <tmricht@...ux.ibm.com>
To:     jeyu@...nel.org, torvalds@...ux-foundation.org,
        linux-kernel@...r.kernel.org
Cc:     borntraeger@...ibm.com, schwidefsky@...ibm.com,
        brueckner@...ux.vnet.ibm.com, heiko.carstens@...ibm.com,
        peterz@...radead.org, acme@...nel.org, me@...in.cc,
        keescook@...omium.org, stable@...r.kernel.org,
        Thomas Richter <tmricht@...ux.ibm.com>
Subject: [PATCH v2] module: Fix display of wrong  module .text address

Fixes: ef0010a30935 ("vsprintf: don't use 'restricted_pointer()'
when not restricting") for /sys/module/*/sections/.text file.

Reading file /proc/modules shows the correct address:
[root@...lp76 ~]# cat /proc/modules | egrep '^qeth_l2'
qeth_l2 94208 1 - Live 0x000003ff80401000

and reading file /sys/module/qeth_l2/sections/.text
[root@...lp76 ~]# cat /sys/module/qeth_l2/sections/.text
0x0000000018ea8363
displays a random address.

This breaks the perf tool which uses this address on s390
to calculate start of .text section in memory.

Fix this by printing the correct (unhashed) address.

Thanks to Jessica Yu for helping on this.

Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Thomas Richter <tmricht@...ux.ibm.com>
Cc: Jessica Yu <jeyu@...nel.org>
Cc: stable@...r.kernel.org
---
 kernel/module.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/module.c b/kernel/module.c
index a6e43a5806a1..40b42000bd80 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1472,7 +1472,8 @@ static ssize_t module_sect_show(struct module_attribute *mattr,
 {
 	struct module_sect_attr *sattr =
 		container_of(mattr, struct module_sect_attr, mattr);
-	return sprintf(buf, "0x%pK\n", (void *)sattr->address);
+	return sprintf(buf, "0x%px\n", kptr_restrict < 2 ?
+		       (void *)sattr->address : 0);
 }
 
 static void free_sect_attrs(struct module_sect_attrs *sect_attrs)
-- 
2.14.3