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authorRusty Russell <rusty@rustcorp.com.au>2009-10-29 08:56:16 -0600
committerGreg Kroah-Hartman <gregkh@suse.de>2009-11-09 16:22:17 -0800
commit9f00eee2ffab59cb85ecf1de54282c7fb4669565 (patch)
treee92ca436db4ee3f89004a5018086664bc09926d7
parent05fe6c842ab23f6e823ad87a84adab73ab60beaa (diff)
param: fix lots of bugs with writing charp params from sysfs, by leaking mem.
commit 65afac7d80ab3bc9f81e75eafb71eeb92a3ebdef upstream. e180a6b7759a "param: fix charp parameters set via sysfs" fixed the case where charp parameters written via sysfs were freed, leaving drivers accessing random memory. Unfortunately, storing a flag in the kparam struct was a bad idea: it's rodata so setting it causes an oops on some archs. But that's not all: 1) module_param_array() on charp doesn't work reliably, since we use an uninitialized temporary struct kernel_param. 2) there's a fundamental race if a module uses this parameter and then it's changed: they will still access the old, freed, memory. The simplest fix (ie. for 2.6.32) is to never free the memory. This prevents all these problems, at cost of a memory leak. In practice, there are only 18 places where a charp is writable via sysfs, and all are root-only writable. Reported-by: Takashi Iwai <tiwai@suse.de> Cc: Sitsofe Wheeler <sitsofe@yahoo.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Christof Schmitt <christof.schmitt@de.ibm.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--include/linux/moduleparam.h1
-rw-r--r--kernel/params.c10
2 files changed, 1 insertions, 10 deletions
diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index 6547c3cdbc4c..82a9124f7d75 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -37,7 +37,6 @@ typedef int (*param_set_fn)(const char *val, struct kernel_param *kp);
typedef int (*param_get_fn)(char *buffer, struct kernel_param *kp);
/* Flag bits for kernel_param.flags */
-#define KPARAM_KMALLOCED 1
#define KPARAM_ISBOOL 2
struct kernel_param {
diff --git a/kernel/params.c b/kernel/params.c
index 7f6912ced2ba..276fd63bc780 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -217,13 +217,9 @@ int param_set_charp(const char *val, struct kernel_param *kp)
return -ENOSPC;
}
- if (kp->flags & KPARAM_KMALLOCED)
- kfree(*(char **)kp->arg);
-
/* This is a hack. We can't need to strdup in early boot, and we
* don't need to; this mangled commandline is preserved. */
if (slab_is_available()) {
- kp->flags |= KPARAM_KMALLOCED;
*(char **)kp->arg = kstrdup(val, GFP_KERNEL);
if (!kp->arg)
return -ENOMEM;
@@ -604,11 +600,7 @@ void module_param_sysfs_remove(struct module *mod)
void destroy_params(const struct kernel_param *params, unsigned num)
{
- unsigned int i;
-
- for (i = 0; i < num; i++)
- if (params[i].flags & KPARAM_KMALLOCED)
- kfree(*(char **)params[i].arg);
+ /* FIXME: This should free kmalloced charp parameters. It doesn't. */
}
static void __init kernel_add_sysfs_param(const char *name,