The patch titled
sysctl: fix up remaining references to uevent_helper()
has been added to the -mm tree. Its filename is
sysctl-fix-up-remaining-references-to-uevent_helper.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: sysctl: fix up remaining references to uevent_helper()
From: Neil Horman <nhorman@xxxxxxxxxxxxx>
Fix up remaining references to uevent_helper to play nice with Andi's
uevent_helper/rcu changes.
Some changes were made recently which modified uevent_helper to be an rcu
protected pointer, rather than a static char array. This has led to a few
missed points in which the sysfs path still assumed that:
1) the uevent_helper symbol could still be accessed safely without
rcu_dereference
2) that the sysfs path could copy data to that pointer safely.
I've fixed this by chaging the sysfs path so that it duplicates the string
on uevent_helper_store, and freeing it (only if it doesn't point to the
CONFIG_DEFAULT_UEVENT_HELPER string), in a call_rcu post-quiescent point.
I've also fixed up the remaining references to the uevent_helper pointers
to use rcu_dereference.
Signed-off-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: Jiri Slaby <jirislaby@xxxxxxxxx>
Cc: Greg KH <gregkh@xxxxxxx>
Cc: Kay Sievers <kay.sievers@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/ksysfs.c | 38 ++++++++++++++++++++++++++++++++++++--
lib/kobject_uevent.c | 4 +++-
2 files changed, 39 insertions(+), 3 deletions(-)
diff -puN kernel/ksysfs.c~sysctl-fix-up-remaining-references-to-uevent_helper kernel/ksysfs.c
--- a/kernel/ksysfs.c~sysctl-fix-up-remaining-references-to-uevent_helper
+++ a/kernel/ksysfs.c
@@ -37,19 +37,53 @@ KERNEL_ATTR_RO(uevent_seqnum);
static ssize_t uevent_helper_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
- return sprintf(buf, "%s\n", uevent_helper);
+ return sprintf(buf, "%s\n", rcu_dereference(uevent_helper));
}
+
+struct uevent_helper_rcu {
+ char *oldptr;
+ struct rcu_head rcu;
+};
+
+static void free_old_uevent_ptr(struct rcu_head *list)
+{
+ struct uevent_helper_rcu *ptr;
+ char *dfl = CONFIG_UEVENT_HELPER_PATH;
+ ptr = container_of(list, struct uevent_helper_rcu, rcu);
+ if (ptr->oldptr && (ptr->oldptr != dfl))
+ kfree(ptr->oldptr);
+
+ kfree(ptr);
+}
+
static ssize_t uevent_helper_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
+ char *kbuf;
+ struct uevent_helper_rcu *old;
+
if (count+1 > UEVENT_HELPER_PATH_LEN)
return -ENOENT;
- memcpy(uevent_helper, buf, count);
+ kbuf = kstrndup(buf, UEVENT_HELPER_PATH_LEN, GFP_KERNEL);
+ if (!kbuf)
+ return -ENOMEM;
uevent_helper[count] = '\0';
if (count && uevent_helper[count-1] == '\n')
uevent_helper[count-1] = '\0';
+ old = kmalloc(sizeof(struct uevent_helper_rcu), GFP_KERNEL);
+ if (!old)
+ goto out_free;
+
+ old->oldptr = rcu_dereference(uevent_helper);
+ rcu_assign_pointer(uevent_helper, kbuf);
+ call_rcu(&old->rcu, free_old_uevent_ptr);
+
return count;
+
+out_free:
+ kfree(kbuf);
+ return -ENOMEM;
}
KERNEL_ATTR_RW(uevent_helper);
#endif
diff -puN lib/kobject_uevent.c~sysctl-fix-up-remaining-references-to-uevent_helper lib/kobject_uevent.c
--- a/lib/kobject_uevent.c~sysctl-fix-up-remaining-references-to-uevent_helper
+++ a/lib/kobject_uevent.c
@@ -126,6 +126,7 @@ int kobject_uevent_env(struct kobject *k
struct kset *kset;
const struct kset_uevent_ops *uevent_ops;
u64 seq;
+ const char *helper;
int i = 0;
int retval = 0;
@@ -272,7 +273,8 @@ int kobject_uevent_env(struct kobject *k
#endif
/* call uevent_helper, usually only enabled during early boot */
- if (uevent_helper[0])
+ helper = rcu_dereference(uevent_helper);
+ if (helper[0])
retval = uevent_call_helper(subsystem, env);
exit:
_
Patches currently in -mm which might be from nhorman@xxxxxxxxxxxxx are
origin.patch
linux-next.patch
coredump-set-group_exit_code-for-other-clone_vm-tasks-too.patch
sysctl-fix-up-remaining-references-to-uevent_helper.patch
kmod-add-init-function-to-usermodehelper.patch
kmod-add-init-function-to-usermodehelper-fix.patch
kmod-replace-call_usermodehelper_pipe-with-use-of-umh-init-function-and-resolve-limit.patch
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