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SubjectRe: [PATCH] Driver Core patches for 2.6.10-rc1
Date
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ChangeSet 1.2450, 2004/11/01 13:06:02-08:00, kay.sievers@vrfy.org

[PATCH] kobject: fix hotplug bug with seqnum

On Sat, Oct 30, 2004 at 04:54:29AM +0200, Kay Sievers wrote:
> On Sat, Oct 30, 2004 at 02:25:23AM +0200, Kay Sievers wrote:
> > On Sat, Oct 30, 2004 at 02:00:45AM +0200, Kay Sievers wrote:
> > > On Fri, Oct 29, 2004 at 06:13:19PM -0500, Greg KH wrote:
> > > > On Fri, Oct 29, 2004 at 11:28:56PM +0200, Kay Sievers wrote:
> > > > > > But there might still be a problem. With this change, the sequence
> > > > > > number is not sent out the kevent message. Kay, do you think this is an
> > > > > > issue? I don't think we can get netlink messages out of order, right?
> > > > >
> > > > > Right, especially not the events with the same DEVPATH, like "remove"
> > > > > beating an "add". But I'm not sure if the number isn't useful. Whatever
> > > > > we may do with the hotplug over netlink in the future, we will only have
> > > > > /sbin/hotplug for the early boot and it may be nice to know, what events
> > > > > we have already handled...
> > > > >
> > > > > > I'll hold off on applying this patch until we figure this out...
> > > > >
> > > > > How about just reserving 20 bytes for the number (u64 will never be
> > > > > more than that), save the pointer to that field, and fill the number in
> > > > > later?
> > > >
> > > > Ah, something like this instead? I like it, it's even smaller than the
> > > > previous patch. Compile tested only...
> > >
> > > I like that. How about the following. It will keep the buffer clean from
> > > random chars, cause the kevent does not have the vector and relies on
> > > the '\0' to separate the strings from each other.
> > > I've tested it. The netlink-hotplug message looks like this:
> > >
> > > recv(3, "remove@/class/input/mouse2\0ACTION=remove\0DEVPATH=/class/input/mouse2\0SUBSYSTEM=input\0SEQNUM=961 \0", 1024, 0) = 113
> >
> > Hmm, these trailing spaces are just bad, sorry. I'll better pass the
> > envp array over to send_uevent() and clean up the keys while copying
> > the env values into the skb buffer. This will make the event payload
> > more safe too. So your first version looks better.
>
> How about this? We copy over key by key into the skb buffer and the
> netlink message can get the envp array without depending on a single
> continuous buffer.
>
> The netlink message looks nice like this now:
>
> recv(3, "
> add@/devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2:1.0\0
> HOME=/\0
> PATH=/sbin:/bin:/usr/sbin:/usr/bin\0
> ACTION=add\0
> DEVPATH=/devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2:1.0\0
> SUBSYSTEM=usb\0
> SEQNUM=991\0
> DEVICE=/proc/bus/usb/003/008\0
> PRODUCT=46d/c03e/2000\0
> TYPE=0/0/0\0
> INTERFACE=3/1/2\0
> ", 1024, 0) = 268

Here is an improved version that uses skb_put() to fill the skb buffer,
instead of trimming the buffer to the final size after we've copied over
all keys.


Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>


lib/kobject_uevent.c | 47 ++++++++++++++++++++++++++++++-----------------
1 files changed, 30 insertions(+), 17 deletions(-)

diff -Nru a/lib/kobject_uevent.c b/lib/kobject_uevent.c
--- a/lib/kobject_uevent.c 2004-11-01 13:36:12 -08:00
+++ b/lib/kobject_uevent.c 2004-11-01 13:36:12 -08:00
@@ -23,6 +23,9 @@
#include <linux/kobject.h>
#include <net/sock.h>

+#define BUFFER_SIZE 1024 /* buffer for the hotplug env */
+#define NUM_ENVP 32 /* number of env pointers */
+
#if defined(CONFIG_KOBJECT_UEVENT) || defined(CONFIG_HOTPLUG)
static char *action_to_string(enum kobject_action action)
{
@@ -53,12 +56,11 @@
*
* @signal: signal name
* @obj: object path (kobject)
- * @buf: buffer used to pass auxiliary data like the hotplug environment
- * @buflen:
- * gfp_mask:
+ * @envp: possible hotplug environment to pass with the message
+ * @gfp_mask:
*/
-static int send_uevent(const char *signal, const char *obj, const void *buf,
- int buflen, int gfp_mask)
+static int send_uevent(const char *signal, const char *obj,
+ char **envp, int gfp_mask)
{
struct sk_buff *skb;
char *pos;
@@ -69,16 +71,25 @@

len = strlen(signal) + 1;
len += strlen(obj) + 1;
- len += buflen;

- skb = alloc_skb(len, gfp_mask);
+ /* allocate buffer with the maximum possible message size */
+ skb = alloc_skb(len + BUFFER_SIZE, gfp_mask);
if (!skb)
return -ENOMEM;

pos = skb_put(skb, len);
+ sprintf(pos, "%s@%s", signal, obj);

- pos += sprintf(pos, "%s@%s", signal, obj) + 1;
- memcpy(pos, buf, buflen);
+ /* copy the environment key by key to our continuous buffer */
+ if (envp) {
+ int i;
+
+ for (i = 2; envp[i]; i++) {
+ len = strlen(envp[i]) + 1;
+ pos = skb_put(skb, len);
+ strcpy(pos, envp[i]);
+ }
+ }

return netlink_broadcast(uevent_sock, skb, 0, 1, gfp_mask);
}
@@ -107,10 +118,10 @@
if (!attrpath)
goto exit;
sprintf(attrpath, "%s/%s", path, attr->name);
- rc = send_uevent(signal, attrpath, NULL, 0, gfp_mask);
+ rc = send_uevent(signal, attrpath, NULL, gfp_mask);
kfree(attrpath);
} else {
- rc = send_uevent(signal, path, NULL, 0, gfp_mask);
+ rc = send_uevent(signal, path, NULL, gfp_mask);
}

exit:
@@ -169,8 +180,6 @@
u64 hotplug_seqnum;
static spinlock_t sequence_lock = SPIN_LOCK_UNLOCKED;

-#define BUFFER_SIZE 1024 /* should be enough memory for the env */
-#define NUM_ENVP 32 /* number of env pointers */
/**
* kobject_hotplug - notify userspace by executing /sbin/hotplug
*
@@ -182,6 +191,7 @@
char *argv [3];
char **envp = NULL;
char *buffer = NULL;
+ char *seq_buff;
char *scratch;
int i = 0;
int retval;
@@ -258,6 +268,11 @@
envp [i++] = scratch;
scratch += sprintf(scratch, "SUBSYSTEM=%s", name) + 1;

+ /* reserve space for the sequence,
+ * put the real one in after the hotplug call */
+ envp[i++] = seq_buff = scratch;
+ scratch += strlen("SEQNUM=18446744073709551616") + 1;
+
if (hotplug_ops->hotplug) {
/* have the kset specific function add its stuff */
retval = hotplug_ops->hotplug (kset, kobj,
@@ -273,15 +288,13 @@
spin_lock(&sequence_lock);
seq = ++hotplug_seqnum;
spin_unlock(&sequence_lock);
-
- envp [i++] = scratch;
- scratch += sprintf(scratch, "SEQNUM=%lld", (long long)seq) + 1;
+ sprintf(seq_buff, "SEQNUM=%lld", (long long)seq);

pr_debug ("%s: %s %s seq=%lld %s %s %s %s %s\n",
__FUNCTION__, argv[0], argv[1], (long long)seq,
envp[0], envp[1], envp[2], envp[3], envp[4]);

- send_uevent(action_string, kobj_path, buffer, scratch - buffer, GFP_KERNEL);
+ send_uevent(action_string, kobj_path, envp, GFP_KERNEL);

if (!hotplug_path[0])
goto exit;
-
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