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[PATCH] kernel/module.c - fix warning and reduce stack usage - reintroduction of mistakenly dropped patch

 

 

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juhl-lkml at dif

Apr 2, 2005, 3:57 PM

Post #1 of 4 (325 views)
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[PATCH] kernel/module.c - fix warning and reduce stack usage - reintroduction of mistakenly dropped patch

Hi Andrew,

Reading your 2.6.12-rc1-mm4 announce text I see

...
-figure-out-who-is-inserting-bogus-modules-warning-fix.patch

Folded into figure-out-who-is-inserting-bogus-modules.patch
...
figure-out-who-is-inserting-bogus-modules.patch
Figure out who is inserting bogus modules
...

However, it seems you did *not* roll
figure-out-who-is-inserting-bogus-modules-warning-fix.patch into
figure-out-who-is-inserting-bogus-modules.patch but instead just dropped
the patch.

It also turns out I had a small boundary error (off-by-one) in my original
patch which Yum Rayan spotted and fixed in a patch he wrote that also
reduces the stack usage of the function (by dynamically allocating the
needed mem for 'args' instead of using a static 512 byte array - see the
LKML thread with subject "[PATCH] Reduce stack usage in module.c"), so
below you'll find an updated patch that reintroduce
figure-out-who-is-inserting-bogus-modules-warning-fix.patch on top of
2.6.12-rc1-mm4 and includes Yum Rayan's fix for the off-by-one and also
adopts his use of kmalloc() instead of large static array.

Yum Rayan's patch does more than what I've included below, I've only
included his changes to the who_is_doing_it() function, if you want the
rest of his changes then please see the original thread for his full
patch.

Here's the updated figure-out-who-is-inserting-bogus-modules-warning-fix.patch

Signed-off-by: Jesper Juhl <juhl-lkml[at]dif.dk>

--- linux-2.6.12-rc1-mm4-orig/kernel/module.c 2005-03-31 21:20:07.000000000 +0200
+++ linux-2.6.12-rc1-mm4/kernel/module.c 2005-04-03 01:54:30.000000000 +0200
@@ -1399,10 +1399,19 @@ static inline void add_kallsyms(struct m
static void who_is_doing_it(void)
{
/* Print out all the args. */
- char args[512];
- unsigned int i, len = current->mm->arg_end - current->mm->arg_start;
+ char *args;
+ unsigned long i, len = current->mm->arg_end - current->mm->arg_start;

- copy_from_user(args, (void *)current->mm->arg_start, len);
+ if (len > 512)
+ len = 512;
+
+ args = kmalloc(len + 1, GFP_KERNEL);
+ if (!args) {
+ printk(KERN_WARNING "Unable to allocate memory, can't print who's inserting bogus modules\n");
+ return;
+ }
+
+ len -= copy_from_user(args, (void *)current->mm->arg_start, len);

for (i = 0; i < len; i++) {
if (args[i] == '\0')
@@ -1410,6 +1419,7 @@ static void who_is_doing_it(void)
}
args[i] = 0;
printk("ARGS: %s\n", args);
+ kfree(args);
}

/* Allocate and load the module: note that size of section 0 is always


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juhl-lkml at dif

Apr 2, 2005, 3:05 PM

Post #2 of 4 (305 views)
Permalink
Re: [PATCH] kernel/module.c - fix warning and reduce stack usage - reintroduction of mistakenly dropped patch [In reply to]

On Sun, 3 Apr 2005, Jesper Juhl wrote:

>
> Hi Andrew,
>
> Reading your 2.6.12-rc1-mm4 announce text I see
>
> ...
> -figure-out-who-is-inserting-bogus-modules-warning-fix.patch
>
> Folded into figure-out-who-is-inserting-bogus-modules.patch
> ...
> figure-out-who-is-inserting-bogus-modules.patch
> Figure out who is inserting bogus modules
> ...
>
> However, it seems you did *not* roll
> figure-out-who-is-inserting-bogus-modules-warning-fix.patch into
> figure-out-who-is-inserting-bogus-modules.patch but instead just dropped
> the patch.
>
> It also turns out I had a small boundary error (off-by-one) in my original
> patch which Yum Rayan spotted and fixed in a patch he wrote that also
> reduces the stack usage of the function (by dynamically allocating the
> needed mem for 'args' instead of using a static 512 byte array - see the
> LKML thread with subject "[PATCH] Reduce stack usage in module.c"), so
> below you'll find an updated patch that reintroduce
> figure-out-who-is-inserting-bogus-modules-warning-fix.patch on top of
> 2.6.12-rc1-mm4 and includes Yum Rayan's fix for the off-by-one and also
> adopts his use of kmalloc() instead of large static array.
>
> Yum Rayan's patch does more than what I've included below, I've only
> included his changes to the who_is_doing_it() function, if you want the
> rest of his changes then please see the original thread for his full
> patch.
>
> Here's the updated figure-out-who-is-inserting-bogus-modules-warning-fix.patch
>
In case you prefer the static array, so the function will never fail due
to OOM, then here's an alternative version of my original patch /with/ the
static array but /without/ the off-by-one error :

Signed-off-by: Jesper Juhl <juhl-lkml[at]dif.dk>

--- linux-2.6.12-rc1-mm4-orig/kernel/module.c 2005-03-31 21:20:07.000000000 +0200
+++ linux-2.6.12-rc1-mm4/kernel/module.c 2005-04-03 02:04:39.000000000 +0200
@@ -1400,9 +1400,12 @@ static void who_is_doing_it(void)
{
/* Print out all the args. */
char args[512];
- unsigned int i, len = current->mm->arg_end - current->mm->arg_start;
+ unsigned long i, len = current->mm->arg_end - current->mm->arg_start;

- copy_from_user(args, (void *)current->mm->arg_start, len);
+ if (len > 511)
+ len = 511;
+
+ len -= copy_from_user(args, (void *)current->mm->arg_start, len);

for (i = 0; i < len; i++) {
if (args[i] == '\0')


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juhl-lkml at dif

Apr 2, 2005, 3:06 PM

Post #3 of 4 (306 views)
Permalink
Re: [PATCH] kernel/module.c - fix warning and reduce stack usage - reintroduction of mistakenly dropped patch [In reply to]

On Sat, 2 Apr 2005, Andrew Morton wrote:

> Jesper Juhl <juhl-lkml[at]dif.dk> wrote:
> >
> > However, it seems you did *not* roll
> > figure-out-who-is-inserting-bogus-modules-warning-fix.patch into
> > figure-out-who-is-inserting-bogus-modules.patch but instead just dropped
> > the patch.
>
> I meant to drop it - it was just a debug thing, and we fixed the bug ages
> ago and people kept on trying to fix the debug patch.
>
Ohh, I see. Then please disregard the mail I just send with an alternative
version.

--
Jesper


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akpm at osdl

Apr 2, 2005, 3:57 PM

Post #4 of 4 (297 views)
Permalink
Re: [PATCH] kernel/module.c - fix warning and reduce stack usage - reintroduction of mistakenly dropped patch [In reply to]

Jesper Juhl <juhl-lkml[at]dif.dk> wrote:
>
> However, it seems you did *not* roll
> figure-out-who-is-inserting-bogus-modules-warning-fix.patch into
> figure-out-who-is-inserting-bogus-modules.patch but instead just dropped
> the patch.

I meant to drop it - it was just a debug thing, and we fixed the bug ages
ago and people kept on trying to fix the debug patch.

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Please read the FAQ at http://www.tux.org/lkml/

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