Messages in this thread | | | Date | Wed, 30 Mar 2005 10:01:04 -0800 | From | "Randy.Dunlap" <> | Subject | Re: [PATCH] Reduce stack usage in module.c |
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Yum Rayan wrote: > On Tue, 29 Mar 2005 09:43:12 -0800, Randy.Dunlap <rddunlap@osdl.org> wrote: > >>Yum Rayan wrote: >> >>>Attempt to reduce stack usage in module.c (linux-2.6.12-rc1-mm3). >>>Specifically from checkstack.pl > >>>Also while at it, fix following in who_is_doing_it(...) >>>- use only as much memory is needed >>>- do not write past array index for the boundary case >> >>I don't see a boundary case problem with the current code, >>hence I don't see why the kmalloc(len + 1, GFP_KERNEL) is >>needed... > > > Let's consider the original code and len = 513 > > 1399 static void who_is_doing_it(void) > 1400 { > 1401 /* Print out all the args. */ > 1402 char args[512]; > 1403 unsigned long i, len = current->mm->arg_end - > current->mm->arg_start; > 1404 > 1405 if (len > 512) > 1406 len = 512; > 1407 > 1408 len -= copy_from_user(args, (void > *)current->mm->arg_start, len); > 1409 > 1410 for (i = 0; i < len; i++) { > 1411 if (args[i] == '\0') > 1412 args[i] = ' '; > 1413 } > 1414 args[i] = 0; > 1415 printk("ARGS: %s\n", args); > 1416 } > > After lines 1410 thru 1413, "i" wil be 512. So line 1414 will be > "args[512] = 0". But args is 512 byte array with last legally > accessible element at 511?
Yes, it's so obvious (now). :)
>>File names start one level deeper than wanted. They should begin >>with linux/ or a/ or ./ e.g. >>There are plenty of docs on this, please let me know if you need >>references to them. > > > Point noted. Will post patch to linux/Documentation/SubmittingPatches, > hopefully making it more clear. Reworked patch at end of email.
Good idea, thanks.
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