Messages in this thread | | | Date | Thu, 25 Feb 2010 09:48:22 +0800 | Subject | Re: [RESEND PATCH] module param_call: fix potential NULL pointer dereference | From | Américo Wang <> |
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On Wed, Feb 24, 2010 at 9:01 AM, Rusty Russell <rusty@rustcorp.com.au> wrote: > On Wed, 24 Feb 2010 02:15:19 am Américo Wang wrote: >> On Tue, Feb 23, 2010 at 02:26:45PM +1030, Rusty Russell wrote: >> >On Mon, 22 Feb 2010 09:10:51 pm Dongdong Deng wrote: >> >> The param_set_fn() function will get a parameter which is a NULL >> >> pointer when insmod module via bare params as following method: >> >> >> >> $insmod foo.ko foo >> >> >> >> If the param_set_fn() function didn't check that parameter and used >> >> it directly, it could caused an OOPS due to NULL pointer dereference. >> >> >> >> The solution is simple: >> >> Using "" to replace NULL parameter, thereby the param_set_fn() >> >> function will never get a NULL pointer. >> > >> >This changes the value of booleans, and loses checking for int params, etc. >> > >> >I liked Americo's approach; I've combined the two approaches below. >> > >> >Since I'm going away, can Andrew take this? >> > >> >Subject: params: don't hand NULL values to param.set callbacks. >> > >> >An audit by Dongdong Deng revealed that most driver-author-written param >> >calls don't handle val == NULL (which happens when parameters are specified >> >with no =, eg "foo" instead of "foo=1"). >> > >> >The only real case to use this is boolean, so handle it specially for that >> >case and remove a source of bugs for everyone else as suggested by Americo. >> > >> >Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> >> >Cc: Dongdong Deng <dongdong.deng@windriver.com> >> >Cc: Américo Wang <xiyou.wangcong@gmail.com> >> > >> >diff --git a/kernel/params.c b/kernel/params.c >> >--- a/kernel/params.c >> >+++ b/kernel/params.c >> >@@ -59,6 +59,9 @@ static int parse_one(char *param, >> > /* Find parameter */ >> > for (i = 0; i < num_params; i++) { >> > if (parameq(param, params[i].name)) { >> >+ /* Noone handled NULL, so do it here. */ >> >+ if (!val && params[i].set != param_set_bool) >> >+ return -EINVAL; >> >> Sorry, after rethinking about this, I think it might be wrong. >> >> With this patch, when I use non-standard bool functions, I will not >> have a chance to use '!val' which should be valid for all bool >> functions. Or am I missing something? > > Sure, at that point we'd need something more sophisticated. But to > fix this properly we want a flags word, and thus something like this > which I worked on earlier: > > http://ozlabs.org/~rusty/kernel/rr-latest/param:param_ops.patch >
Thanks, Rusty!
I love that patch, but since 2.6.33 is already out, can we try to get it merged for 2.6.34? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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