Messages in this thread | | | Date | Tue, 24 Jan 2006 21:46:07 -0500 | From | Benjamin LaHaise <> | Subject | Re: [PATCH -mm] swsusp: userland interface (rev 2) |
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On Wed, Jan 25, 2006 at 12:35:38AM +0100, Rafael J. Wysocki wrote: > > > + if (!access_ok(VERIFY_WRITE, (unsigned long __user *)arg, _IOC_SIZE(cmd))) { > > > + error = -EINVAL; > > > + break; > > > + } > > > > Why do we need an access_ok() here? > > Because we use __put_user() down the road? > > The problem is if the address is wrong we should not try to call > alloc_swap_page() at all. If we did, we wouldn't be able to return the result > and we would leak a swap page.
Then access_ok() is not the droid you are looking for... since it won't catch several cases (out of memory being the most obvious). Doing an early put_user() wouldn't hurt and reduces the chance of later failure even further. __put_user() should never be used outside of a select few performance critical code paths.
-ben -- "Ladies and gentlemen, I'm sorry to interrupt, but the police are here and they've asked us to stop the party." Don't Email: <dont@kvack.org>. - 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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