On Fri Oct 18, 2019 at 10:56 PM Jann Horn wrote:
> The old loop wouldn't stop when reaching `start` if `start==NULL`, instead
> continuing backwards to index -1 and crashing.
>
> Luckily you need to be highly privileged to map things at NULL, so it's not
> a big problem.
>
> Fix it by adjusting the loop so that the loop variable is always in bounds.
>
> This patch is deliberately minimal to simplify backporting, but IMO this
> function could use a refactor. The jump labels in the second loop body are
> horrible (the error gotos should be jumping to free_range instead), and
> both loops would look nicer if they just iterated upwards through indices.
> And the up_read()+mmput() shouldn't be duplicated like that.
>
> Cc: sta...@vger.kernel.org
> Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
> Signed-off-by: Jann Horn <ja...@google.com>
Acked-by: Christian Brauner <christian.brau...@ubuntu.com>
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