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SubjectRe: Possible race in loop.ko
On Fri, Jul 28, 2017 at 11:55 PM, Anton Volkov <avolkov@ispras.ru> wrote:
> Hello.
> While searching for races in Linux kernel I've come across
> drivers/block/loop.ko module. Here is the question that I came up with while
> analyzing results. Lines are given using the info from Linux v4.12.
>
> In loop_init function additional initialization happens after a successful
> call to misc_register() (loop.c: line 1961). Consider the following case:
>
> Thread 1: Thread 2:
> loop_init()
> misc_register() loop_control_ioctl
> part_shift = 0 -> loop_add
> if (max_part > 0) { alloc_disk(1 << part_shift)
> part_shift =
> <greater than 0>
> ...
> }
>
> In this case alloc_disk() will be called with 1 as a parameter although
> part_shift should have been greater than 0. Maybe it would be better to move
> the call to a misc_register() function a bit further down (at least so it
> could be after the part_shift initialization)?

That looks a good idea, could you cook a patch to do it?


--
Ming Lei

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